TRB - ACRP Report 40 Airport Curbside and Terminal Area Roadway Operations - 2010.pdf

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Airport Curbside and Terminal Area Roadway Operations

Sponsored by the Federal Aviation Administration





James Wilding Metropolitan Washington Airports Authority (retired)

CHAIR: Michael R. Morris, Director of Transportation, North Central Texas Council of Governments, Arlington VICE CHAIR: Neil J. Pedersen, Administrator, Maryland State Highway Administration, Baltimore EXECUTIVE DIRECTOR: Robert E. Skinner, Jr., Transportation Research Board

VICE CHAIR Jeff Hamiel Minneapolis–St. Paul Metropolitan Airports Commission

MEMBERS James Crites Dallas–Fort Worth International Airport Richard de Neufville Massachusetts Institute of Technology Kevin C. Dolliole Unison Consulting John K. Duval Austin Commercial, LP Kitty Freidheim Freidheim Consulting Steve Grossman Jacksonville Aviation Authority Tom Jensen National Safe Skies Alliance Catherine M. Lang Federal Aviation Administration Gina Marie Lindsey Los Angeles World Airports Carolyn Motz Hagerstown Regional Airport Richard Tucker Huntsville International Airport

EX OFFICIO MEMBERS Sabrina Johnson U.S. Environmental Protection Agency Richard Marchi Airports Council International—North America Laura McKee Air Transport Association of America Henry Ogrodzinski National Association of State Aviation Officials Melissa Sabatine American Association of Airport Executives Robert E. Skinner, Jr. Transportation Research Board

SECRETARY Christopher W. Jenks Transportation Research Board

*Membership as of June 2010.

MEMBERS J. Barry Barker, Executive Director, Transit Authority of River City, Louisville, KY Allen D. Biehler, Secretary, Pennsylvania DOT, Harrisburg Larry L. Brown, Sr., Executive Director, Mississippi DOT, Jackson Deborah H. Butler, Executive Vice President, Planning, and CIO, Norfolk Southern Corporation, Norfolk, VA William A.V. Clark, Professor, Department of Geography, University of California, Los Angeles Eugene A. Conti, Jr., Secretary of Transportation, North Carolina DOT, Raleigh Nicholas J. Garber, Henry L. Kinnier Professor, Department of Civil Engineering, and Director, Center for Transportation Studies, University of Virginia, Charlottesville Jeffrey W. Hamiel, Executive Director, Metropolitan Airports Commission, Minneapolis, MN Paula J. Hammond, Secretary, Washington State DOT, Olympia Edward A. (Ned) Helme, President, Center for Clean Air Policy, Washington, DC Adib K. Kanafani, Cahill Professor of Civil Engineering, University of California, Berkeley Susan Martinovich, Director, Nevada DOT, Carson City Debra L. Miller, Secretary, Kansas DOT, Topeka Sandra Rosenbloom, Professor of Planning, University of Arizona, Tucson Tracy L. Rosser, Vice President, Corporate Traffic, Wal-Mart Stores, Inc., Mandeville, LA Steven T. Scalzo, Chief Operating Officer, Marine Resources Group, Seattle, WA Henry G. (Gerry) Schwartz, Jr., Chairman (retired), Jacobs/Sverdrup Civil, Inc., St. Louis, MO Beverly A. Scott, General Manager and Chief Executive Officer, Metropolitan Atlanta Rapid Transit Authority, Atlanta, GA David Seltzer, Principal, Mercator Advisors LLC, Philadelphia, PA Daniel Sperling, Professor of Civil Engineering and Environmental Science and Policy; Director, Institute of Transportation Studies; and Interim Director, Energy Efficiency Center, University of California, Davis Kirk T. Steudle, Director, Michigan DOT, Lansing Douglas W. Stotlar, President and CEO, Con-Way, Inc., Ann Arbor, MI C. Michael Walton, Ernest H. Cockrell Centennial Chair in Engineering, University of Texas, Austin

EX OFFICIO MEMBERS Peter H. Appel, Administrator, Research and Innovative Technology Administration, U.S.DOT J. Randolph Babbitt, Administrator, Federal Aviation Administration, U.S.DOT Rebecca M. Brewster, President and COO, American Transportation Research Institute, Smyrna, GA George Bugliarello, President Emeritus and University Professor, Polytechnic Institute of New York University, Brooklyn; Foreign Secretary, National Academy of Engineering, Washington, DC Anne S. Ferro, Administrator, Federal Motor Carrier Safety Administration, U.S.DOT LeRoy Gishi, Chief, Division of Transportation, Bureau of Indian Affairs, U.S. Department of the Interior, Washington, DC Edward R. Hamberger, President and CEO, Association of American Railroads, Washington, DC John C. Horsley, Executive Director, American Association of State Highway and Transportation Officials, Washington, DC David T. Matsuda, Deputy Administrator, Maritime Administration, U.S.DOT Victor M. Mendez, Administrator, Federal Highway Administration, U.S.DOT William W. Millar, President, American Public Transportation Association, Washington, DC Robert J. Papp (Adm., U.S. Coast Guard), Commandant, U.S. Coast Guard, U.S. Department of Homeland Security, Washington, DC Cynthia L. Quarterman, Administrator, Pipeline and Hazardous Materials Safety Administration, U.S.DOT Peter M. Rogoff, Administrator, Federal Transit Administration, U.S.DOT David L. Strickland, Administrator, National Highway Traffic Safety Administration, U.S.DOT Joseph C. Szabo, Administrator, Federal Railroad Administration, U.S.DOT Polly Trottenberg, Assistant Secretary for Transportation Policy, U.S.DOT Robert L. Van Antwerp (Lt. Gen., U.S. Army), Chief of Engineers and Commanding General, U.S. Army Corps of Engineers, Washington, DC

*Membership as of July 2010.


ACRP REPORT 40 Airport Curbside and Terminal Area Roadway Operations LEIGHFISHER Burlingame, CA IN ASSOCIATION WITH



WILTEC Pasadena, CA

Subscriber Categories

Aviation • Design • Operations and Traffic Management

Research sponsored by the Federal Aviation Administration




Airports are vital national resources. They serve a key role in transportation of people and goods and in regional, national, and international commerce. They are where the nation’s aviation system connects with other modes of transportation and where federal responsibility for managing and regulating air traffic operations intersects with the role of state and local governments that own and operate most airports. Research is necessary to solve common operating problems, to adapt appropriate new technologies from other industries, and to introduce innovations into the airport industry. The Airport Cooperative Research Program (ACRP) serves as one of the principal means by which the airport industry can develop innovative near-term solutions to meet demands placed on it. The need for ACRP was identified in TRB Special Report 272: Airport Research Needs: Cooperative Solutions in 2003, based on a study sponsored by the Federal Aviation Administration (FAA). The ACRP carries out applied research on problems that are shared by airport operating agencies and are not being adequately addressed by existing federal research programs. It is modeled after the successful National Cooperative Highway Research Program and Transit Cooperative Research Program. The ACRP undertakes research and other technical activities in a variety of airport subject areas, including design, construction, maintenance, operations, safety, security, policy, planning, human resources, and administration. The ACRP provides a forum where airport operators can cooperatively address common operational problems. The ACRP was authorized in December 2003 as part of the Vision 100-Century of Aviation Reauthorization Act. The primary participants in the ACRP are (1) an independent governing board, the ACRP Oversight Committee (AOC), appointed by the Secretary of the U.S. Department of Transportation with representation from airport operating agencies, other stakeholders, and relevant industry organizations such as the Airports Council International-North America (ACI-NA), the American Association of Airport Executives (AAAE), the National Association of State Aviation Officials (NASAO), and the Air Transport Association (ATA) as vital links to the airport community; (2) the TRB as program manager and secretariat for the governing board; and (3) the FAA as program sponsor. In October 2005, the FAA executed a contract with the National Academies formally initiating the program. The ACRP benefits from the cooperation and participation of airport professionals, air carriers, shippers, state and local government officials, equipment and service suppliers, other airport users, and research organizations. Each of these participants has different interests and responsibilities, and each is an integral part of this cooperative research effort. Research problem statements for the ACRP are solicited periodically but may be submitted to the TRB by anyone at any time. It is the responsibility of the AOC to formulate the research program by identifying the highest priority projects and defining funding levels and expected products. Once selected, each ACRP project is assigned to an expert panel, appointed by the TRB. Panels include experienced practitioners and research specialists; heavy emphasis is placed on including airport professionals, the intended users of the research products. The panels prepare project statements (requests for proposals), select contractors, and provide technical guidance and counsel throughout the life of the project. The process for developing research problem statements and selecting research agencies has been used by TRB in managing cooperative research programs since 1962. As in other TRB activities, ACRP project panels serve voluntarily without compensation. Primary emphasis is placed on disseminating ACRP results to the intended end-users of the research: airport operating agencies, service providers, and suppliers. The ACRP produces a series of research reports for use by airport operators, local agencies, the FAA, and other interested parties, and industry associations may arrange for workshops, training aids, field visits, and other activities to ensure that results are implemented by airport-industry practitioners.

Project 07-02 ISSN 1935-9802 ISBN 978-0-309-15512-0 Library of Congress Control Number 2010937921 © 2010 National Academy of Sciences. All rights reserved.

COPYRIGHT INFORMATION Authors herein are responsible for the authenticity of their materials and for obtaining written permissions from publishers or persons who own the copyright to any previously published or copyrighted material used herein. Cooperative Research Programs (CRP) grants permission to reproduce material in this publication for classroom and not-for-profit purposes. Permission is given with the understanding that none of the material will be used to imply TRB or FAA endorsement of a particular product, method, or practice. It is expected that those reproducing the material in this document for educational and not-for-profit uses will give appropriate acknowledgment of the source of any reprinted or reproduced material. For other uses of the material, request permission from CRP.

NOTICE The project that is the subject of this report was a part of the Airport Cooperative Research Program, conducted by the Transportation Research Board with the approval of the Governing Board of the National Research Council. The members of the technical panel selected to monitor this project and to review this report were chosen for their special competencies and with regard for appropriate balance. The report was reviewed by the technical panel and accepted for publication according to procedures established and overseen by the Transportation Research Board and approved by the Governing Board of the National Research Council. The opinions and conclusions expressed or implied in this report are those of the researchers who performed the research and are not necessarily those of the Transportation Research Board, the National Research Council, or the program sponsors. The Transportation Research Board of the National Academies, the National Research Council, and the sponsors of the Airport Cooperative Research Program do not endorse products or manufacturers. Trade or manufacturers’ names appear herein solely because they are considered essential to the object of the report.

Published reports of the

AIRPORT COOPERATIVE RESEARCH PROGRAM are available from: Transportation Research Board Business Office 500 Fifth Street, NW Washington, DC 20001 and can be ordered through the Internet at Printed in the United States of America


CRP STAFF FOR ACRP REPORT 40 Christopher W. Jenks, Director, Cooperative Research Programs Crawford F. Jencks, Deputy Director, Cooperative Research Programs Michael R. Salamone, ACRP Manager B. Ray Derr, Senior Program Officer Emily R. Greenwood, Senior Program Assistant Eileen P. Delaney, Director of Publications Hilary Freer, Senior Editor Doug English, Editor

ACRP PROJECT 07-02 PANEL Field of Design Craig Leiner, Massachusetts Port Authority, East Boston, MA (Chair) Owen P. Curtis, HNTB Corporation, Arlington, VA Nathalie Martel, AECOM, Montreal, QC Scott S. Washburn, University of Florida, Gainesville, FL Kum L. “Dan” Wong, American Planning Association, San Francisco, CA Chris Hugunin, FAA Liaison Richard A. Cunard, TRB Liaison

AUTHOR ACKNOWLEDGMENTS The research discussed in this report was conducted under ACRP Project 07-02, “Airport Curbside and Terminal Area Roadway Operations,” by a research team of recognized experts in airport planning and operations, traffic engineering, and transportation planning. LeighFisher (formerly Jacobs Consultancy) was the prime consultant. Peter B. Mandle, LeighFisher Director, was the Principal Investigator and W. Gavin R. Duncan, LeighFisher Principal Consultant, was the Deputy Principal Investigator. Other contributors from LeighFisher included Andrew Blaisdell, Dan Barton, and Tyler Tate, Consultants; and Mark Nagle, Principal Consultant. Dowling Associates was the primary subconsultant and led the research concerning roadway weaving analyses under the direction of Rick Dowling, President, and Marty Beene, Vice President. Senanu Ashiabor, a Dowling Associates Associate Engineer, also contributed. The focus groups of airline passengers were conducted by Jennifer D. Franz, President of JD Franz Research, Inc. The traffic surveys at Oakland, San Francisco, and Washington Dulles international airports were conducted by WILTEC under the direction of Moses Wilson, President. Faith Oiwa of LeighFisher coordinated the internal production and word processing of this report. Debra L. Lubin served as the technical editor. The research team would like to express its gratitude to the members of the Project Panel for their support and insightful comments and advice throughout this research project. The research team would also like to thank the many airport staff members and consultants who took the time to review interim drafts of the Guide and provide their thoughts and comments. These reviewers included Foster de la Houassaye of Kimley-Horn Associates, Inc., and Joel Marcuson of Jacobs Engineering, both of whom served as subcontractors; John Bergener of the City and County of San Francisco (San Francisco International Airport); Michael Hackett of the Metropolitan Washington Airports Authority (Washington Dulles International and Reagan Washington National airports); Hugh Johnson of the Port of Oakland (Oakland International Airport); Keith B. Wilschetz of the San Diego County Regional Airport Authority (San Diego International Airport); James W. Green of AECOM; and M. Allen Hoffman of Ricondo & Associates, Inc.


By B. Ray Derr Staff Officer Transportation Research Board

This guide presents a cohesive approach to analyzing traffic operations on airport curbside and terminal area roadways. The guide describes operational performance measures and reviews methods of estimating those performance measures. A quick analysis tool for curbside operations and low-speed roadway weaving areas is packaged with this guide. Techniques for estimating traffic volumes are presented as well as common ways of addressing operational problems. The guide should be useful to airport landside operators, transportation planners, and consultants analyzing airport curbside and terminal area roadway operations.

Efficient and safe roadway operations are critical to an airport's success. Key elements of an airport’s roadway operations are the curbside—where travelers and their baggage enter and exit the terminal—and the terminal area roadways that provide private and commercial vehicles access to the curbside as well as to other destinations such as parking. Travelers expect safe and efficient roadway operations even as volumes increase, but the design and capacity of the curbside are often constrained by the terminal building and the proximity of on-airport landside infrastructure. For more than 60 years, the Transportation Research Board’s Highway Capacity Manual (HCM) has been the authoritative reference for estimating the capacity and determining the level of service for transportation facilities, including intersections and roadways. Over the decades, the HCM has grown to address additional types of facilities and better meet the needs of analysts. Although it now includes transit, bicycle, and pedestrian facilities, it does not address the unique challenges posed by airport transportation facilities. Some of these challenges are related to the tight geometrics due to limited space in the terminal area while others are due to the differences in traffic composition and traveler expectations. In this project, LeighFisher took the first step toward creating analysis guidance comparable to the HCM for airport curbside and terminal area roadways. They surveyed the largest U.S. and Canadian airports to obtain reports from recent landside analyses. They reviewed these reports to identify analysis methods and performance measures of interest, which were then critically reviewed. A conceptual model for analyzing curbside operations and low-speed weaving areas was then developed. Field data were collected for the development of a macroscopic queuing model for curbside operations and low-speed weaving areas. The research team then wrote the guide and validated it with the project panel and staff at two airports. The project panel believes that the guide will be practical and useful for conducting roadway analyses. The guide establishes a baseline for analysis based on the current state of the art but future additional research and experienced analysts will develop better analysis methods, much as they have for the HCM. These improvements can be incorporated into the analysis approach in the future.


1 1 1 1

3 3 4 7 13 14

16 16 17 28

30 30 30 32 39 40


Chapter 1 Purpose, Methodology, and Organization of this Guide Purpose of the Guide Methodology Organization of the Guide

Chapter 2 Framework for Analysis of Airport Roadways and Curbsides Users of Airport Roadways Types of Airport Roadways Operating Characteristics of Airport Terminal Area Roadways Overview of Analytical Framework Hierarchy Overview of Capacity and Level-of-Service Concepts

Chapter 3 Estimating Airport Roadway Traffic Volumes Establishing Existing Airport Roadway Traffic Volumes Estimating Future Airport Roadway Traffic Volumes—Traditional Four-Step Approach Estimating Future Airport Roadway Traffic Volumes—Alternative Approach

Chapter 4 Analyzing Airport Terminal Area Roadways Level-of-Service Definitions for Airport Terminal Area Roadways Quick-Estimation Methods for Analyzing Airport Roadway Operations Macroscopic Method for Analyzing Airport Roadway Weaving Areas Use of Microsimulation Methods Other Performance Measures

Chapter 5 Evaluating Airport Curbside Operations

41 42 43 45 50

Performance Measures Level-of-Service Definitions for Airport Curbside Roadways Estimating Airport Curbside Roadway Traffic Volumes Estimating Airport Curbside Roadway Capacity and Level of Service Analytical Framework Hierarchy for Airport Curbside Roadways


Chapter 6 Improving Airport Curbside and Terminal Area Roadway Operations

57 60 63 64

Typical Terminal Area Roadway Problems Potential Terminal Area Roadway Improvement Measures Typical Curbside Roadway Problems Potential Curbside Roadway Improvement Measures

Note: Many of the photographs, figures, and tables in this report have been converted from color to grayscale for printing. The electronic version of the report (posted on the Web at retains the color versions.

70 71

Appendices Appendix A Glossary



Purpose, Methodology, and Organization of this Guide ACRP Report 40: Airport Curbside and Terminal Area Roadway Operations (the Guide) is intended to assist airport operators and others in analyzing airport terminal area roadway and curbside operations. The Guide presents guidelines for estimating airport roadway requirements and capacities, recommended performance measures, valid and useful analytical methods, and potential measures to improve terminal area and curbside roadway operations.

Purpose of the Guide This Guide is intended for use by three primary user groups. The first user group consists of airport operators, including the staff responsible for planning, design, and day-to-day operations of airport terminal area and curbside roadways. The second user group includes city, regional, and state transportation planners who may not be familiar with airport roadway operations. The third user group consists of airport consultants who are engaged to conduct planning, environmental, design, and other projects on behalf of airport operators and other sponsors. Some users may have significant experience with airports or aviation, but little familiarity with traffic engineering or transportation planning principles. Other users may have experience in traffic engineering and transportation planning, but little knowledge of airport operations. This Guide is intended to assist both groups. For users unfamiliar with airports, the Guide describes the unique operating characteristics of airport terminal area roadways and curbside areas, and how their operations differ from those of urban streets and regional highways. The Guide presents methods for estimating existing and future airport roadway requirements and alternative methods for analyzing operations on airport roadways.

Methodology The Guide was prepared under the direction and guidance of the project panel. The Guide reflects information gathered

through an extensive literature review and the performance of more than a dozen focus groups of airline passengers, airport landside operators, and the drivers of commercial ground transportation vehicles serving airports. The definitions of curbside and weaving area levels of service included in this Guide reflect the input and comments received during the focus group sessions. Traffic volumes gathered during a week-long survey period at Oakland and Washington Dulles International Airports were used to develop and validate new macroscopic models for analyzing and evaluating airport curbside roadway operations and low-speed weaving, as described in this Guide. The draft Guide and the macroscopic models were reviewed by representatives of these two airports and other airports.

Organization of the Guide This Guide consists of six chapters and seven appendices (see for Appendices B through G). Chapters 2 through 6 are summarized below: • Chapter 2, Framework for Analysis of Airport Roadways

and Curbsides, describes the types of vehicles and roadways typically found on airports and their unique operating characteristics. An overview is provided of (a) the hierarchy of analytical methods—quick-estimation methods, macroscopic models, and microsimulation methods—presented in Chapters 4 and 5 of this Guide—and (b) the concepts of capacity and level of service, as presented in the 2000 Highway Capacity Manual (HCM). • Chapter 3, Estimating Airport Roadway Traffic Volumes, describes the data required to analyze existing roadway traffic operations and ways to gather these data. Two alternative methods for estimating future roadway requirements are presented, along with the challenges inherent in each method.

2 • Chapter 4, Analyzing Airport Terminal Area Roadways,

presents definitions of levels of service for airport terminal area roadway operations and a hierarchy of analytical methods for analyzing terminal area roadway operations, including low-speed weaving areas, capacities, and levels of service. • Chapter 5, Evaluating Airport Curbside Operations, presents definitions of levels of service for airport curbside roadway operations and a hierarchy of analytical methods for quickly estimating curbside roadway capacities and levels of service, including a macroscopic model—the Quick Analysis Tool for Airport Roadways (QATAR) developed during this research project. • Chapter 6, Improving Airport Curbside and Terminal Area Roadway Operations, presents examples of commonly occurring airport curbside and roadway operational problems, describes potential improvement measures, and overviews steps for analyzing and evaluating airport roadway improvements.

The Guide also contains seven appendices as follows: • Appendix A: Glossary of technical terms used in the Guide. • Appendix B: Bibliography of resource documents reviewed

for this research project. • Appendix C: Summary of Terminal Area Roadway Traffic

Volume Surveys conducted as part of this research. • Appendix D: Summary of Curbside Roadway Traffic Char-

acteristic Surveys conducted as part of this research. • Appendix E: Summary of Focus Group Surveys of airline

passengers, airport landside operators, and the drivers of commercial ground transportation vehicles serving airports conducted as part of this research • Appendix F: A Reproduction of Portions of TRB Circular 212 presenting the Critical Movement Analysis for signalized intersections and the application of this analysis method • Appendix G: Overview of QATAR Curbside Analysis Methodology presenting the use and application of this model as well as the spreadsheet model itself.



Framework for Analysis of Airport Roadways and Curbsides On-airport roadways are a unique class of roadways. Unfamiliar drivers mix with significant numbers of professionally driven large vans and buses; entrances and exits at major airports operate at near-freeway conditions, while curbside roadways operate at much slower speeds, as drivers attempt to maneuver into and out of curbside spaces. Double and triple parking and jaywalking frequently occur on curbside roadways despite the visible presence of traffic enforcement officers. Standard highway capacity analysis procedures can address some aspects of these conditions, but not the full spectrum of operating conditions that exist on airport terminal area and curbside roadways. The various users and types of airport roadways and curbsides, and their unique operating characteristics are described in this chapter. Overviews of (1) the hierarchy of methods for analyzing airport roadway and curbside operations and (2) roadway capacity and level-of-service concepts also are presented.

Users of Airport Roadways Airport roadways provide access to and from the multiple land uses on an airport. These roadways serve vehicles transporting airline passengers and visitors (in this Guide, “visitors” refers to meeters, greeters, and well-wishers accompanying or greeting airline passengers), employees of the airlines and other airport tenants, air cargo and mail, as well as vehicles used for the delivery of goods and services, maintenance, to support airport operations or construction, and other purposes. A multitude of vehicle types use airport roadways. They include private vehicles, rental cars, on-demand and prereserved taxicabs, prearranged and on-demand limousines or Town Cars, door-to-door vans, courtesy vehicles, charter buses, scheduled buses, and service and delivery vehicles. Each vehicle/user type has its own special characteristics and affects airport roadway operations differently, as described below.

1. Private vehicles. Privately owned and operated vehicles consist of automobiles, vans, pickup trucks, and motorcycles used to transport airline passengers, visitors, and employees of the airport operator, airlines, and other airport tenants. Motorists transporting airline passengers in private vehicles may use the curbside areas, parking facilities (including cell phone lots), or both. 2. Rental cars. Rental vehicles, including automobiles and vans, used to transport airline passengers or visitors, are rented by passengers or visitors from rental car companies doing business on or near the airport for the duration of the passengers’ or visitors’ trips. Rental car customers may use the curbside areas, rental car ready and return areas, or both. 3. On-demand taxicabs. Taxicabs provide door-to-door service without prior reservations, which is typically exclusive (i.e., for a single party) and provided in vehicles capable of transporting five passengers plus their baggage. These vehicles are typically licensed and regulated by a municipal taxicab authority. Typically, on-demand taxicabs wait for deplaning passengers at a taxicab stand (or in a taxicab queue) at the curbside area next to the baggage claim area. At large airports, taxicabs may wait in a remotely located taxicab holding or staging area until they are dispatched to the curbside taxicab stand in response to customer demand. 4. Pre-reserved taxicabs. Pre-reserved taxicab service is exclusive, door-to-door transportation provided in vehicles capable of transporting up to five customers plus their baggage. Rather than being provided on demand, as traditional taxicab service, pre-reserved taxicabs are provided in response to prior reservations made by airline passengers seeking to be picked up by a specific company or driver, including suburban taxicabs not regulated by the municipal taxicab authority. Passengers with special needs, such as those with skis, golf clubs, large amounts of






baggage, disabilities, or passengers using a credit card to pay the fare, may request service by specific vehicles or companies. Typically, pre-reserved taxicabs or taxicabs requested specially are not allowed to wait at the curbside taxicab stand, but are assigned curb space at nearby or alternative locations. Prearranged limousines. Prearranged limousine service is exclusive door-to-door transportation provided in luxury vehicles capable of transporting a single party consisting of up to five customers (or more in stretch limousines) regulated by a local or state agency. Generally, limousine service is only available to customers who have made prior reservations (i.e., prearranged) and are greeted (or picked up) by a driver having a waybill or other evidence of the reservations. Some airport operators allow limousine drivers to park at the curbside and wait for customers; others require that the drivers park in a parking lot or other designated zone and accompany their customers from the terminal to the parking area. On-demand limousines or Town Cars. Privately operated on-demand door-to-door transportation is also provided by exclusive luxury vehicles or “Town Cars” capable of transporting up to five passengers and their baggage. These services are similar to on-demand taxicab services, but are provided in luxury vehicles with higher fares than those charged for taxicab services. Door-to-door vans. Door-to-door or shared-ride van services are typically provided in vans capable of transporting 8 to 10 passengers and their baggage. The service is available on both an on-demand and prearranged basis. Passengers, who may share the vehicle with other passengers, are provided door-to-door service between the airport and their homes, offices, or other locations, but may encounter several (typically four or fewer) en route stops. Typically, door-to-door vans wait for deplaning passengers at the curbside next to the baggage claim area. Similar to taxicabs, vans may be required to wait in hold or staging areas until they are dispatched to the curbside in response to customer demand. Courtesy vehicles. Door-to-door courtesy vehicle service is shared-ride transportation provided by the operators of hotels, motels, rental car companies, parking lot operators (both privately owned and airport operated parking lots), and others solely for their customers. Typically, no fare is charged because the cost of the transportation is considered part of, or incidental to, the primary service being provided. Courtesy vehicle service is provided in shuttle vehicles, including 8- to 12-passenger vans (e.g., those operated by small motels), minibuses, and full-size buses (e.g., those operated by rental car companies at large airports). Typically, courtesy vehicles pick up customers at

designated curbside areas that have been reserved or allocated for their use. 9. Charter buses. Charter bus service (also referred to as tour bus or cruise ship bus service) is door-to-door service provided to a party (or group of passengers) that has made prior reservations or arrangements for the service. Charter bus and van service is provided using over-the-road coaches, full-size buses, minibuses, and vans seating more than five passengers. Since charter bus service is sporadically provided at most airports, curb space (or other passenger pickup areas) is either not allocated for charter buses or is shared with other transportation modes. Exceptions include airports serving large volumes of charter or cruise ship passengers on a regular basis. Typically, charter buses are required to wait in a remotely located hold area until the arrival or assembly of the party being provided the service. 10. Scheduled buses. Scheduled buses provide shared-ride service at established stops along a fixed route and operate on a scheduled basis. Typically, scheduled buses are operated by a public agency and make multiple stops along a designated route, but in some communities express or semi-express service is operated by a private operator or public agency. The location and amount of curb space allocated to scheduled buses depends on the volume of such service and the policy of the airport operator. 11. Service and delivery vehicles. Service vehicles include a wide range of trucks, vans, and semi-trailers, and other delivery vehicles used to transport goods, air cargo and mail, contractors, and refuse to and from the airport. Generally, deliveries are made at designated loading docks or warehouses, not at the terminal curbside. However, the pickup and drop-off locations for airline-operated small package delivery services, which are provided by small vans and light trucks, are at the terminal curbside at some airports.

Types of Airport Roadways Although the airport passenger terminal building and surrounding area (the terminal area) is the most prominent location on an airport, depending on the size, type, and distribution of airport land uses, less than half of all traffic on an airport may be associated with passengers and visitors proceeding to/from the terminal area; the remaining traffic is generated by nonairline passenger activities, including employees. Regardless of airport size, the variety of land uses found on an airport requires a network of roadways to provide for inbound and outbound traffic, and the internal circulation of traffic between land uses. The roadway network consists of the types of roadways depicted on Figure 2-1.


Figure 2-1. Hierarchy of airport roadway classifications.

Access Roadways For purposes of this Guide, airport access roadways are defined as the roadways linking the regional highway and roadway network with the airport terminal and other areas of the airport that attract large volumes of airline passenger-generated traffic, such as parking and rental car facilities. Access roadways provide for the free flow of traffic between the regional network and the passenger terminal building or other major public facilities, and typically have a limited number of decision points (i.e., entrances or exits). At large airports, access roadways are often limited-access roadways with both at-grade intersections and grade-separated interchanges. At smaller airports, access roadways often have at-grade intersections that may be signalized, stop-sign controlled, or have roundabouts (yield-sign controlled).

Curbside Roadways Curbside roadways are one-way roadways located immediately in front of the terminal buildings where vehicles stop to

pick up and drop off airline passengers and their baggage. Curbside roadways typically consist of (1) an inner lane(s) where vehicles stop or stand in a nose-to-tail manner while passengers board and alight, (2) an adjacent maneuvering lane, and (3) one or more through or bypass lanes. Curb space is often allocated or reserved along the inner lane for specific vehicles or classes of vehicles (e.g., taxicabs, shuttle buses, or courtesy vehicles), particularly at the curbside areas serving baggage claim or passenger pickup. As shown on Figure 2-2, depending on the configuration of the adjacent terminal building, curbside roadways may include one, two, or more vertical levels and/or one, two, or more parallel roadways separated by raised medians (often called islands). At airports with dual-level curbsides, the upper level curbside area is at the same level as airline passenger ticketing and check-in facilities inside the terminal and is intended for passenger drop-off. The lower level curbside area is at the same level as the baggage claim area and is reserved for passenger pickup. At airports with multiple terminals where one of the parallel roadways serves as a bypass roadway, cut-through


Figure 2-2. Typical airport curbside configuration.

roadways may be provided to allow vehicles to circulate between the inner and outer parallel roadways (and curbside roads).

Circulation Roadways Circulation roadways generally serve a lower volume of traffic and are less direct than the roadways served by access road-

ways. Circulation roadways often provide a variety of paths for the movement of vehicles between the terminals, parking, and rental car facilities. Examples include return-to-terminal roadways that allow motorists to proceed to parking after having dropped off airline passengers (or proceed from parking to the terminals) and allow courtesy or other vehicles to return to the terminal (e.g., after having dropped off enplaning airline passengers and returning to pick up deplaning passengers on a


different curbside roadway). Compared to access roadways, circulation roadways typically operate at lower speeds and allow for multiple decision points. The above roadways—access roadways, curbside roadways, and circulation roadways—are considered “curbside and terminal area” roadways and are the focus of this Guide. Other airport roads include service and access roads, as described below.

Service Roads Service roads link the airport access roadways with onairport hotels, employee parking areas, and employment centers (e.g., aircraft maintenance facilities or hangars), air cargo/air freight buildings and overnight parcel delivery services, loading docks/trash pickup areas, post offices, fixedbase operators (FBOs) or general aviation areas, airport maintenance buildings and garages, military bases, and other nonsecure portions of the airport that generate little airline passenger traffic. The traffic generated by these land uses differs from that generated by the passenger terminal building in several respects. First, the traffic on service roads includes a higher proportion of trucks, semi-trailers, and other heavy vehicles than the traffic on curbside and terminal area roadways, which rarely serve trucks or delivery vehicles. Second, most drivers on the service roads (e.g., employees and drivers of cargo vehicles) use these roads frequently and are familiar with the roads and their destinations, unlike drivers using the curbside and terminal area roadways. For purposes of operational analyses, the service roads are similar to those found in an industrial park. Typically, they consist of two- to four-lane roads with generous provision for the turning paths of large trucks and semi-trailers and for entering and exiting vehicles, including separate or exclusive turning lanes.

Airfield Roads A separate network of roads located within the aircraft operating area or the airfield is used by ground service equipment, including vehicles servicing aircraft, towing aircraft, or towing baggage carts and vehicles used for runway maintenance or emergency response. Often these vehicles are not licensed to operate on public streets. Only drivers with airfield licenses are permitted to operate vehicles with aerodrome permits in secure or restricted areas. The design and operation of these roads is addressed in guidelines issued by the FAA Series 150 Advisory Circulars The remainder of this Guide addresses curbside and terminal area roadways only.

Operating Characteristics of Airport Terminal Area Roadways The operating characteristics of airport terminal area roadways differ from those of other public roads. This section describes the distinguishing operating characteristics of airport terminal area roadways, weaving sections, and curbside areas.

What Makes Airport Roadway Operations Unique The main differences between the operating characteristics of airport terminal area access and circulation roadways and nonairport roadways include • A high proportion of unfamiliar motorists. Because most

airline passengers fly infrequently (e.g., fewer than four times per year), they (and the drivers who are dropping them off/picking them up) are not familiar with the roadways at their local airport(s), much less the roadways at their destination airport(s). Unlike commuters, who rarely need to refer to roadway signs, airline passengers rely upon signs (or other visual cues) to guide them into and out of an airport and to/from their destinations on the airport. Picking up passengers may be particularly challenging for unfamiliar motorists, who must follow the appropriate signs, be aware of all the traffic and pedestrian activity at the curbside areas, and also be able to identify their party among crowds of other passengers waiting to be picked up. • Large number of complex directional signs. Directional signs on airports often provide more information (i.e., more lines of text) than those on public roadways governed by the Manual of Uniform Traffic Control Devices (published by FHWA) because of the number of terminals, separation of departures and arrivals level roadways, airlines, parking options, and rental car companies that must be provided to motorists (see Figure 2-3). For example, the general policy at U.S. airports is to display the name of every airline serving an airport, even those operating only a few times a week. The signs often include colors, fonts, symbols, and messages not used on other public roadway signs. Because of the number, size, and complexity of these signs, motorists may not see regulatory or warning signs concerning height restrictions, parking rates, security regulations, use restrictions (e.g., authorized vehicles only), and other messages. These signs may result in an overload of information and cause motorists to decelerate while attempting to read the signs. • Stressful conditions. Motorists operating on airport roadways are under more stress than typical motorists. This stress results from the knowledge that minor delays or


Source: LeighFisher.

Figure 2-3. Complex airport roadway signs.

wrong turns may cause a person to arrive too late to check baggage, claim a pre-reserved seat, or greet an arriving passenger, or in an extreme case, miss a flight entirely. Congested airport roadways, closely spaced decision points, and complex signs can add to this stress and discomfort. Factors adding to passenger stress at an airport include the need to connect from a car to a plane, from a car to a

bus, find a parking place, find a passenger (“Where is Aunt Meg?”), find the correct place to drop off or pick up a passenger, locate the taxicab, courtesy vehicle, or city bus stop, and so forth. Passengers realize the importance of making correct decisions in an environment that is more complicated and anxiety-filled than a typical roadway situation so that they do not miss their flights or rides. Each action on an airport is part of a chain of events, any one of which can go wrong and disrupt or delay a vacation, business meeting, or other important event. • High proportion of large vehicles. More than 10 types of ground transportation services operate on airport roadways. The characteristics of each service, the needs of the customers using the services, and the operating characteristics of the vehicles used to provide these services must be considered when developing physical and operational plans for airport curbside and terminal area roadways. Courtesy vehicles, door-to-door vans, scheduled buses, and other large vehicles may represent 10% to 20% of the traffic volume on a terminal area roadway. On a typical public street, less than 10% of the traffic consists of large vehicles. Standard Highway Capacity Manual (HCM) capacity calculation procedures reduce the capacity of a public highway with a high percentage of truck, bus, and other large vehicle traffic to account for the slower acceleration/ deceleration characteristics of these vehicles. However, the use of a capacity adjustment factor may not be necessary on airport terminal area roadways because courtesy vehicles, vans, and buses operating on those roadways do not interfere with the flow of other traffic to the extent that they do on public highways. On airport terminal area roadways, these large vehicles can operate at the range of prevailing speeds typically found on airport roadways (i.e., 25 miles per hour [mph] to 45 mph) and have sufficient power to accelerate and decelerate at rates that are comparable to those of private vehicles—and do so unless they are transporting standing passengers—because most airport roadways are level or have gentle vertical slopes. Additionally, large vehicles such as courtesy vans or shuttle buses may obstruct motorists’ views of wayfinding signs and may interfere with the operation of passing vehicles as they enter or exit curbside areas. • Mix of experienced and inexperienced drivers. Although most private vehicle drivers use an airport infrequently, 20% to 30% of the vehicles on airport roadways are operated by professional drivers who are thoroughly familiar with the on-airport roadways because they use them frequently—perhaps several times each day. This difference contributes to vehicles operating at a range of speeds on the same roadway segment—slow-moving vehicles (e.g., unfamiliar drivers of private vehicles attempting to read signs or complete required turns and maneuvers) and faster vehi-


cles (e.g., taxicabs and limousines operated by professional drivers familiar with the airport roadways and who may ignore posted speed limits). • Recirculating traffic. Traffic officers often require motorists to exit the terminal area if they are not actively loading or unloading passengers, unable to find an empty curbside space, or waiting for an arriving passenger who is not yet at the curbside. Motorists exiting the curbside area may either wait in a cell phone lot until the passenger arrives (which is encouraged by airport operators) or recirculate around the airport and back to the curbside. Table 2-1 indicates the percentage of roadway traffic that recirculates past the terminal more than once.

Weaving is defined as the crossing of two or more traffic streams traveling in the same direction along a length of highway without the aid of a traffic signal or other control device. A weaving maneuver occurs when vehicles enter a roadway segment from one side and exit the segment on the other while other vehicles do the opposite at the same time. The most common example of weaving occurs on freeways where an on-ramp is followed by an off-ramp a short distance later, and those two ramps are connected by an auxiliary lane. The weaving movement occurs when vehicles on the freeway move into the auxiliary lane to exit via the off-

ramp, while vehicles from the on-ramp move from the auxiliary lane onto the freeway. The operation of weaving and merging areas on airport roadways differs from the operation on nonairport roadways primarily because these operations occur at slower speeds on airport roadways than they do on freeways and arterial streets. Weaving analyses generally are conducted for freeways and arterial streets on which vehicles operate at higher speeds than those on most airport roadways. At high speeds, drivers require large gaps between successive vehicles in order to merge into, or weave across, a traffic stream. In the 2000 HCM, it was assumed that a free-flow speed of 35 mph on a weaving section represents level of service (LOS) E (i.e., operations at or near a roadway’s capacity—the HCM chapters on weaving and merging were prepared for freeways). Thus, the metrics used in the HCM to establish satisfactory weaving conditions are not suitable for analysis of airport roadways, which operate at lower speeds than freeways. Chapter 4 of this Guide presents alternative metrics and analysis methods for use on airport roadways. Upon entering an airport, motorists typically encounter a series of exits or turns leading to nonterminal areas (e.g., economy parking, air cargo, general aviation), close-in parking (hourly, daily, or valet) and rental car return (by company), and ticketing/departures vs. baggage claim/arrivals curbside areas. Upon exiting the airport, motorists may encounter a similar series of exits as well as roads leading back to the terminal and alternative regional destinations. Often, the distance between successive decision points is much less than that suggested by highway design standards established for limited access highways because of the relatively short distances available between an airport entrance and the terminal area. Unlike a regional highway where decision points may be separated by a mile or more, successive decision points on an airport may be separated by 500 feet or less. Even though motorists on airport roadways are traveling at speeds (e.g., 35 mph or less) that are slower than those on freeways or arterial roadways, the limited distances between decision points compromise the ability of motorists to recognize, read, and react to roadway guide signs, or do not allow adequate time to complete required merging and weaving maneuvers.

Table 2-1. Percentage of private vehicles recirculating to the arrivals curbside.

What Makes Airport Curbside Operations Unique

These recirculating vehicles contribute to roadway congestion and represent unnecessary traffic volumes. Factors contributing to recirculating roadway traffic include (1) stricter enforcement procedures required by current security regulations, (2) motorists who may not understand the difference between the published flight arrival time and the time when a passenger arrives at the curbside, (3) motorists waiting for passengers whose flights have been delayed, and (4) drivers of commercial vehicles who, in violation of airport regulations, are improperly soliciting customers along the curbside roadway.

What Makes Airport Roadway Weaving Section Operations Unique

Airport Baltimore/Washington International Thurgood Marshall Airport San Francisco International Airport Seattle-Tacoma International Airport Dallas Love Field Reagan Washington National Airport

Recirculating (%) 50% 43% 30% 26% 15%

Source: Based on data provided by Ricondo & Associates, Inc., June 2009.

As noted in Chapter 1, curbside roadways consist of the inner curbside lane(s) where vehicles stop or stand typically in a nose-to-tail arrangement while passengers board and alight, an adjacent maneuvering lane that vehicles may occupy while decelerating or accelerating to enter or exit the curbside lane, and one or more “through” or bypass lanes. The operating characteristics of airport terminal curbsides differ significantly from those of most other roadways because of the interactions


between vehicles maneuvering into and out of curbside spaces and vehicles traveling in the through or bypass lanes. The capacity of a curbside roadway is defined both by the number of vehicles that can be accommodated while stopping to pick up or drop off passengers and the number that can be accommodated while traveling past the curbside in the through lanes. The capacity of the through lanes is restricted by vehicles that are double parked (which is often tolerated on airport curbside roadways) or triple parked. These capacity restrictions can cause traffic delays and the formation of queues that block vehicles trying to maneuver around stopped vehicles or attempting to enter and exit curbside spaces. (Additional information on the operating characteristics of curbside roadways is presented in Chapter 5.) The length (or capacity) of a curbside area must be in balance with the capacity of the through lanes drivers use to enter and exit the curbside area. For example, a mile-long curbside served by only two lanes (one curbside lane and one through lane) would be imbalanced because, even though the curb length could accommodate a large number of vehicles, traffic flow in the single through lane would be delayed every time a vehicle maneuvers into and out of a curbside space or double parks waiting for an empty space. The reverse imbalance would occur with a very short curbside area and multiple through lanes. Other operating characteristics of airport curbside roadways that differ from public roads, as further described in Chapter 5, include the following: • Dwell times. The length of time a vehicle remains stopped

at the curbside area is referred to as “dwell time.” Generally, vehicles transporting a large number of passengers and baggage require a long dwell time. The number of vehicles that can be accommodated along a given curbside length is determined by the size of the vehicles (i.e., the length of the stall each vehicle occupies, including maneuvering space in front of and behind the vehicle) and the amount of time each vehicle remains at the curbside (i.e., the dwell time). Dwell times at a particular airport are affected by enforcement policies (i.e., strict enforcement leads to shorter dwell times) and local driver behavior (e.g., do drivers double park in a way that allows other motorists to easily enter and exit the lane adjacent to the terminal?). Motorists dropping off passengers typically have shorter dwell times than those picking up passengers (unless motorists are prohibited from waiting for the arrival of a deplaning passenger). Thus, since airports generally have equivalent volumes of originating and terminating airline passengers (and associated traffic volumes), the required capacity or length of an arrivals (pickup) curbside area is typically greater than that of the departures (drop-off) curbside area.

• Maneuvering traffic and parking preferences. Unlike

motorists on city streets, motorists parallel parking at airports rarely back into a curbside space. Motorists frequently stop with their vehicles askew to the travel lanes or sidewalk areas rather than maneuvering their vehicles into positions parallel to the curbside. By doing so, they may block or interfere with the flow of traffic in other lanes. Motorists leave space between successive vehicles to assure that they are not blocked and to allow access to the trunk or baggage storage area. Motorists using airport curbside roadways may stop in the second lane even if there is an empty space in the curbside lane to avoid being blocked in by other motorists and to reduce the walking distances of passengers being dropped off (e.g., stop near a desired door or skycap position) or being picked up (e.g., stop at a point near where the person is standing). Thus, motorists frequently stop in the second lane in front of the door serving the desired airline even though there may be an empty curbside space located downstream. The propensity to avoid inner lanes and double park reflects local driver behavior or courtesy. • Capacity of adjacent through lanes. Through-lane capacity is reduced by traffic entering and exiting curbside spaces, high proportions of vehicles double and triple parking, the use of the maneuver lanes, and other factors. As such, the capacity analysis procedures presented in the 2000 HCM are not applicable. Chapter 5 of this Guide presents suggested methods for calculating the capacities of curbside lanes and through lanes at airports. • Uneven distribution of demand. Curbside demand is not uniformly distributed during peak periods, reflecting (1) airline schedules and (2) the uneven distribution of the times passengers arrive at the enplaning curbside prior to their scheduled departures (lead time) or the times passengers arrive at the deplaning curbside after their flights have landed (lag times). Furthermore, stopped vehicles are not uniformly distributed along the length of a curbside area, reflecting motorist preferences for spaces near specific doors and skycap positions and their aversion to spaces near columns or without weather protection, if weather-protected spaces are available. An aerial view of a busy terminal curbside area would show vehicles stopped adjacent to the door(s) serving major airlines. When a new terminal is opened, the airline with the largest market share frequently gets the first choice of ticket counter and baggage claim area locations. Often, this airline selects the most prominent location, which generally is the area nearest the entrance to the curbside area. Thus, curbside demand is often heaviest at the entrance to the curbside area, causing double-parked vehicles and congestion in this area, while downstream areas remain unoccupied.

11 • Allocation of space for commercial vehicles and other

uses. At most airports, curb space is allocated to commercial vehicles on the pickup curbside area. In the allocation of commercial vehicle curb space, multiple factors must be considered in addition to calculated space requirements, such as customer service, operational needs, airport policies, revenues, and perceived or actual competition among ground transportation services. Curb space may also be allocated for disabled parking, police vehicles, airport vehicles, valet parking drop-off/pickup, tow trucks, and other users. Allocation of traffic on inner and outer curbside areas. At airports having inner and outer curbside areas, one curbside area is generally allocated for private vehicles and the other curbside area(s) is (are) allocated for commercial vehicles. It may be difficult to direct private motorists—especially those unfamiliar with the airport—to multiple curbsides (or supplemental curbsides) and, as such, supplemental curbsides are rarely used. Conversely, it is fairly common to direct commercial vehicles to multiple curbside areas. Crosswalk location, frequency, and controls. Crosswalks provide for the safe movement of pedestrians between the terminal building and center island curbside areas or a parking facility located opposite the terminal. The use of crosswalks can be encouraged and jaywalking discouraged by providing numerous crosswalks at convenient (i.e., closely spaced) locations and/or fences or other barriers to pedestrians along the outer island. However, providing multiple crosswalks adversely affects the flow of through traffic. Motorists are often required to stop at more than one crosswalk because traffic controls at the crosswalks (whether traffic officers or signals) are rarely coordinated in such a way as to allow a continuous flow of through vehicles, such as commonly occurs on an urban street. Multiple crosswalks also reduce the available length of curb space. A single crosswalk has less impact on through traffic and available curb length than multiple, unsignalized crosswalks, although multiple crosswalks are more convenient. Curbside lane widths. At most airports, curbside roadway lane widths are the same as those on public streets (e.g., 10 to 12 feet). Recognizing the tendency of drivers to double park, some airport operators have elected to delineate one double-wide (e.g., 20 to 24 feet) curbside lane rather than two adjacent 10- to 12-foot lanes. (See Figure 2-4.) Availability of short-duration parking. Curbside demand can be influenced by the availability and price of conveniently located, short-duration (e.g., hourly) parking. If such parking is readily available and reasonably priced, fewer motorists may choose to use the curbsides. Conversely, the perceived lack or high cost of available short-duration parking spaces can discourage motorists from parking and instead lead to increased curbside demand. Similarly, the

Source: LeighFisher.

Figure 2-4. Double-wide curbside lane at Washington Dulles International Airport.

availability of cell phone or call-and-wait lots can reduce curbside roadway traffic volumes. • Multiterminal airports. Large airports may have multiple terminals, each with separate curbside areas, or continuous curbsides that extend between terminal buildings. Curbside operations at each terminal may differ, reflecting the characteristics of the dominant passenger groups and airlines (e.g., international vs. domestic passengers, or legacy vs. low cost carriers). • Recirculating or bypass traffic. At many airports, there is a significant proportion of nonstopping or bypass traffic on the terminal curbsides. This bypass traffic includes (1) recirculating traffic that, because of police enforcement or other reasons, passes the terminal curbside (particularly the deplaning curbside) more than once, (2) curbside traffic destined for another terminal or adjacent curbside section, which must bypass the curbside in question, and (3) noncurbside traffic traveling past the curbside (e.g., cut-through vehicles, employee vehicles, or airport service or maintenance vehicles). • Nonstandard curbside configurations. Although most airports have linear curbsides where vehicles stop bumper to bumper or nose to tail, a few airports have nonstandard curbside configurations. – Pull-through private vehicle spaces. As shown on Figure 2-5, the curbside areas at some U.S. airports (e.g., Lambert-St. Louis International, Nashville International, and Little Rock National Airports), as well as many overseas, have (or had) pull-through spaces arranged at 45-degree angles that allow motorists to pull through, similar to the way they would at a drive-through window.


Source: LeighFisher.

Source: LeighFisher.

Figure 2-5. Pull-through curbside lanes at Brussels Airport.

Figure 2-7. Pay for curbside use at Paris Charles de Gaulle International Airport.

– Angled commercial vehicle spaces. The commercial vehicle curbside areas at the airports serving Atlanta, Newark, and Orlando, among others, have angled spaces that require vehicles to back up to exit. – Driver-side loading. As shown on Figure 2-6, at a few airports (e.g., Bush Intercontinental Airport/Houston and Mineta San Jose International Airport), the deplaning curbsides are located on the driver’s side of the vehicle, requiring private vehicle passengers to open the door and enter or exit the vehicle on the side away from the terminal building while standing in a traffic lane. Driver-side loading is used at some airports for taxicabs because passengers may enter the cab from either side of the vehicle. – Brief parking zones—pay for curbside use. Some European airports do not provide free curb space, but instead provide parking areas adjacent to the terminals that

motorists can use for a fee. These areas can be configured parallel to the curbside (see Figure 2-7) or in a traditional parking lot adjacent to the terminal building (see Figure 2-8). In Europe, unattended vehicles are permitted in these zones, but in the United States, current security regulations prohibit unattended vehicles at the terminal curbsides. – Supplemental curbsides. Some airports provide supplemental curbsides in or near parking structures or at remotely located sites. Examples of airports with curbside areas within parking structures include those at the airports serving New York (LaGuardia), St. Louis, and Salt Lake City (see Figure 2-9).

Source: LeighFisher.

Source: LeighFisher.

Figure 2-6. Driver-side loading at Mineta San Jose International Airport.

Figure 2-8. Brief parking curbside zone at Munich Airport.


demand. These methods, however, are less than satisfactory for estimating the operating performance of a given roadway or for refining a given design. If information on the actual performance of a given facility or how to refine a particular design is desired, then macroscopic methods (described below) should be used.

Macroscopic Methods

Source: LeighFisher.

Figure 2-9. Supplemental curbside at Salt Lake City International Airport.

The analytical procedures described in this Guide are most relevant for airports with traditional curb spaces because of the differing dwell times and through-lane operations that occur with other configurations.

Overview of Analytical Framework Hierarchy Subsequent chapters of this Guide present alternative methods for analyzing airport roadways, weaving sections, and curbside areas, recognizing the unique characteristics of these facilities. The alternative analysis methods or hierarchy differ in terms of (1) the level of effort or time needed to conduct the analysis, (2) the expected level of accuracy or reliability of the results, and (3) the necessary level of user skill or experience. The three methods—quick-estimation methods, macroscopic methods, and microsimulation methods—are described in the following paragraphs.

Quick-Estimation Methods Quick-estimation methods, as the name suggests, can be used simply and rapidly to produce preliminary analyses of roadway operations (or other facilities). They generally consist of look-up tables, simple formulas based on regression analysis of databases, or rules of thumb, and are based on broad assumptions about the characteristics of the facility being analyzed. As such, they provide a first test of the ability of a roadway or other facility to properly accommodate the estimated requirements (existing or future) or the adequacy of a potential improvement measure. Quick-estimation methods are ideal for quickly sizing a facility. The analyst can easily check which of many possible roadway design options is sufficient to serve the forecast

Macroscopic methods are used to consider the flows of vehicle streams, rather than the flows or operations of individual vehicles. The HCM is an example of a set of macroscopic methods for evaluating roadway operations. As such, these methods approximate the interactions between individual vehicles, the behavior of individual drivers, and detailed characteristics of the roadways (or other facilities). Adjustment factors, typically developed through empirical observations or microsimulation methods, often are used to account for atypical vehicles or driver characteristics, traffic flow constraints, or other operational characteristics. These methods produce results that are considered acceptable, more accurate than quick-estimation methods, and can be used with less training and experience than microsimulation methods. Macroscopic methods can provide reliable estimates of the steady-state performance of a roadway averaged over a given analysis period. They are best for determining the refinements to a proposed design (or existing facility) that would eliminate capacity and congestion problems. These methods are less satisfactory for quantifying facility operations under heavy congestion conditions. Macroscopic methods are generally unsatisfactory for comparing alternative improvements that reduce but do not eliminate congestion. Under heavily congested conditions (hourly demand exceeding capacity), queuing vehicles from one part of the roadway affect both upstream and downstream operations in a manner that cannot be estimated easily using macroscopic methods. Macroscopic methods also cannot be used for unusual facility types or situations for which they were not designed. In those situations, microsimulation methods must be used.

Microsimulation Methods Microsimulation methods consist of the use of sophisticated computer programs to simulate the operation of individual vehicles on simulated roadway networks. Each vehicle is assigned characteristics, such as a destination, performance capabilities, and driver behavior. Each roadway network is defined using characteristics such as number, length, and width of lanes; operating speeds; traffic controls; and pedestrian activity. As each imaginary vehicle travels through the computerized roadway network, various aspects of its


performance can be recorded based on its interaction with other vehicles and traffic controls. These performance statistics can be summarized in many ways, including commonly used performance measures, such as travel time and delays, travel speeds, and queue lengths. Also, some microsimulation models produce a visual display of the simulated roadway operations, which can be helpful when evaluating operations or presenting results. Of the three methods for analyzing airport roadway conditions, microsimulation methods are the most complex and require the most effort and skill on the part of the user, but they also produce the most detailed and reliable results. The use of microsimulation methods is suggested when macroscopic methods do not yield reasonable results, do not provide sufficient detail, or when the conditions being analyzed are outside the ranges addressed by macroscopic methods. Additional information regarding the application of these three analysis methods is presented in subsequent chapters of this Guide.

Overview of Capacity and Level-of-Service Concepts The concepts of capacity and level of service, as presented in the 2000 HCM, are fundamental to analyses of roadway and other transportation facilities and well understood by traffic engineers and transportation planning professionals. This section is intended to provide an overview of these concepts for users not familiar with the 2000 HCM.

Capacity Concept The capacity of a rectangle or a box can be defined easily by its size (i.e., its area or volume) because the maximum amount the object can accommodate is fixed. This is not true with objects that serve as “processors,” such as roadways, ticket counters, or runways. The capacity of a roadway, for example, depends not only on its size (e.g., the number of lanes and other geometric design aspects), but also on the characteristics of the vehicles using the roadway (e.g., their size, performance, spacing, speed, and many other operating characteristics). If all the vehicles on a roadway were identical in size, distance apart, speed, driver characteristics, and other characteristics, then the capacity of the roadway (number of vehicles traversing a point or section during a unit of time) would be expected to be substantially higher than the capacity of the same roadway if it were serving a mix of vehicle sizes, speeds, and driver characteristics. Accordingly, the capacity of a roadway—even roadways with the same number of lanes—varies based both on the characteristics of the roadway (e.g., lane and shoulder widths, vertical grades, intersection and driveway spacing, and traffic

control types) and the characteristics of the vehicles and drivers using the roadway (e.g., the proportion of trucks or heavy vehicles, daily and hourly variations in use, familiarity of the typical drivers with the roadway). With knowledge of the characteristics of a roadway section and the vehicles (and drivers) using the roadway, it is possible to calculate its capacity—the “maximum hourly rate” of vehicles flowing past a point. However, it is not possible or desirable for a roadway to operate at its capacity for sustained periods, because any minor disruption will cause congestion, which results in delays or lengthy queues and undesirable levels of safety and driver comfort. Thus, roadway capacity, while stated in terms of “base” vehicles (e.g., passenger car equivalents) per hour, is sometimes computed for only the peak 15-minute flow rate within that hour. In addition, roadway operations are characterized in terms of level of service and “service flow rate”—the maximum flow rate that can be accommodated while maintaining a designated level of service. Similar to capacity (maximum hourly vehicle flow rates), service flow rates vary according to the characteristics of a roadway section and the vehicles using the roadway.

Level-of-Service Concept Level of service is a qualitative measure of roadway (or other transportation facility) operations. Six levels of service are defined in the 2000 HCM, with LOS A representing the highest (or best) level of service and LOS F representing the lowest (or worst) level of service. The 2000 HCM defines level of service as follows: . . . a quality measure describing operational conditions within a traffic stream, generally in terms of such service measures as speed and travel time, freedom to maneuver, traffic interruptions, and comfort and convenience.

Levels of service are defined in terms of parameters that can be perceived by the users of a transportation facility and that can be measured and predicted. On roadways, each level of service corresponds to a specific maximum flow rate (i.e., the upper limit of the performance measure threshold (or flow rate)) for that level of service. The parameters or measures of effectiveness defining each level of service are (1) the density of the traffic flow (passenger cars per mile per travel lane) for a freeway or other unsignalized multilane roadway and (2) delay (seconds per vehicle) for signalized and unsignalized intersections.

Commonly Used Level-of-Service Definitions for Airport Terminal Area Roadways As noted, the 2000 HCM defines six levels of service, as presented below. (These definitions were taken from the 2000


HCM, but have been modified slightly for the benefit of airport planners and others not familiar with the HCM.) LOS A represents operations where free-flow speeds prevail. The ability of each driver to maneuver within the traffic stream, change lanes, merge, or weave is almost completely unimpeded by other vehicles because of low traffic densities. The effects of transient blockages or incidents (e.g., an accident, vehicle breakdown, or other event that impedes the flow of traffic) are easily absorbed at this level of service. LOS B represents conditions in which free-flow speeds are maintained. The ability of each driver to maneuver within the traffic stream, change lanes, or weave is only slightly restricted by the presence of other vehicles. The general physical and psychological comfort of drivers is still high. The effects of minor incidents and point breakdowns (e.g., a breakdown in traffic flow where traffic enters, leaves, or crosses a roadway) are still easily absorbed. LOS C represents traffic flow with speeds at or near the freeflow speeds of the roadway. Freedom to maneuver within the traffic stream is noticeably restricted (by the presence of other vehicles) and lane changes may require more care and vigilance on the part of the driver because of high traffic densities. Minor blockages or incidents may still be absorbed, but the local deterioration in service will be substantial. Queues may be expected to form behind any significant blockage. On airport roadways, LOS C is generally considered to be the minimum “acceptable” level of service because of the lack of alternative travel paths and the significant negative consequences of travel delays. LOS D represents the level at which speeds begin to decline slightly with increasing flows, and density (on freeways and other roadways with uninterrupted flows) begins to increase somewhat more quickly. Freedom to maneuver within the traffic stream is more noticeably limited (because of the lack of gaps between successive vehicles), and the driver experiences reduced physical and psychological comfort. Even minor blockages or incidents can be expected to quickly create queues because the traffic stream has little space to absorb disruptions.

LOS E represents operations at or near capacity. Operations at this level are volatile because there are virtually no usable gaps in the traffic stream. Vehicles are closely spaced, leaving little room to maneuver (or allow for lane changes or weaving) within the traffic stream. Any disruption of the traffic stream, such as vehicles entering from a ramp or a vehicle changing lanes, can disrupt upstream traffic flows. At capacity, the traffic stream has no ability to absorb even the most minor disruptions, and any incident can be expected to produce a serious breakdown with extensive queuing. Maneuverability within the traffic stream is extremely limited and the level of physical and psychological comfort afforded the driver is poor. LOS F represents breakdowns in vehicular flow. Such conditions generally exist within queues forming behind bottleneck points. Bottlenecks occur as a result of (1) traffic accidents or incidents, (2) typical traffic congestion areas, such as lane drops, weaving segments, or merges, (3) parking maneuvers, or (4) traffic conditions when the projected hourly flow exceeds the estimated capacity of the roadway segment.

Acceptable Levels of Service for Terminal Area Roadways As noted, levels of service are typically used to determine if a roadway can properly accommodate existing or future traffic operations or compare alternative improvement options. On regional freeways and arterials and in densely developed urban areas, LOS D is often considered acceptable because motorists traveling on regional roadway networks can select alternative travel paths should their preferred path be congested. However, on airport roadways, where only a single path is available (and the cost of delay to the traveler is great), LOS C is typically considered to be the minimum acceptable level of service because of the lack of alternative travel paths and the significant negative consequences resulting from travel delays (e.g., passengers missing their flights).



Estimating Airport Roadway Traffic Volumes

This chapter presents methods for estimating existing and future airport roadway requirements. The data required to analyze existing roadway traffic volumes and operations are described, and two alternative methods for estimating future roadway traffic volumes are presented. One method, the traditional four-step approach commonly used by transportation planners, incorporates estimates of the roadway traffic volumes generated by airline passengers, visitors, employees, air cargo handlers, and major airport land uses. This method requires an extensive database for each of these traffic generators. The second method, the growth factor method, yields acceptable, but less precise results, while requiring much less input data. However, this simpler method is less sensitive to changes in future conditions or travel patterns.

Establishing Existing Airport Roadway Traffic Volumes Analyses of existing conditions and estimates of future conditions should be based on observed vehicular activity. Surveys of traffic volumes, roadway operations, and vehicle characteristics are often conducted to support these analyses. Additional information about traffic surveys can be found in the ITE Manual of Traffic Engineering Studies and other references listed in the bibliography provided in Appendix B to this Guide.

Roadway Traffic Volume Survey Methods Roadway traffic volumes can be obtained inexpensively and quickly through surveys compared to a planning and forecasting analysis. Surveys of roadway traffic can be conducted by (1) the public works or traffic engineering department of a municipality or county using automatic traffic recorders (ATRs), (2) consulting firms that specialize in conducting such surveys, or (3) interns, students, or volunteers recruited to manually record traffic volumes on airport roadways. For example, in 2010 a comprehensive 7-day traffic survey that

included installing ATRs at 25 locations typically cost less than $50,000 (or about $1,000 to $2,000 per location) excluding any analyses of the resulting data. If the analysis of roadway operations is to focus on one roadway segment (e.g., a curbside roadway), it may be necessary to record only the traffic volumes on this segment and/or adjacent roadways rather than to conduct a comprehensive survey of all roadways. Similarly, if peak airport traffic periods are known, it may be possible to record the traffic volumes during a 3-hour peak period coinciding with this peak period rather than conduct day-long, 48-hour, or 7-day surveys.

Selecting Survey Dates Ideally, the traffic volume and curbside surveys should be conducted during the peak hours on a typical busy day (ideally during a peak month). Typically, the peak days occur in the months with the largest volumes of airline traffic. At many airports, the busiest days are Mondays and Fridays, but at some airports—especially those serving large volumes of nonbusiness passengers—the busiest days may be Sundays.

Selecting Survey Hours The peak hours for roadway traffic precede the peak hour for originating airline passenger departures and follow the peak hour for terminating airline passenger arrivals. Peakhour traffic volumes can be determined by counting the numbers of vehicles on the roadway by type of vehicle (for curbside surveys), recording the number of vehicles on the roadway during each 15-minute increment, and then either identifying the four consecutive 15-minute increments with the largest traffic volumes or the busiest 15-minute increment. It is suggested that surveys of the departures area (passenger drop-off area) roadways be conducted during the 3 hours prior to and including the 60-minute period with the most departing flights, and that surveys of the arrivals area (passen-


ger pickup area) roadways be conducted during the 3 hours including and after the 60-minute period with the most arriving flights. The 60-minute departures and arrivals flight peaks do not necessarily coincide.

Surveys of Traffic Characteristics and Operational Patterns In addition to surveys of traffic volumes, analyses of airport roadway operations frequently require other surveys to determine the following: • Vehicle mix. In an airport environment, vehicle mix (or

vehicle classification) refers to the portion of the traffic volume accounted for by individual modes, as defined by both the type of service each mode provides (e.g., taxicab, courtesy vehicle, charter bus) and the type of vehicle used (e.g., sedan, passenger van, minibus, full-size bus). These data are required to analyze curbside roadway operations. • Dwell time. This is the amount of time a vehicle spends parked at a curbside lane (or other passenger loading or unloading area). Typically, the dwell time is the length of time between when the driver parks (i.e., the vehicle comes to a complete stop) and when the driver first attempts to rejoin the traffic stream (it does not include any time during which the driver may be ready to depart, but is prevented from doing so by other vehicles). For some analyses, it is also helpful to measure “active” dwell times (i.e., the length of time a vehicle remains at a curbside while actively loading/unloading passengers and their baggage) as opposed to the “total” dwell time, which reflects the time difference between when a vehicle first stops at a curbside until it leaves the curbside. Dwell time data are required to analyze curbside roadway operations. • Queue length. Queue length is the distance, time, or number of vehicles in a line of vehicles waiting to proceed along a roadway in which (1) the flow rate of the front of the queue determines the average speed within the queue and (2) the rate of vehicles arriving in the queue is greater than the rate of vehicles leaving the queue. Queues form when a group of vehicles is delayed because of downstream congestion or bottlenecks. The length of a queue can be measured by observing, at fixed intervals, the length of slow moving or stopped vehicles, and the time of a queue can be measured by observing how long it takes a vehicle to travel from the back to the front of a queue. The number of vehicles in a queue and the duration, or persistence, of the queue also can be determined through observations. These data are used to support evaluations of airport roadway operations. • Travel speeds. Average travel speeds can be measured by recording the time it takes random vehicles to travel a known distance, such as between two fixed objects or points.

Average travel speeds—particularly along a roadway segment having a length of 1,000 feet or more—can be used to support evaluations of airport roadway operations. Measuring instantaneous speeds (also known as spot speeds) is not useful in airport roadway analyses because the speeds of individual vehicles tend to vary significantly on the roadway network. • Other data. In addition to the data listed above, depending on the nature of the traffic operations problem being addressed, data on vehicle mix (i.e., the proportion of private vehicles, taxicabs, limousines, vans, buses, etc., using the roadways), recirculation volumes (i.e., the proportion of vehicles passing the curbside or other location multiple times, typically determined by recording and matching the license plate numbers of passing vehicles), and curbside occupancies (observations or video recordings of curbside use patterns) are sometimes gathered as part of airport roadway operations analyses. Surveys of airline passengers and visitors are commonly used to gather such data as vehicle mode-choice patterns, passenger arrival patterns, passenger regional approach/departure routes, place of origin/ destination, and use of airport parking facilities.

Estimating Future Airport Roadway Traffic Volumes—Traditional Four-Step Approach Developing a comprehensive estimate of future traffic volumes on airport roadways using the traditional four-step approach involves the following: • Trip generation. Estimating the traffic volume generated

by each on-airport land use during the future airportwide peak hour(s) as well as the peak hour(s) of activity for each land use. • Trip distribution. Determining the points where trips generated by each airport land use enter the airport roadway network. • Mode-choice analysis. Analyzing the travel mode choice patterns of passengers and employees. • Trip assignment. Assigning the estimated traffic volumes to the on-airport and regional roadway networks. In regional planning, the third step—mode-choice analysis— is conducted using sophisticated travel demand forecasting models. These models are used to estimate future mode-choice patterns or changes in existing patterns caused by the introduction of new travel modes (e.g., rail service) or changes in travel time or travel cost. Such models are rarely required in an airport setting. It would be appropriate to include mode-choice analysis during the analyses of airport roadways if a significant change in the existing travel modes were anticipated (e.g., new


scheduled public bus or rail service or expansion of existing service) and if this service were expected to attract significant numbers of airline passengers or employees who currently travel by private vehicles. The three steps applicable to airport roadway operations, as well as challenges to using this approach, are described below.

Estimating Traffic Volumes (Trip Generation) The key generators of airport roadway traffic are airline passengers and accompanying visitors, employees working at the airport, air cargo and airmail services, airlines, in-terminal concessionaires, and other building tenants plus airport tenants with service or delivery needs. At most airports, the data required to estimate the volume of traffic generated by airline passengers are more readily available than comparable data for employees, air cargo, or service and delivery vehicles. Reliable statistics on existing monthly and annual volumes of airline passengers and air cargo tonnage and forecasts of airline passengers and air cargo tonnage are available for all commercial-service airports. However, as described in greater detail in subsequent paragraphs, most airport operators have limited-to-no data available on the number of employees working at their airports, or the types of air cargo shipments (e.g., overnight deliveries, small parcels, international, or other types of freight). As a result, forecasts of traffic generated by airline passengers are often developed in substantially more detail than forecasts of traffic generated by employees, air cargo, or services and deliveries. However, traffic generated by airline passengers may represent less than half of the total (daily) vehicular traffic generated at an airport. Traffic Generated by Airline Passengers Estimating the volume of traffic generated by airline passengers requires the following inputs. Number of originating and terminating airline passengers. Roadway traffic operations are analyzed considering the peak-hour volume (i.e., the traffic volume occurring during the busiest 60 consecutive minutes). Analyses of airport roadway traffic begin with the hourly numbers of originating and terminating airline passengers (or preferably the numbers occurring in 15-minute increments). Originating and terminating airline passenger numbers (rather than enplaned and deplaned passenger numbers) are used to generate traffic volumes because these volumes exclude those passengers transferring between flights. Analyses of hour-by-hour airline passenger numbers indicate when the largest numbers of originating passengers, terminating passengers, and total passengers (originating plus

terminating) arrive at, or depart from, the airport. Separate analyses of these three peak periods (originating, terminating, and total) are required because peak periods of demand on some roadway segments coincide with the originating passenger peak periods (e.g., the departures curbside area), and some coincide with the terminating passenger peak periods (e.g., the arrivals curbside area). The total peak period traffic volume may not coincide with the peak period of either the originating or terminating passengers, but may instead reflect the busiest overall period at the airport (e.g., the hour with the largest traffic volumes on the airport entry and exit roadways). At airports with significant numbers of connecting passengers, the peak hours of airline passenger activity may not correlate with the peak hour of roadway traffic volumes. For airports with multiple terminals or multiple large concourses, it may be necessary to gather these hourly data for each terminal or each concourse. Existing originating and terminating airline passenger numbers are available through the Origin-Destination Survey of Airline Passenger Traffic, Domestic, an online database published by the FAA, which is based on a 10% sample of all airline tickets collected by U.S. airlines. Since foreign flag airlines are not required to participate in this ticket sample, the published originating-terminating airline passenger data may underreport passenger numbers at major international gateway airports. Future peak-hour airline passenger numbers are a function of the future flight schedules of each airline, the anticipated size of aircraft operated (i.e., number of seats), and anticipated passenger load factors. Forecasts of airline passengers can be obtained from recent airport master plans, the FAA Terminal Area Forecast (TAF) (see, and other sources. Master plans may present forecasts of annual or daily airline passenger numbers, as determined using an average day of the peak month or standard busy day rate. Such forecasts may be based on the assumption (particularly at small and medium commercial-service airports) that the existing relationship between peak hour and daily airline passenger numbers will remain constant through the forecast period unless a significant change in airline operations is expected. Passenger characteristics. When possible, it is helpful to disaggregate the numbers of originating and terminating airline passengers by trip purpose and place of residency rather than just considering the total passenger numbers because airline passenger travel patterns (e.g., vehicle occupancies, circulation, and mode-choice patterns) are a function of their trip purpose (business vs. nonbusiness), place of residence (local residents vs. nonresidents), and type of flight (shorthaul domestic, long-haul, transborder, overseas, or other). Typically, these data are obtained from surveys of airline


passengers or from data at peer airports. For example, resident travelers are more likely to use private vehicles and park for the duration of their trips, while nonresidents are more likely to travel to the airport in rental cars or hotel/motel courtesy vehicles and not use parking facilities. Lead and lag times. Airline passenger numbers are reported by the airlines according to the time aircraft are scheduled to depart (push away from the gate), and arrive (touch down). Since these times do not coincide with the times motorists enter and exit airport roadways, to analyze airport roadway traffic operations it is necessary to adjust these times to reflect how much time passengers arrive at the airport in advance of their scheduled flight departure times (lead time) and depart from the airport after their scheduled flight arrival times (lag time). International passengers typically have longer lead and lag times than domestic passengers (because of the 2-hour advance check-in required by most airlines and time required for immigration and customs processing), and leisure travelers typically have longer lead and lag times than business travelers (because they are more likely to have checked baggage). Typically, these data are obtained from surveys of airline passengers or from data at peer airports. Lead time data may be aggregated to form a representative distribution (some-

times referred to as an earliness distribution). Similarly, a representative distribution of lag times is sometimes referred to as a lateness distribution. Travel mode choices. To convert person trips into vehicle trips, it is necessary to first determine the travel modes used by airline passengers (or the percentage of passengers using each available travel mode). Regional transportation planning often considers just two travel modes—private vehicles and public transit—whereas airport roadway planning requires consideration of taxicabs, limousines, courtesy vehicles, rental cars, scheduled buses, and other travel modes. As noted, travel modes are a function of trip purpose and place of residency. Airports serving a large proportion of leisure passengers have distinctly different travel-mode-choice patterns than those serving business markets. However, at most U.S. airports, 70% to 80% of all airline passengers arrive and depart in private vehicles or rental cars. Typically, fewer than 5% to 10% of all passengers use public transportation (e.g., scheduled buses or trains, or door-to-door shared ride vans). The remaining passengers typically use taxicabs, courtesy vehicles serving hotels/motels, parking facilities, rental cars, or transportation services that require prior reservations (e.g., limousines, charter or tour buses/vans). Table 3-1 presents the

Table 3-1. Typical vehicle mode choice and occupancies at selected airports— originating airline passengers.

Los Angeles (a) Private Vehicles Curbside Short-term parking Long-term parking Off-airport parking (e) Subtotal (private vehicles) Rental cars Subtotal Commercial Vehicles Taxicabs Limousines Door-to-door shuttles Hotel/motel courtesy vehicles Public transit Charter/other bus Subtotal (commercial vehicles) Total

42.4% 4.4

San Diego (b)

54.8% 11.4 66.2%

25.5% 17.0 2.5 10.0 55.0% 19.1 74.1%

9.3% 2.0 10.0 5.1 4.1 3.0 33.5% 100.0%

7.3% 1.3 9.5 5.8 1.0 1.0 25.9% 100.0%


Tampa (c) 36.3% 19.5 55.9% 36.9 92.8% 2.3% -3.3 0.3 1.4 7.3% 100.0%

Salt Lake City (d)

Typical vehicle occupancy (number of people)

27.0% 8.5 7.0 4.5 47.0% 35.0 82.0%

1.2 1.3 1.3 1.3

1.5% 2.0 2.0 10.5 0.5 1.5 18.0% 100.0%

1.5 1.5 4.0 2.6 5.0 15.0


(a) Applied Management and Planning Group, 2006 Air Passenger Survey: Final Report. Los Angeles International Airport, December 2007 (b) Jacobs Consultancy, Interim Report 1: San Diego County Regional Airport Authority. Destination Lindbergh, December 2008. (c) (d) HNTB, Landside Report, Salt Lake City International Airport, December 2002. (e) Passengers typically arrive at the curbside in courtesy vehicles.

Source: LeighFisher, July 2009, based on the documents noted above.


mode-choice patterns for typical large-hub airports. These data were obtained from recent studies prepared for Los Angeles, Salt Lake City, San Diego, and Tampa International Airports. Using the format shown in Table 3-1, some airline passengers are counted twice (e.g., a private vehicle driver who parks in an economy lot and rides a courtesy vehicle or a rental car customer who also uses a courtesy vehicle). Vehicle occupancies. Vehicle occupancies (the number of passengers per vehicle) are used to translate or convert “person trips” by travel mode into vehicle trips. When analyzing airport roadways, vehicle occupancies represent the number of airline passengers in each vehicle (i.e., excluding visitors accompanying airline passengers or the drivers of commercial vehicles). Typically, these data are obtained from surveys of airline passengers (for single-occupancy vehicles, such as private vehicles, taxicabs, and limousines) or from visual observations for multiparty vehicles, such as courtesy vehicles, buses, and vans. The average occupancy of private vehicles operating on airports is higher than the average occupancy of private vehicles operating on public streets (particularly during commute hours) because vehicles on airports are typically transporting a group of airline passengers rather than just a single occupant. On-airport traffic circulation patterns. The locations on an airport where motorists begin or end their trips and the paths they follow vary according to their choice of travel mode (and parking facilities), and the on-airport roadway network configuration. Airline passengers follow numerous travel paths on an airport. For example, a private vehicle driver may enter an airport and then do one or more of the following:

parked for the trip duration), drive back to the terminal to pick up passengers, and then exit the airport (e.g., a longterm parking patron). Similarly, rental car customers may go to the curbside area before they drop off rental cars or after they pick up rental cars. Commercial vehicle drivers may drop off customers, wait in a holding area, and then recirculate back to the terminal to pick up additional customers. Table 3-2 presents the travel paths and proportion of airline passengers using these paths for a typical large-hub airport. Medium- and small-hub airports have similar patterns, but at these airports there may be greater use of private vehicles and less use of taxicabs, limousines, courtesy vehicles, and public transit vehicles. Again, these data are typically obtained from surveys of airline passengers. Peak-hour factors. Airport roadway traffic is not uniformly distributed over a typical peak hour or other peak period. At small airports in particular, much larger volumes of traffic may occur during one 15-minute period than during the preceding or subsequent 15-minute period. Peak-hour (adjustment) factors are used to translate nonuniform flows into equivalent hourly flows to allow for the analyses of roadways exhibiting such nonuniform peaks. (This translation is required because roadway capacities are defined and analyses of roadway operations are performed using vehicle volume per hour.) These peak-hour factors can be determined from airport roadway traffic surveys or indirectly from analyses of airline schedules. Traffic volumes generated by airline passengers can be estimated by the following: • Multiplying the number of originating (or terminating)

• Go directly to the enplaning (or deplaning) curbside area

• •

and then immediately exit the airport (e.g., a motorist dropping off an airline passenger who does not park), or recirculate and return to the curbside (e.g., a motorist attempting to pick up a passenger and who was not allowed to remain stopped at the curbside). Go first to a cell phone waiting area then proceed to the deplaning curbside to pick up an arriving airline passenger and then immediately exit the airport. Go directly to a parking facility and park for the trip’s duration (e.g., a long-term parking patron). Go directly to the curbside area, drop off passenger(s), and then continue to a parking facility and park for the trip’s duration (e.g., a long-term parking patron). Go directly to a parking facility, accompany a passenger into the terminal (or greet an arriving passenger at the baggage claim area), and then exit the airport (e.g., a short-term parking patron). After landing at the airport, a passenger could go directly to a parking facility, retrieve his/her vehicle (which has been

airline passengers during the peak 60-minute period times the percentage of passengers selecting each travel mode, adjusted using lead (or lag) times, and • Dividing each volume by the corresponding vehicle occupancy, taking care not to double count the same passengers (e.g., those in courtesy vehicles transporting parking patrons). Exceptions are required for vehicles that may operate on a scheduled basis rather than in direct response to passenger demand (e.g., courtesy vehicles and scheduled buses). Regression equations that correlate vehicle trips generated to airline passengers to acres of airport property or other measures are provided in Intermodal Ground Access to Airports: A Planning Guide, the ITE Trip Generation Handbook, and other reference documents. Traffic volume estimates at commercialservice airports developed using such equations are not considered reliable because of the significant differences in the characteristics of each airport, including differences in airline activity peaking patterns and volumes; airline passenger demographics (e.g., trip purpose, place of residency, travel mode

21 Table 3-2. Typical vehicle circulation patterns—originating airline passengers. Travel mode

Circulation pattern


Private vehicles Drop off at curb, then exit Drop off at curb, then park—Hourly, remain Drop off at curb, then park—Hourly, then exit Drop off at curb, then park—Daily Parking Drop off at curb, then park—Economy Parking Direct to park—Hourly, remain for duration Direct to park—Hourly, exit immediately Direct to park—Daily Direct to park—Economy Direct to off-airport

31% 9 4 7 4 4 14 14 9 4 100%

Rental Cars Direct to rental car return Drop off at curb, then rental car return Direct to off-airport

73% 23 4 100%

Taxicabs Drop off, then exit Drop off, then hold area

83% 17 100%

Source: LeighFisher, July 2009, based on data gathered at Los Angeles International, Salt Lake City International, Tampa International, and other airports.

preferences); passenger circulation patterns on and off the airport; airport layouts; the availability of parking, public transit, and commercial ground transportation services; and other factors influencing traffic volumes. Traffic Generated by Visitors The volume of traffic generated by visitors accompanying departing airline passengers (i.e., well-wishers) and arriving airline passengers (i.e., meeters and greeters) can be determined by establishing the average number of visitors accompanying each airline passenger or group of airline passengers. The number of visitors accompanying a passenger is a function of airline passenger trip destination/purpose and the demographics of the local community. For example, a greater number of visitors is expected to accompany airline passengers traveling overseas for leisure purposes than those accompanying business passengers traveling on domestic flights. In some cities, passengers are greeted by a large extended family group, rather than one or two persons. Typically, visitors either (1) use only the curbside areas, (2) park (for a short period) while they accompany the airline passenger group to/from the terminal building, (3) park (for a short period) in a parking lot (or cell phone lot) and, having met the passenger

in the terminal building, return to their vehicle, drive to the curbside area to pick up the passenger, and then exit the airport, or (4) drop off passengers, park, and then return to the terminal to accompany the passengers to/from the gate (e.g., a passenger with special needs, such as an unaccompanied minor or a disabled passenger). The latter pattern (drop off and then park) has become less prevalent since 2001, because visitors are prohibited from accompanying an enplaning passenger to an aircraft gate or greeting a deplaning passenger at a gate. Similar to the travel times for airline passengers, visitor travel times shift from the scheduled aircraft departure and arrival times. (See Figure 3-1.) By far, most visitors travel to and from an airport in private vehicles. They rarely (i.e., less than 5%) use public transportation or other travel modes. Traffic Generated by Employees Estimating the volume of traffic generated by airport employees requires the following inputs. Volume of employees and their work schedules. On an average day, more than 10,000 people work at many large-hub airports and more than 1,000 people work at typical medium-


Figure 3-1. Sample airport visitor lead and lag time.


hub airports (see Table 3-3). These people are employed by the numerous employers located on an airport, as follows: • The airport operator, including third-party contractors

• • •

working for the airport operator or sponsor, if different (e.g., janitorial, parking operators, and bus operators), providing services that have been outsourced; The airlines, including flight crew, aircraft maintenance, and other employees who may not be working in the terminal building; Concessionaires and other terminal building tenants, such as rental car companies and the operators of newsstands, restaurants, and other retail establishments; Government agencies, including (at U.S. airports) the FAA, TSA, Customs and Border Protection, Immigration and Customs Enforcement, U.S. Postal Service, and (at some airports) the military; Air cargo shippers and forwarders; Fixed-base operators; and Construction contractors, including construction workers and subcontractors.

Airport-based employees, particularly those employed by the airlines and cargo handlers, work unusual hours, because all commercial airports operate 365 days per year, and many

operate 24 hours per day. Typically, the arrival and departure hours of employees at an airport do not coincide with regional commute hours or with an airport’s peak enplaning or deplaning hours. For instance, major shift changes for airline employees often occur between 5 A.M. and 6 A.M. and between 2 P.M. and 3 P.M. Another complicating factor is the presence of flight crews, who may only travel to/from the airport a few days per month. The trips made by flight crews at an origin-destination (O&D) airport are sporadic, but while on an assignment, they become like passengers at destination airports—requiring courtesy vehicle service or flight crew transportation services (i.e., chartered vans). Generally, employers are required to report the total number of their employees requiring security badges, but do not report the number of employees working on each shift, the starting/ending times of each shift, or the travel modes used by their employees. Other than at airports with transportation management programs or ride-share promotional programs, few airport operators have accurate data indicating the number of individuals working at the airport at any given time of day or the travel modes used by these individuals. Surveys of the employers located on an airport are necessary to determine the number of people working on the airport, their work schedules, travel modes, and circulation patterns. Without such data (or traffic surveys conducted at

Table 3-3. Number of employees at selected airports.

Airport Boston-Logan International Bush Intercontinental/Houston Chicago O’Hare International Dallas/Fort Worth International Denver International Fort Lauderdale-Hollywood International John F. Kennedy International Lambert-St. Louis International Las Vegas McCarran International Los Angeles International Phoenix Sky Harbor International Salt Lake City International San Diego International San Francisco International Seattle-Tacoma International Tampa International John Wayne (Orange County, CA) Mineta San Jose International Oakland International Omaha Eppley Airfield Portland International Sacramento International

Parking permits

Estimated average daily employees (b)

Hub size

Total employees (a)

Large Large Large Large Large Large

---28,654 -14,000


14,600 14,406 40,000 -17,400 4,700

Large Large Large Large Large Large Large Large Large Large Medium Medium Medium Medium Medium Medium

20,000 ---22,000 --12,500 -6,000 -4,750 --14,500 --

7,920 ---16,019 ------------

-19,000 8,000 40,000 8,000 13,026 3,000 -11,375 -1,000 -10,500 2,500 5,000 1,500

(a) Includes badged and unbadged. (b) Number of people working at the airport on an average day. Source: LeighFisher, based upon information provided by individual airport operators.


the entry/exit to employee parking lots), it is difficult to determine the number and pattern of employee vehicle trips. Employee travel mode choices. As noted, little data are available describing the travel modes used by employees on an airport. Data presented in ACRP Report 4: Ground Access to Major Airports by Public Transportation (2008), indicate that, at 14 airports for which data were available, about 98% of all employees working on the airport arrive and depart in private vehicles (with the exception of Boston-Logan, Chicago O’Hare, and Denver International Airports). Employee reliance on private vehicles is a result of (1) employees working nontraditional hours that do not coincide with the operations or the schedules of public transportation, (2) employees residing in locations not well served by public transportation (i.e., outside the central business district), (3) employees working in locations outside of the terminal area that are not well served by public transportation, and (4) the availability of free or very-low-cost employee parking on airport property. One indicator of the number of vehicles driven by employees on an airport is the number of parking permits or identification badges issued by the airport operator to these individuals. For example, in 1996, it was determined that 61% of the employees who were issued security badges at Los Angeles International Airport had also been issued parking permits. The surveys indicated that, on a typical day, 29% of all employees were absent due to staff schedules, vacation, illness, or working away from the office. Of those employees traveling to work on a typical day, it was determined that 64% drove alone, 33% participated in a ride-share program, and 3% rode public transit, biked, or walked. The average vehicle occupancy for those individuals traveling to work at Los Angeles International was 1.38 employees per vehicle. Because most of the large employers operate multiple shifts, about 25% of the daily employee-generated vehicle trips occurred during a single hour. These data are similar to those reported at BostonLogan International Airport, where about 40% of all employees are absent on a given weekday and about 25% of those working on a given day arrive between 6 A.M. and 10 A.M. Employee circulation patterns. The use of regional access roads and airport access roads by on-airport employees can be estimated by determining the minimum time path or minimum cost path between their places of residence and place of employment. Place of residence data, summarized at a zip-code level, can be obtained from parking permit applications or from databases of airport-issued security badges. The minimum travel routes between these locations and points of access to the airport can be determined using regional planning models or by planners familiar with the regional highway network.

Future employment and employee work schedules. Forecasts of employment and employee trips tend to be imprecise because reliable estimates of future employment generally are not available and changes in future employment do not correlate well with changes in airline passenger numbers. Historically, planners have estimated future employment assuming that the rate of growth in employment represents the average of the rate of growth in airline passenger and aircraft operations numbers. However, anecdotal information suggests that this assumption is no longer correct because the airlines appear to be reducing their numbers of employees in order to improve productivity levels and reduce costs. For example, the increasing share of passengers who obtain their boarding passes via the Internet or check their bags using electronic ticketing kiosks has reduced the need for ticket counter agents. It is suggested that additional research is required to develop methods for estimating the volume of traffic generated by employees on airports. Sample results. Using the steps presented above, the employee trip generation rates presented in Table 3-4 were developed as part of the Los Angeles International Airport Master Plan Update. These data are presented as an example of how employee trip generation rates can vary for a day or over specific hours, and this example is not intended as a suggested proxy for another application. Traffic Generated by Air Cargo Air cargo (including airmail) traffic includes the trucks transporting the cargo, the private vehicles driven by the employees in the air cargo terminals, and customer trips. This traffic is generated by air cargo facilities (cargo terminals) located away from the passenger terminal area, freight consolidators or forwarders, and small package deliveries made directly to the terminal area. It is recommended that the volumes of trips generated by trucks, delivery vans, and air cargo employees be estimated separately. Employee vehicle trips are the largest component of the traffic generated by an air cargo facility (over 70% of the total traffic volume, according to surveys conducted at Memphis and Los Angeles International Airports and other locations). The volumes of truck and delivery van trips generated by an air cargo facility (i.e., the trip generation rate) are unique to an individual airport and not transferable to other airports. The two measures (or dependent variables) related to air cargo that are most readily available—air cargo tonnage and the size of air cargo buildings—are not reliable indicators of the volume of cargo-related truck or total vehicle trips, largely because there are many different forms of air cargo service,

25 Table 3-4. Example of vehicle trips per employee working at Los Angeles International Airport. Employee trip generation rate (vehicle trips per employee) Morning peak Airport peak Afternoon peak (8 A.M. to 9 A.M.) (11 A.M. to 12 P.M.) (5 P.M. to 6 P.M.) Daily Inbound










Source: Leigh Fisher Associates, January 1996, using Los Angeles World Airports' ride-share database representing a typical weekday, Los Angeles International Airport Master Plan—Phase I, On-Airport Existing Transportation Conditions.

including integrated cargo handlers, all-cargo or heavy freight carriers, as well as import, export, and shipments that require special handling (e.g., flowers or fresh fish). Each form of air cargo may generate a different number of truck trips, operate at different truck arrival/departure times, and use different vehicle sizes. For example, a local overnight delivery service operation might have multiple tractor-trailers picking up and dropping off containers, as well as dozens of local single-unit delivery vehicles distributing packages locally. Conversely, a large import/export freight operation may only generate a few tractor-trailer trips. Thus, although airport operators have reliable statistics on air cargo tonnage transported, tonnage is not a reliable indicator of the volume of truck trips because the volume of trips is a function of the type of cargo service and freight activity, not cargo tonnage (or the size of the air cargo terminal).

As noted, air cargo is transported by a wide variety of cargo shippers, each having different trip generation rates. Little, if any, research has been published, or documented, on air cargo trip generation. Additional research is required to develop methods for estimating the volume of traffic generated by air cargo terminals at airports and the employees working in these terminals. Traffic Generated by Service and Delivery Vehicles Service and delivery vehicles include those vehicles (1) bringing goods and materials (other than air cargo) to/from terminal building loading docks, consolidated warehouses, and other sites on an airport, (2) transporting individuals performing airport maintenance and construction, (3) being used by airport police, fire, and emergency response staff, and (4) making trips not directly generated by airport passengers, employees, or air cargo. At most airports, little to no data are available on the current volume of service, delivery vehicle trips, or the activities generating these trips (i.e., the extent of goods and material deliveries, trash removal, emergency responses, or construction deliveries and traffic). Generally, no data are available to guide estimates of the future volume of service/delivery vehicle trips, or the extent of future activities generating these trips. Additional research is required on this topic.

Sample results. Although not considered applicable to all airports, the data in Table 3-5, developed for Los Angeles International Airport, present the estimated vehicle trips generated by different cargo facilities (including employee trips) per ton of air cargo. Data from Chicago O’Hare International Airport, circa 2004, indicate that a general-purpose cargo facility generated about 0.13 daily truck trips per 1,000 annual cargo tons.

Table 3-5. Estimated airport cargo trips per daily cargo tonnage at Los Angeles International Airport.

Cargo shipper International airline

Daily trips (in and out)

Facility peak hour Afternoon Morning In Out In Out

Commuter peak hour Morning Afternoon In Out In Out










Domestic airline










Overnight delivery service










Source: Leigh Fisher Associates, January 1996. Los Angeles International Airport Master Plan— Phase I, On-Airport Existing Transportation Conditions.


Traffic Generated by Other Airport Land Uses Other land uses commonly found at public airports include general aviation/FBO facilities and military bases. At most commercial-service airports, these other land uses do not generate significant volumes of traffic during the peak hours for the airport or regional highway network. When the analysis is focused on the airport terminal area and primary airport access roadways, the traffic volumes generated by these land uses are often ignored or considered to be “background” traffic and combined with that of service/delivery vehicles. Traffic volumes generated by general aviation are a function of the number of general aviation aircraft operations, and the type of aircraft (business jets, air taxis, or small propeller aircraft). Traffic volumes generated by military bases vary according to the type of base and its function. Traffic volumes generated by nonaviation land uses that are not related to airport or aviation activity (e.g., industrial parks or large retail centers) can be estimated using the ITE Trip Generation Manual. Traffic Generated by Nonairport Vehicles Using Airport Roadways Vehicles not related to the airport or airport land uses may use airport roadways as a shortcut to bypass congestion or delays on the regional roadway network. This traffic, commonly referred to as cut-through traffic, adds to airport roadway requirements and contributes to airport roadway congestion. Cut-through traffic occurs at airports having multiple entrance and exit points (e.g., Dallas/Fort Worth, Phoenix Sky Harbor, and Washington Dulles International Airports, and Bush Intercontinental Airport/Houston) and where the roadway network configuration allows nonairport traffic to share the airport roadways with airport-generated traffic. Most airport operators discourage such cut-through traffic. Determining the volume or proportion of existing cutthrough traffic may require recording and matching the license plates or electronic toll tags of vehicles entering and exiting the airport at all major airport entry and exit points (i.e., a license plate matching survey or toll tag survey). It is not possible to identify cut-through traffic volumes using simple traffic volume counts. Estimating the volume of future cut-through traffic requires an understanding of future regional land uses and expected regional traffic patterns/travel times. The volume of nonairport traffic using airport roadways is a function of the volume of traffic on the regional roadways, and the travel-time savings these vehicles would experience if they were able to use airport roadways as a shortcut. These time savings can be determined by comparing the travel times via airport roadways and on alternative routes, knowing the forecast congestion and travel

times on these routes as forecast by regional travel models or other sources.

Off-Airport Origin and Destination Points (Trip Distribution) Some non-hub and small-hub airports have single entry/exit points. At these airports, all vehicles enter and exit via one roadway. The regional approach and departure vehicle distributions may be required to determine the proportion of leftturn, right-turn, and trough traffic at the intersection of the airport roadway with the regional highway network. Many airports have multiple entrance/exit points—one serving the terminal area and separate entrances/exits for aircraft maintenance centers, general aviation terminals, military bases, or other land uses. Although the volume of traffic using each entrance/exit can often be determined by the land use(s) served by the specific entrance/exit, large airports may have multiple connections to the regional roadway system, where the use of each is determined by regional travel patterns (or a combination of regional travel patterns and the on-airport destination). For these large airports with multiple connections to the regional roadway system, it is necessary to know the routes drivers follow when traveling to and from the airport in order to analyze (1) the intersections or junctions of the airport access roadways and regional roadway network, (2) traffic volumes on airport roadways associated with specific connections to the regional roadway network, and (3) the effect of airport traffic on the regional roadway network. The routes drivers follow are a function of where they enter airport property and their on-airport destinations. These locations (or the distribution of these locations) are a function of airline passenger trip purpose, place of residency, regional land use patterns, the regional highway network, existing and forecast roadway congestion/travel times, the availability of public transit, and other factors. At airports having multiple entry/exit points serving the terminal area (or other major land use), drivers typically select the most convenient entry/exit point, which generally implies the point that minimizes travel time. It is possible to estimate the proportion (and thereby the volume) of vehicles using each entry and exit point by determining (1) the actual locations where motorists (including airline passengers, visitors, and employees) begin their trips to the airport (or end their trips from the airport) or the distribution of these locations, and (2) the most logical routes used by motorists from each of these origin or destination points. At many airports, fewer than 30% of all trips begin/end in the downtown area, with the remainder arriving from or going to places of residency and employment distributed throughout the region. A planner familiar with the regional


highway network can determine the most likely routes from the primary regional origin and destination points. In addition, these data (or trip distributions) can be obtained from surveys of airline passengers or, when such data are not available, from the local metropolitan planning organization, which can provide information on future distributions of places of residence and employment, a description of the future regional transportation network, and the likely travel paths or approach/ departure distributions.

Assigning Traffic Volumes to the Roadway Network (Trip Assignment) Assigning the traffic volumes generated by airline passengers, visitors, employees, air cargo, and service/delivery vehicles to the on-airport roadway network requires information as to (1) where these vehicles enter or exit the airport, (2) their final and interim destination or origination points on the airport, and (3) the routes or paths available to these vehicles. • Airport entry and exit points. The methodology for deter-

mining traffic volumes entering and exiting an airport at specific locations is provided earlier in this chapter (see Estimating Traffic Volumes [Trip Generation]). • Origin and destination points on the airport. The methodology for determining the volumes of trips associated with specific on-airport origins and destinations is also provided in the previous section on Estimating Traffic Volumes (Trip Generation). • Travel paths. Typically, on a regional roadway network motorists can select from several alternative travel paths. Thus, a sophisticated traffic assignment procedure is required to allocate these vehicle trips among the available travel paths (i.e., to assign the vehicle trips to the regional roadway network) and, if desired, allocate trips to alternative routes, as primary routes become congested and travel times decrease. In comparison, on an airport, there is generally only a single logical travel path available for airline passengers and visitors, employees, and air cargo vehicles. Thus, the traffic assignment process is much simpler at airports. At most airports, there is only one travel path available between the airport entry and exit points and the primary origin/destination points. For example, at most airports, there is only one route connecting the airport entrance/exit and the terminal curbside areas, public parking areas, or rental car ready/return areas. Exceptions include those airports having several entrances/ exits used by airline passengers, or having multiple terminal buildings served by separate roadways. Some large airports provide internal bypass roads allowing motorists to avoid

slow moving traffic at curbsides or other areas of potential congestion. Generally, at an airport, most motorists follow the guide signs directing them to the major on-airport destinations. Furthermore, most motorists will follow the prescribed routes even if they become congested, and typically deviate to a different route only if directed to do so by a traffic control officer. Most employees and service vehicle drivers follow the quickest route, unless they are prohibited from using specific roads, or tolls or fees are associated with the use of specific routes. The travel paths of originating airline passengers can be determined using the information presented in Table 3-1 (revised for the specific characteristics of the airline passengers and airport being analyzed), and the travel paths of terminating airline passengers can be determined using similar information. As noted, care must be taken when assigning trips made by passengers who use multiple travel modes (e.g., those who park in a remote parking lot and also use a courtesy vehicle) or multiple legs (e.g., those who go to the curb and then to parking). For example, assuming that 100 vehicle trips per hour are generated by originating airline passengers at an airport; 65% of these trips are generated by private vehicles; 30% of those private vehicles go to the curb and then go to parking, where they remain for their trip duration; and 80% arrive from the east and 20% arrive from the west, these assumptions result in 20 vehicle trips by private vehicles using both the curb and daily parking (100 × 65% × 30%), of which 16 vehicles enter from the east and 4 enter from the west. The trip assignment process for airport roadways requires (1) repeating this calculation for every combination of travel mode, circulation path, and regional approach/departure path, (2) assigning these vehicle trips to the corresponding roadway links, and (3) finally determining the sum of all vehicle trips assigned to each roadway link. The sum of the vehicle trips on each roadway link represents the estimated traffic volume on that link. Travel forecasting software or spreadsheet analyses are frequently used to perform this repetitive process, particularly when traffic forecasts are being prepared for large airport roadway networks. The use of these methods allows planners to readily test the implications of alternative assumptions regarding mode choice, travel paths, or airline passenger activity patterns, as well as saving time and effort.

Challenges with Estimating Roadway Traffic Volumes As noted, several challenges are associated with estimating roadway traffic volumes—either existing or future—using the traditional four-step travel forecasting techniques. Key


challenges encountered by most airport operators include the following.

these land uses and no reliable method exists for forecasting future trips.

Lack of Data on Airline Passengers

Effort Needed to Gather Required Data

Most airport operators do not conduct regular surveys of the travel modes used by airline passengers, the occupancies of vehicles transporting airline passengers, their lead and lag times, or their on-airport circulation patterns (e.g., the percent using parking or curbside areas). It is estimated that fewer than 20 U.S. airport operators regularly conduct surveys of the travel modes and circulation patterns of airline passengers and have access to current data.

Comprehensive surveys of originating and terminating airline passengers can be costly and time consuming to plan, authorize, and conduct, with several months required to review and summarize the resulting data before they are available for release to others.

Lack of Data on Hourly Passenger Volumes Many airport operators do not have accurate data on hourby-hour originating/terminating airline passenger numbers. At many airports, for planning purposes, hourly airline passenger numbers are calculated using (1) reported aircraft arrival and departure schedules, (2) aircraft sizes (and corresponding seat capacities) to determine the number of available seats per hour (or other time increment), (3) assumed load factors (by airline)—the portion of seats occupied by passengers, and (4) the assumed portion of originating or terminating passengers (by airline). A minor difference in the estimated load factor or the proportion of enplaned/deplaned passengers in the peak hour can lead to significant differences in the numbers of peak-hour passengers. Furthermore, although planners recognize that aircraft load factors vary throughout the day and by day of the week, typically, a single load factor is applied to all aircraft of a given airline. Similarly, while the percentage of passengers who originate or terminate at an airport may vary significantly throughout the day, typically only a single originating/ terminating factor is applied to all passengers of a given airline. Lack of Data on Airport Employees As previously noted, most airport operators have little or no data regarding the numbers of employees reporting to work on a daily basis, and less data on the hour-by-hour arrival/departure patterns and travel modes used by these employees. Few, if any, airport operators have forecasts of future employment that are considered to be as reliable as the available forecasts of airline passengers. Lack of Data on Air Cargo and Service/Delivery Trips As noted earlier, additional research is required on air cargo and service/delivery vehicle trips. At most airports, little data are available on the existing numbers of trips generated by

Resulting Accuracy As noted, forecasts of the traffic volumes generated by airline passengers are often prepared in substantially more detail than forecasts of traffic generated by employees, air cargo, or service/deliveries. However, although traffic generated by airline passengers may account for over 70% of the traffic during the peak hour, it typically represents less than half of the daily traffic generated by an airport. The costs and time required to gather the airline passenger data needed to forecast airline passenger vehicle trips should be compared with the benefits (i.e., anticipated level of accuracy).

Estimating Future Airport Roadway Traffic Volumes— Alternative Approach An alternative approach to estimating future airport roadway traffic volumes involves determining existing traffic volumes on each roadway segment (or major segments) and applying a growth factor to the peak-hour volume to represent future conditions. This alternative approach is commonly called the “growth factor method.” It is suitable for quick analyses of airport curbside and terminal area roadway operations for planning purposes. Compared to the fourstep forecasting approach, this approach can be applied relatively quickly and inexpensively. The growth factor method requires (1) determining the existing peak hour(s) roadway traffic volumes on each roadway segment or major segments, (2) developing growth factors, and then (3) multiplying the existing peak roadway traffic volumes by the selected growth factor to develop an approximation of future conditions.

Growth Factor Method for Estimating Future Traffic Volumes A growth factor is the ratio between traffic volumes in the current peak hour and in the peak hour to be analyzed. A growth factor can be based on the ratio of the forecast total annual airline passenger numbers (enplaned plus deplaned passengers) for the future year to be analyzed to the equivalent


existing airline passenger numbers. Seasonal growth factors can be developed to adjust for peak-month traffic operations using data commonly available at most airports. For example, seasonal factors can be developed using the ratio of parking revenues (or, preferably, public parking transactions) during the peak month to the revenues during the current month or the ratio of month-to-month airline passenger numbers.

Challenges with Use of the Growth Factor Method The major challenge with using the growth factor method is that it is relativity simplistic. This method is based on the assumption that existing patterns of activity and circulation will remain unchanged throughout the forecast period. This method also may not account for changes that may result from • New land uses on or near the airport that could affect the

paths that motorists follow when entering or exiting the airport.

• Changes in choices of travel modes, parking facilities, or

circulation paths that may result from new or improved public transportation services, changes in parking facilities or parking rates, or increases or decreases in the propensity of motorists to use curbside roadways. • Changes in the proportion of airline passengers during the future peak month, peak day, or peak hour, although these changes could be compensated for by adjusting the growth factor appropriately. For example, if the peak hour is expected to account for a smaller proportion of daily traffic due to anticipated changes in airline schedules or a “flattening” of the peak due to increased traffic volumes, the growth factor could be adjusted accordingly. • Changes in the roadway network on or near the airport. For example, the construction of a new major regional highway may affect how vehicles approach the airport and turning movement patterns at the airport entry/exit. Similarly, a new or modified airport roadway could alter internal traffic circulation and merging or weaving patterns on the airport.



Analyzing Airport Terminal Area Roadways

This chapter presents an overview of terminal area roadway analyses. It presents level-of-service definitions applicable to airport roadways and describes methods for estimating the capacity and levels of service. Chapter 5 presents comparable methods for analyzing curbside roadways. As described earlier, a hierarchy of analytical methods— including quick-estimation, macroscopic, and microsimulation methods for analyzing airport terminal area roadway and weaving section operations, is proposed. The appropriate analytical method will evolve as a project proceeds from concept to final design, and as more time and data become available to support the analyses. This chapter presents the suggested quick-estimation methods for analysis of airport roadways with uninterrupted flows, signalized roadways, and airport roadway weaving sections; the macroscopic method for analyzing low-speed roadway weaving areas commonly found on airports; and an overview of the use of microsimulation methods. The macroscopic methods and performance measures presented in the 2000 HCM are considered applicable for analyses of airport roadways with uninterrupted traffic flows and unsignalized or signalized intersections, but not for analyses of low-speed roadway weaving areas. It is suggested that the method presented in the section on Macroscopic Method for Analyzing Airport Roadway Weaving Areas be used when macroscopic analyses of airport weaving areas are required, and that the methods presented in the HCM be used for macroscopic analyses of all other airport roadways. The methods and data presented in this chapter represent the best available information concerning airport roadway operations and the consensus of the research team, the Project Panel, and other reviewers at the time this Guide was prepared. It is suggested that additional research be conducted on lowspeed weaving areas and maximum service rates for airport roadways.

Level-of-Service Definitions for Airport Terminal Area Roadways The key performance measures defining the level of service of an airport terminal area roadway are as follows: • Average speed, which determines travel time; • Traffic density, which determines the ability of motorists

to easily maneuver into and out of travel lanes; • Maximum volume-to-capacity (v/c) ratio, which indicates

how close the roadway is to breakdown and is useful for determining other performance measures such as queue length and delays; and • Duration and length of queues. With the exception of the weaving analysis discussed in this chapter, the definitions, metrics, and procedures presented in the 2000 HCM are applicable to airport roadways with uninterrupted operations and signalized and unsignalized (i.e., stop-sign controlled) intersections. The weaving analysis methods presented in the 2000 HCM (and the 2010 update) are primarily oriented toward operations on freeways or major arterial streets. At airports, weaving often takes place on roadway segments designed for speeds that are much slower than those on freeways or even on major arterial streets. As a result, although the weaving theory and methods presented in the 2000 HCM (and subsequent updates) are applicable to airport roadways, the metrics defining levels of service are not. Consequently, subsequent portions of this chapter present alternative metrics for the low-speed weaving that occurs on airport roadways.

Quick-Estimation Methods for Analyzing Airport Roadway Operations This section presents quick-estimation methods for analyzing uninterrupted flows, signalized roadways, and airport roadway weaving sections.


Quick-Estimation Method for Uninterrupted Flows on Airport Roadways Quick-estimation methods are most appropriate for “sizing” a roadway in the early stages of planning and the design process when little has been decided (or is known) about the details of the required roadway. Such methods are suitable for use when preparing airport master plans or terminal area plans to size or evaluate a roadway and identify points of existing or future constraints. Table 4-1, which is adapted from Exhibits 21-2 and 21-3 of the 2000 HCM, presents the maximum service flow rate and

adjusted flow rates for multilane roadways with uninterrupted flows. The adjusted flow rates represent the maximum flow rates of typical airport access and circulation roadways and were calculated assuming that (1) heavy trucks and buses represent less than 5% of the traffic volume on the access roadways, (2) courtesy vehicles and minibuses (which are assumed to be equivalent to recreational vehicles in terms of performance) represent about 10% of the traffic volume on access roadways, and (3) a high proportion of drivers who are infrequent users of, and are, therefore, unfamiliar with, the airport roadways. The free-flow speeds can be approximated by the posted speed limits on the roadway section unless drivers

Table 4-1. Levels of service for airport terminal area access and circulation roadways. Criteria


Minimum speed (mph) Maximum volume/capacity ratio Maximum service flow rate (passenger cars/ hour/lane) Maximum flow (vehicles/hour/lane) (a)

50.0 0.28

Minimum speed (mph) Maximum volume/capacity ratio Maximum service flow rate (passenger cars/ hour/lane) Maximum flow (vehicles/hour/lane) (a)

45.0 0.26

Minimum speed (mph) Maximum volume/capacity ratio Maximum service flow rate (passenger cars/ hour/lane) Maximum flow (vehicles/hour/lane) (a)

40.0 0.26

Minimum speed (mph) Maximum volume/capacity ratio Maximum service flow rate (passenger cars/ hour/lane) Maximum flow (vehicles/hour/lane) (a)

35.0 0.26

Minimum speed (mph) Maximum volume/capacity ratio Maximum service flow rate (passenger cars/ hour/lane) Maximum flow (vehicles/hour/lane) (a)

30.0 0.26

Minimum speed (mph) Maximum volume/capacity ratio Maximum service flow rate (passenger cars/ hour/lane) Maximum flow (vehicles/hour/lane) (a)

25.0 0.25

550 440

490 400

450 360

410 330

370 300

310 250

Level of service B C D Free-flow speed = 50 mph 50.0 50.0 48.9 0.45 0.65 0.86 900 730

2,000 1,620

Free-flow speed = 45 mph 45.0 45.0 44.4 0.43 0.62 0.82

42.2 1.00

1,550 1,250

1,900 1,530

Free-flow speed = 40 mph 40.0 40.0 39.0 0.42 0.61 0.82

38.0 1.00

740 600

1,170 940

1,400 1,130

1,750 1,410

Free-flow speed = 35 mph 35.0 34.0 34.0 0.42 0.61 0.80

33.0 1.00

670 540

1,060 860

1,280 1,030

1,600 1,290

Free-flow speed = 30 mph 30.0 30.0 29.6 0.41 0.60 0.79

29.0 1.00

600 480

980 790

1,150 930

1,450 1,170

Free-flow speed = 25 mph 25.0 25.0 24.8 0.40 0.59 0.79

24.0 1.00

500 400

870 700

740 600

990 800

mph = miles per hour (a) Flow rates adjusted to account for 0.95 heavy vehicle factor and 0.85 driver population factor due to occasional or unfamiliar users. Source:

47.5 1.00

1,710 1,380

810 650

1,300 1,050


LeighFisher, based on information presented in Transportation Research Board, National Research Council, Highway Capacity Manual, Exhibits 21-2 and 21-3, December 2000.

1,250 1,010


regularly exceed the posted speed limit, in which case the freeflow speed can be approximated by the average operating speed of the vehicles on the roadway. These adjusted flow rates also are based on the following assumptions: • Travel lanes are at least 12 feet wide. • Lateral clearances (e.g., distance from walls, abutments, or

other physical obstacles) are at least 6 feet on both the left and right sides of the roadway. • Any vertical grades are less than 0.25-mile in length or less than 3% (i.e., rises less than 3 feet per every 100 feet of length). • The roadways operate in one direction only, or for twoway roadways, at least two travel lanes are provided in each direction, separated by a median. The 2010 HCM includes tables that can be used to modify travel speeds and flow rates for conditions other than those described above. If the roadway being evaluated falls significantly outside the lane width, lateral clearance, percent of truck use, and varies from the other factors listed, then the traffic volume thresholds presented in Table 4-1 may not be accurate. A more detailed macroscopic analysis using procedures described in the 2000 HCM (or the 2010 update) may be necessary to determine the maximum service volume for the facility. If the lane width, lateral clearance, percent of truck use, and other factors described are applicable to the roadway being analyzed, then the information in Table 4-1 should be applied as follows: 1. Determine the free-flow speed for the roadway. The freeflow speed is usually determined by measuring the mean speed of traffic under very light flow conditions. However, the posted speed limit can be used as an approximation of the free-flow speed. 2. Determine the target level of service. The target is determined by individual airport operators (or local agencies) and reflects their individual policies and standards. If such a standard or policy is lacking, LOS D is a common standard for urban roadways, although many urban agencies have adopted LOS E as a standard. LOS C is considered the common standard for planning new airport facilities, although at large-hub airports, LOS D is sometimes considered to be acceptable on existing roadways during peak periods. 3. Using Table 4-1, select the appropriate free-flow speed and the column with the desired level of service. The maximum flow provides the maximum traffic per hour per lane that the roadway can serve in one direction. For example, if the free-flow speed is 50 mph and the target level of service is LOS D, then the maximum desirable flow rate for a two-lane one-way road would be 2,760 vehicles per hour (twice 1,380).

Quick-Estimation Method for Signalized Roadways The 2000 HCM (Appendix A, Chapter 10) presents a quickestimation method for roadways and signalized intersection operations that is considered applicable for analysis of airport roadways. An alternative quick-estimation method—the planning application of the critical movement analysis or Intersection Capacity Utilization (ICU) method—also is applicable to airport roadways with signalized intersections. The ICU method involves the following steps: 1. Identify the lane geometry. 2. Identify the hourly volumes, including left-turn, through, and right-turn volumes for each intersection approach. 3. Identify the signal phasing (i.e., which movements operate concurrently). 4. Perform left-turn check to determine the probability of each critical approach volume clearing the identified opposing or conflicting left-turn volume. 5. Assign lane volumes. 6. Identify critical volumes by identifying the conflicting or opposing traffic volumes (on a per lane basis) having the highest total volumes for each signal phase. 7. Sum the critical volumes. 8. Determine the intersection level of service. Appendix F of this Guide presents an explanation of the use of the planning application of the critical movement analysis method and a worksheet to guide users.

Quick-Estimation Method for Airport Roadway Weaving Sections Table 4-2 provides example data for a procedure for quickly estimating the maximum service volumes on airport roadway weaving sections for one-sided and two-sided weaving areas. These service volumes were developed using the macroscopic method described in the next section.

Macroscopic Method for Analyzing Airport Roadway Weaving Areas The 2000 HCM and the draft 2010 HCM provide methodologies for evaluating traffic operations on airport roadways. However, neither edition of the HCM is designed to evaluate weaving conditions for low-speed airport roadways (speed limits of 30 mph or slower). In fact, commercially available software for applying the HCM methods generally prohibit the user from applying the software to weaving sections with free-flow speeds lower than 35 mph. Consequently, a separate weaving analysis without the limitation on low free-flow speeds was developed and incorpo-

33 Table 4-2. Example service volumes for airport roadway weaving segments. One Sided Ramp Weave (single lane ramp) Service Volumes (vehicles/hour) for LOS B C D

Number of lanes in weaving section 3



















One Sided Ramp Weave (two lane ramp) Service Volumes (vehicles/hour) for LOS B C D


Number of lanes in weaving section 3



















Two Sided Ramp Weave Service Volumes (vehicles/hour) for LOS B C D


Number of lanes in weaving section 3




















(3 Lanes in this image)

(3 Lanes in this image)

(3 Lanes in this image)

Notes: Table uses arbitrarily selected volume combination with free flow speed of 35 mph, level terrain, weaving segment length of 500 feet, 5% heavy vehicles, and approximately 20% of traffic weaving. This table is an example of what service flows could be for one volume pattern and is not intended to function as a look-up table for a quick estimation method.

rated into a macroscopic model—the Quick Analysis Tool for Airport Roadways (QATAR). QATAR includes components that provide information about low-speed weaving and curbside roadway operations given certain inputs. The low-speed weaving operations are described in this section. The curbside operations components are described in Chapter 5. QATAR uses the weaving analysis calculations and methodology presented in Chapter 12 of the draft 2010 HCM for onesided and two-sided weaving, and applies these calculations to roadways having free-flow speeds slower than the lower bound of speeds presented in the draft 2010 HCM (free-flow speeds less than 35 mph). The draft 2010 HCM weaving methodology is described below so that analysts can follow its implementation within QATAR. Two modifications were made to the draft 2010 HCM weaving method to extend its application to lower speed roadway sections. First, the minimum speed for weaving traffic was reduced from 15 mph in the draft 2010 HCM materials to 10 mph. Second, special LOS threshold traffic densities were developed for application to weaving sections on low-speed airport roadways. As an input in determining the capacity of

the weaving segment, maximum service flow rates for basic freeway segments under base conditions were extrapolated to correspond to input free-flow speeds (i.e., less than 55 mph). The draft 2010 HCM presents macroscopic methods for analyzing airport roadway operations. These methods, if adjusted for the factors used to develop Table 4-1 (e.g., driver population, heavy vehicles, and roadway geometry), are applicable to analysis of airport roadways with uninterrupted traffic flows and flows controlled by signals or stop signs.

Use of Draft 2010 Weaving Analysis Procedures The draft 2010 HCM weaving analysis procedure involves the following steps, which are described in this section: 1. Collect and input roadway weaving section lane geometry, lane designations, free-flow speed, and peak hour volumes. 2. Adjust the mixed-flow traffic volumes to equivalent passenger car volumes (adjust for percent of heavy vehicles, driver familiarity, and peak-hour factor).


3. Determine configuration characteristic, which is based on lane changes of weaving movements. 4. Determine the maximum weaving length, if weaving analysis is appropriate. 5. Determine the weaving section capacity. 6. Determine lane-changing rates. 7. Determine the average speed of weaving and nonweaving vehicles. 8. Determine the level of service. The rest of this section describes these steps in more detail with the recommended modifications for applying this analysis to weaving sections of low-speed airport roadways. Additional detail on these steps is provided in the draft 2010 HCM. Collect and Input Data The analyst must collect data on existing and/or forecast peak-hour traffic volumes for each leg of the weaving section. The traffic data should include a peak-hour factor and percent of heavy vehicles. The peak-hour factor is the ratio of the total peak-hour flow rate in vehicles per hour (vph) divided by the peak 15-minute flow rate within the peak hour (converted to vph). The free-flow speed or posted speed limit should be observed (or estimated in the case of a new design or planning study). The proposed (or existing) lane geometry must be identified (number of lanes on each leg, number of lanes in the weaving section, lane striping showing how the lanes on each leg transition to and from the lanes in the weaving section, and the length of the weaving section). Adjust Flow Rates The mixed (passenger cars, trucks, buses, etc.) flow rates should be converted to the equivalent passenger car rates using the following formula: vi =

Vi (PHF )( f HV )( f p )

where vi = equivalent passenger car flow rate (passenger cars per hour, or pc/hr) Vi = the mixed flow rate (vph) PHF = peak-hour factor fHV = the heavy vehicle adjustment factor fp = driver familiarity adjustment factor The heavy vehicle adjustment factor is computed as follows: f HV =

1 1 + PT ( E T − 1) + PR ( E R − 1)

where PT, ET, PR, ER, are percentage and equivalence of trucks/buses and recreational vehicles in the traffic stream, respectively. The presence of recreational vehicles is typically negligible for airport facilities. Suggested truck equivalence is 1.5 for level terrain, which is typical for airport roadways. A peakhour factor of 0.9 is suggested in absence of field-collected data. For airport roadways where arriving and departing passengers constitute the predominant users, a value of 0.85 should be used for the driver familiarity adjustment factor (the full range should be between 0.85 and 1.0, with 0.85 representing unfamiliar drivers, and 1.0 representing regular commuters). The user has two options for entering traffic volumes through the weaving segment. The first option is to enter actual O&D counts (or volumes) on the weaving section, and the second option is to enter approach and departure volumes, and then use QATAR to estimate the weaving volumes in the segment. Determine Weaving Configuration Several key parameters characterize the configuration of a weaving segment. The first step is to determine whether the roadway being analyzed is a one-sided ramp weave or a twosided weave (illustrations are provided in QATAR as well as in Figures 4-1 and 4-2). The key variables in subsequent steps of the methodology for both types of weaving configurations are LCMIN = minimum rate at which weaving vehicles must change lanes to successfully complete all weaving maneuvers (lc/hr). NWL = number of lanes from which weaving maneuvers may be made with either one lane change or no lane changes. For one-sided weaving, this value is either 2 or 3, and for two-sided weaving, this value is always 0 by definition. For a one-sided weaving segment, the two weaving movements are the ramp-to-freeway and freeway-to-ramp flows; the following values are established: LCRF = minimum number of lane changes that must be made by one ramp-to-freeway vehicle to successfully execute the desired maneuver. LCFR = minimum number of lane changes that must be made by one freeway-to-ramp vehicle to successfully execute the desired maneuver. LCMIN = minimum rate of lane changing that must exist for all weaving vehicles to successfully complete their weaving maneuvers, lc/hr = (LCRF ⴱ vRF) + (LCFR ⴱ vFR). vRF = ramp-to-freeway demand flow rate in weaving segment, pc/hr.


Figure 4-1. Examples of airport roadway weaving configurations. (continued on next page)

vFR = freeway-to-ramp demand flow rate in weaving segment, pc/hr. For a two-sided weaving segment, only the ramp-to-ramp movement is functionally “weaving.” The following values are established: LCRR = minimum number of lane changes that must be made by one ramp-to-ramp vehicle to successfully execute the desired maneuver. LCMIN = LCRR ⴱ vRR vRR = ramp-to-ramp demand flow rate in weaving segment, pc/hr.

Determine Maximum Weaving Length The concept of maximum length of a weaving segment is critical to the methodology. Strictly defined, the maximum length is the length beyond which weaving turbulence no longer affects operations within the segment, or alternatively, no longer affects the capacity of the weaving segment. 1.6 L MAX = ⎡⎣5, 728 (1 + VR ) ⎤⎦ − [1, 566N WL ]

where VR is the ratio between weaving volume and total volume.


Figure 4-1. (Continued).

If the length of the weaving segment is greater than or equal to LMAX, then this weaving analysis methodology is not appropriate. The segment should then be analyzed as merge, diverge, and basic segments, as appropriate. Determine Capacity of Weaving Segment Weaving capacity is determined by two methods: density and weaving demand flows. The final capacity is the smaller of the results of the two methods. Weaving segment capacity determined by density. This is computed by c W = c IWL ⴱ N ⴱ f HV ⴱ fP where cIWL = capacity of the weaving segment under equivalent ideal conditions, per lane (pc/hr/ln) = cIFL − [438.2(1+VR)1.6] + [0.0765LS]+[119.8NWL]. N = number of lanes within the weaving segment. LS = length of the weaving segment. cIFL = capacity of a basic freeway segment with the same freeflow speed as the weaving segment under equivalent ideal conditions, per lane (pc/hr/ln), draft 2010 HCM,

Chapter 11, Exhibit 11-17, and interpolated for lowspeed airport access roadways. Weaving segment capacity determined by weaving demand flows. This is computed by c W = c IW ⴱ f HV ⴱ fP where cIW = 2,400/VR for NWL = 2 lanes. cIW = 3,500/VR for NWL = 3 lanes. With capacity determined, a v/c ratio for the weaving segment may be computed as follows: v c = V ⴱ f HV ⴱ fP c W Determine Lane-Change Rates The equivalent hourly rate at which weaving and nonweaving vehicles make lane changes within the weaving segment is a direct measure of turbulence in the flow of traffic (i.e., when vehicles exhibit irregular and apparently random fluctuations in speed). It is also a key determinant of speeds and densities within the segment, which ultimately determine the existing or anticipated level of service.


Type C weave. Vehicles entering from the lower left must make two lane changes to exit on the right. Vehicles entering from the lower right require no lane changes to exit on the left.

Unfortunately, these two equations are discontinuous, therefore, a third equation is introduced to bridge the gap between the discontinuity: LC NW3 = LC NW1 + ( LC NW2 − LC NW1 )[( INW − 1, 300 ) 650 ], where INW= a measure of the tendency of conditions to induce unusually high nonweaving vehicle lane-change rates. = [LS ⴱ ID ⴱ vNW] / 10,000, where ID is interchange spacing per mile. Final nonweaving vehicle lane-changing rate is defined as follows: LCNW = LCNW1 If INW ≤ 1,300: If INW ≥ 1,950: LCNW = LCNW2 If 1,300 < INW < 1,950: LCNW = LCNW3 If LCNW1 ≥ LCNW2: LCNW = LCNW2 Total Lane-Changing Rate. The total lane-changing rate LCALL of all vehicles in the weaving segment, in lane changes per hour, is computed as follows: LC ALL = LC W + LC NW Determine Average Speeds of Weaving and Nonweaving Vehicles in Weaving Segment

Figure 4-2. Example of weaving configurations.

Estimating the total lane-changing rate for weaving vehicles. This is computed by 0.5 0.8 LC W = LC MIN + 0.39 ⎡⎣( L S − 300 ) N 2 (1 + ID ) ⎤⎦

where LCW = equivalent hourly rate at which weaving vehicles make lane changes within the weaving segment, lc/hr. ID = interchange density, int/mi. Estimating the total lane-changing rate for nonweaving vehicles. Two models are used to predict the rate at which nonweaving vehicles change lanes in the weaving segment: LC NW1 = ( 0.206 v NW ) + ( 0.542L S ) − (192.6N ) LC NW2 = 2,1135 + 0.223( v NW − 2, 000 ) where vNW = nonweaving demand flow rate in the weaving segment, pc/hr.

The average speed of weaving vehicles in a weaving segment may be computed as follows: S W = SMIN + [( SMAX − SMIN ) (1 + W )] where SW = average speed of weaving vehicles within the weaving segment, miles/hour. SMIN = minimum average speed of weaving vehicles expected in a weaving segment, miles/hour; the recommended setting for low-speed airport roadways is 10 miles/hour. SMAX = maximum average speed of weaving vehicles expected in a weaving segment, miles/hour; the recommended setting for airport roadways is the posted speed limit (unless a speed survey or field observations by the analyst indicate that a different speed is appropriate). W = weaving intensity factor. = 0.226 ⴱ [LCALL / LS]0.789 The average speed of nonweaving vehicles in a weaving segment may be computed as follows: SNW = FFS − ( 0.0072LC MIN ) − ( 0.0048 v N )


Note that usually the nonweaving speed should be modestly faster than the weaving speed. However, the developers of the draft 2010 HCM weaving methodology believe that it is acceptable for the nonweaving speed to be slightly slower than the weaving speed in some cases. If the analyst finds that the nonweaving speed is more than 3 mph to 5 mph below that of the weaving speed, then it is recommended that the analyst recompute the weaving speed using a lower minimum speed of 5 mph (instead of 10 mph). The average speed of all vehicles in a weaving segment may be computed as follows: S = [ v W + v NW ]

[( v W

S W ) + ( v NW SNW )]

Determine Level of Service The level of service in a weaving segment, as in all freeway analyses, is related to the density in the segment. Density is computed as follows: D = [ v N] S where D is measured in pc/mi/ln Density is used to look up the level of service in Table 4-3. A special set of density thresholds has been developed for weaving on low-speed airport roadways. Airport operators may choose their own thresholds based on local experience and perceptions of quality of service.

Caveats Without more extensive research, it is impossible to know with certainty whether the results of the low-speed weaving

macroscopic model presented in this section are accurate, but the results can provide an initial indication of whether a weaving section with certain parameters might operate successfully or not. The results of the low-speed weaving analysis method and the revised metrics appear to correlate reasonably well with the observations of airport roadway weaving operations conducted as part of this research project, and produce results suitable for planning-level analyses of low-speed airport roadway weaving operations. Although low speeds can be entered as inputs to most microsimulation models, it is not known whether the resulting modeled traffic flows represent actual traffic operation patterns under those conditions—few, if any, studies have been conducted of the low-speed weaving conditions typical of airport roadways to allow full verification of the suggested low-speed weaving analysis method outputs. Significantly more observations at numerous locations are required to provide a basis for analysis of low-speed roadway weaving operations that is consistent with the level of analytical precision of the Highway Capacity Manual or any similar document. The proposed low-speed weaving method is not intended to serve as a basis for any of the following: • Design of a new low-speed roadway weaving section, • Design of modifications to an existing low-speed weaving

section, • A definitive operational analysis of an existing or proposed

weaving section, or • The assessment of the level of safety afforded by an existing roadway. Under the above conditions, microsimulation models may be more appropriate for evaluating traffic operations.

Table 4-3. Level-of-service criteria for weaving segments. Level of service A B C D E F

Freeway weaving segments (pc/mi/ln) 10 20 28 35 >35 v/c>1.0

Collector-distributor roadways (pc/mi/ln) 12 24 32 36 >36 v/c>1.0

Airport low-speed roadways (pc/mi/ln) 20 30 40 50 60 v/c>1.0

Notes: pc/mi/ln = passenger cars per mile per lane. If the density exceeds the LOS threshold, then the roadway is over capacity. Source: Transportation Research Board, Draft Highway Capacity Manual, Exhibit 12-10, 2010 (except for airport low-speed roadways).


Use of Microsimulation Methods Microsimulation modeling is an analytical process that uses sophisticated computer programs to analyze traffic operations for complex roadway systems. In microsimulation modeling, individual imaginary vehicles are assigned characteristics, such as a destination, vehicle performance capabilities, and driver behavioral profiles. Each “vehicle” then travels through a computerized roadway network, and various aspects of its performance are recorded during its simulated trip based on its interactions with other vehicles and traffic controls. These performance statistics can be summarized in many ways, including performance measures commonly used by traffic engineers and transportation planners (e.g., delays, travel times, travel speeds, and queue lengths). Some aspects of roadway systems, such as intersections controlled by isolated or coordinated traffic signals, can be analyzed using simpler techniques than microsimulation. The use of microsimulation models can be beneficial in other roadway environments, including those with complex traffic movements, such as weaving operations where some vehicles are entering, some are exiting, and some are traveling through the weaving sections. Many airport roadway systems are sufficiently complex to warrant the use of microsimulation. The use of microsimulation models should be considered if simpler analytical tools and methodologies do not yield reasonable results, provide sufficient detail, or cannot be used because the roadway configuration or operating conditions are outside the range of those addressed in the HCM. However, the use of microsimulation models and analyses of traffic using these models are relatively complex tasks requiring training in the use of the specific model and experience in traffic engineering to fully understand the simulation process so that appropriate inputs are used and the outputs are interpreted correctly. Most microsimulation software packages also require significant time to learn. Suggested guidelines on when microsimulation is probably not needed are as follows: 1. Signalized or unsignalized intersections can usually be analyzed using methodologies in the 2000 HCM unless exclusive left-turn lane storage area overflows are a significant problem. In such cases, HCM methodologies may yield optimistic estimates of signal performance, and microsimulation modeling may yield more accurate results. 2. Roadway segments having few or no driveways or intersecting side roads. 3. Weaving segments with two entries and two exits and a reasonable distance (e.g., at least 500 feet) between the entrance

to, and exit from, the segment, and free-flow speeds of 35 mph or greater. 4. If the use of a simpler technique—even if the inputs are outside of the recommended ranges—yields outputs that are consistent with observed conditions (e.g., traffic seems very congested, and use of the HCM methodology yields LOS E or F). Guidelines regarding when to consider microsimulation: 1. Signalized or unsignalized intersections that have more than four legs or are oriented in atypical ways. The analyst should initially attempt to use HCM methodologies and then consider microsimulation modeling if the inputs required to evaluate the roadway segments do not correspond to the HCM analysis structure. 2. Airport roadway segments with the number of lanes changing along the length of the segment and with multiple, and possibly unusual, orientations of driveways or intersecting side roads. 3. Weaving segments that do not fit the orientation of the weaving analysis in the HCM. This could mean more than two entries or exits, dimensions or speeds outside the bounds defined in the HCM, signals or stop signs within the weaving segment, etc. 4. If simpler techniques are used to analyze what appear to be sufficiently simple facilities, but the results indicate operations that are much worse or much better than those observed. 5. When congestion on one roadway section causes queues or backups that extend back and interfere with operations on an upstream critical roadway section. 6. When congestion on one roadway section significantly restricts the volume of vehicles that can arrive at a downstream critical location. 7. When comparing the congestion resulting from different improvement options for situations where it is not possible to design sufficient capacity to eliminate significant congestion. In this case, comparisons are typically made of the extent of the congestion (duration and length of queues) produced by the various improvement options. Microsimulation modeling is the best available tool for making these comparisons. FHWA’s Traffic Analysis Toolbox III: Guidelines for Applying Traffic Microsimulation Modeling Software (FHWA-HRT-04040, July 2004) provides additional information on the use and application of microsimulation. This document is available at htm.


Other Performance Measures At some airports, the adequacy of a roadway or curbside area has been defined by the length of time a motorist requires to enter and exit the terminal area. Microsimulation models can be used to establish a baseline condition and compare the baseline travel time (or a predetermined acceptable travel

time) with the travel times resulting from different levels of traffic demand and access and circulation roadway configurations. However, it is difficult to accurately estimate these travel times and queues without the aid of microsimulation models because of the relative short distances being analyzed and the difficulty in estimating queue lengths through other means.



Evaluating Airport Curbside Operations

This chapter presents measures of curbside roadway performance, definitions of curbside roadway levels of service, and a hierarchy of analytical methods for estimating curbside roadway capacities and levels of service. It also describes use of a macroscopic method, QATAR, for analysis of airport curbside roadways, and explains the use of this method. Appendix G documents the queuing theory and assumptions used in QATAR. In evaluating airport curbside roadway operations, analyses of both the curbside lanes (where motorists stop to pick up or drop off passengers) and the adjacent through lanes are required. As described in Chapter 2, these analyses are necessary because double- or triple-parked vehicles impede or delay the flow of vehicles in the adjacent through lanes.* As a result, the capacity of the through lanes decreases as demand for curbside space approaches or exceeds the capacity of a curbside roadway segment, causing double or triple parking. As described in more detail later in this chapter, the capacity of curbside pickup and drop-off areas depends on the number of lanes airport management allows to be used for vehicles to stop, load, or unload. For example, at airports where double parking is prohibited, curbside capacity equals the effective length of the lane next to the curb. At airports where double parking is allowed, curbside capacity equals twice the length of this lane. In this chapter, methods of estimating the volumes, capacities, and levels of service of the curbside lanes and the through lanes are presented separately. However, when estimating airport curbside roadway capacities and levels of service, it is

*Throughout this chapter, the term “parked vehicle” refers to a vehicle that has come to a complete stop and remains stopped to allow the loading or unloading of passengers and their baggage. Vehicles on curbside roadways are not “parked” in the same sense as vehicles in a parking lot or an on-street parking space because these parked vehicles may not be left unattended on airport curbsides. Within the airport industry, vehicles stopped or standing at curbsides are commonly referred to as parked vehicles.

necessary to consider the operations of both the curbside lane and the through lanes concurrently because the capacity and level of service of an airport curbside roadway system is determined by the component that has the lowest capacity or provides the poorest level of service. The methods and data presented in this chapter represent the best available information concerning airport roadway operations and the consensus of the research team, the Project Panel, and other reviewers. It is suggested that additional research be conducted to refine the estimated airport curbside roadway maximum service rates (i.e., the maximum flow rates at each level of service).

Performance Measures Curbside utilization is the recommended performance measure for airport curbside roadways. Curbside utilization indicates the ability of a roadway to accommodate existing or projected requirements for vehicles loading or unloading at the curbside. It also indicates if spare capacity is available to serve additional demand and surges in demand. Roadway and curbside capacities are typically analyzed for the peak hour or design hour of a facility. For airport roadways, it is suggested that the design hour be a typical busy hour on the peak day of the week during the peak month. This suggestion is in contrast to planning for airfield and other airport facilities, which often considers the peak hour of an average day during the peak month. Typically, a utilization factor of 1.30 or less (65% of the capacity of the curbside loading/unloading lanes) is a desirable planning target for new curbside roadways. A utilization factor of 1.70 (85% of the combined capacity of the inner and second curbside lanes) is acceptable for existing facilities, recognizing that during peak hours and days of the year, demand will exceed capacity. However, individual airport operator policies regarding parking in multiple lanes may dictate different utilization factor planning targets.


Utilization is an indicator of curbside roadway level of service, which provides an overall indication of the quality of the experiences of drivers and passengers using the curbside roadway. LOS C is a desirable planning target for a mediumor small-hub airport, both for the design of new curbside roadways and for analyzing an existing facility. LOS D is acceptable for an existing curbside roadway at a large-hub airport, recognizing that on some peak days of the year, the level of service may decrease to LOS E or less. Level of service is estimated separately for through traffic and for curbside loading/ unloading traffic. When additional performance measures, as described below, are required to supplement curbside utilization, the analysis is conducted using a microsimulation model. Such supplemental measures cannot be accurately determined without the use of a microsimulation model, either quantitatively or in the field (i.e., they are difficult to quantify using field surveys). For example, the use of a microsimulation model would help document the ability of an existing curbside roadway to accommodate future demand, or to quantify the benefits resulting from alternative curbside improvement options. These supplemental performance measures include • Number of vehicles parked in the second and third lanes.

The number of through lanes blocked by parked or parking vehicles (and the proportion of the modeled hour during which this blockage occurs) is an indicator of the extent of roadway congestion. It is also an indirect indication of the ability of motorists to enter/exit and stop at their preferred curbside locations since it is difficult for motorists stopped in the curb lane to exit when triple parking occurs without the intervention of traffic control officers. • Queue length. Queue length is the number of vehicles waiting to enter the curbside roadway or a specific curbside parking area expressed in terms of the distance that the vehicle queue extends back from the curbside parking area or point of congestion. Queue lengths are estimated for different levels of probable occurrence. The mean queue length has a 50% probability of being exceeded some time during the hour. The 95% queue length has a 5% probability of being exceeded. The 95% queue length is typically used for design purposes. • Queuing duration. The queuing duration (in minutes) indicates how long the congestion will last, and is useful for comparing two potential design solutions, neither of which completely eliminates queuing. Ideally, the queuing duration is zero for a new curbside roadway, and less than one hour for an existing curbside roadway. • Average vehicle delay. Average vehicle delay consists of two components—through traffic delay and curbside loading/unloading delay.

Through traffic delay is the amount of time required for a vehicle to traverse the entire curb length. To determine through traffic delay, the unimpeded travel time for through traffic on the curbside roadway is subtracted from the actual travel time to obtain the amount of through traffic delay per vehicle. When designing a new curbside roadway, the delay to through traffic should ideally be near zero. For existing roadways, delays of up to 15 seconds per vehicle may be acceptable, recognizing that the delays could be significantly higher on peak days of the year. The acceptable amount of delay for through vehicles must be set by the airport operator based on the design of the landside circulation system and the number of other delays experienced by through vehicles on other portions of the roadway circulation system. For example, if through vehicles must pass several curbside loading/unloading areas, then delays at each curbside area will be less tolerable. Curbside loading/unloading delay is the amount of time a vehicle requires to pull into a curbside stall, load or unload passengers, and exit. The minimum time necessary to drop off or pick up a passenger during uncongested periods (i.e., the average dwell time) should be subtracted from the total average observed time to obtain the amount of curbside loading/unloading delay. Curbside delays of up to 30 seconds are acceptable when designing a new roadway. Delays of up to 60 seconds per vehicle are acceptable for existing roadways. As shown by the checkmarks in Table 5-1, use of these performance measures requires different analysis methods. When curbside roadways are being analyzed using microsimulation models, it is possible to consider the number of vehicles parked in the second and third lanes, the length and duration of curbside queues, and average vehicle speeds (or delays). Without the aid of microsimulation models, it is difficult to accurately estimate vehicle parking patterns, travel times and delays, and queue lengths because of the relatively short distances on curbside roadways being analyzed and the difficulty estimating queue lengths through other means. When curbside roadways are being analyzed using the quickestimation or macroscopic methods described in this chapter, the appropriate performance measures are curbside utilization and the corresponding levels of service.

Level-of-Service Definitions for Airport Curbside Roadways The primary element defining the level of service of an airport curbside roadway is the ability of motorists to enter and exit the curbside space of their choice (e.g., one near their airline door or other chosen destination). As roadway demand

43 Table 5-1. Recommended airport curbside performance measures. Performance measure

Quick estimation

Macroscopic analysis

Microsimulation analysis

Curbside utilization ratio Number of vehicles parked in second and third lanes Queue length Queuing duration Average vehicle delay

and congestion increase, motorists are required to stop in spaces farther away from their preferred destination. The motorist is required to either stop in a downstream or upstream curbside space, double park, or, in an extreme case, circle past the curbside area multiple times while searching for an empty space. The key performance measures defining the level of service of an airport curbside roadway are the • Number of vehicles parked or stopped in the curbside

lane, and the percent double or triple parked, or otherwise stopped, in a position that interferes with the flow of traffic in adjacent lanes. This number of parked vehicles is a function of curbside demand vs. available capacity. • Length and duration of queues at the entrance to the curbside area. • Average delay encountered by private and commercial vehicles entering and exiting the curbside areas. • Curbside utilization ratio, which is a comparison of the length of the vehicles stopped along the curbside and the effective length of the curbside (i.e., the total length less the space occupied by crosswalks or other areas in which vehicles, or certain classes of vehicles, cannot stop). As stated, most of these measures are obtainable only through microsimulation modeling. Therefore, level-of-service definitions for airport curbside roadways shown in Figure 5-1 and presented in Table 5-2 are based on curbside utilization ratios. These definitions and ratios were validated using focus groups of airline passengers, airport landside managers, and commercial vehicle operators, which were conducted as part of this research project. (Appendix E presents a summary of these focus group sessions.)

Estimating Airport Curbside Roadway Traffic Volumes Curbside roadway traffic volumes can be estimated using the same methods used to estimate airport terminal area roadway traffic (see Chapter 3): the traditional four-step travel forecasting method and the growth factors method. The key differences between estimating terminal area road-

way traffic and curbside roadway traffic include, for curbside roadway traffic, the need to prepare the following: • Separate estimates of vehicles stopping in a curbside lane

and through traffic vehicles. At small airports with a single terminal building and a short curbside area (e.g., less than 500 feet in length), the volume of through vehicles may equal the volume of vehicles stopping at the curbside. However, these volumes may differ at airports having (1) multiple terminal buildings or large concourses served by a common roadway, (2) a curbside area with inner and outer curbside roadways separated by a raised island with midpoint entrances and exits, or (3) curbside roadways that are used by non-curbside traffic (e.g., vehicles entering or exiting parking areas, rental car areas, or other facilities). • Separate analyses of the departures curbside and arrivals curbside roadways. It is necessary to analyze these curbside areas separately because the departures and arrivals peak periods at an airport (and thus peak periods of curbside demand) occur during different hours of the day, and vehicle dwell times and space allocations (the proportion of curb length assigned to individual classes of vehicles) differ significantly at the departures and arrivals curbside areas, as described in subsequent sections of this chapter. At airports with dual-level curbside roadways, separate analyses of each level are required. At airports with a singlelevel curbside roadway, analyses of the peak periods for originating, terminating, and total passengers (originating plus terminating) are required. • Separate analyses for each class of vehicle. Private vehicles, taxicabs, limousines, door-to-door vans, courtesy vehicles, and charter buses/vans each have different dwell times, required vehicle stall lengths, and maneuvering capabilities. Furthermore, each service provided by these vehicles may have different operational methods and be governed by different airport regulations. For example, on an arrivals curbside, an airport operator may permit taxicabs to stand at the curbside for 30 minutes or more to ensure that waiting vehicles are available for arriving customers and may allow charter buses to remain at the curbside for 10 to 15 minutes to ensure that all members of a large party have claimed their bags and boarded the vehicle, but may only allow


Source: LeighFisher.

Figure 5-1. Curbside levels of service.

45 Table 5-2. Level of service criteria for airport curbside roadways.



Airport curbside levels of service B C D E

When double (and triple) parking is allowed at the curbside Maximum demand for curbside standing or parking/effective curbside length (a) 0.90 1.10 1.30 Maximum service flow rate 5-lane curbside roadway (vph) 3,400 3,280 3,100 4-lane curbside roadway (vph) 2,830 2,790 2,680 3-lane curbside roadway (vph) 2,200 1,950 1,580 When double parking is prohibited at the curbside Maximum demand for curbside standing or parking/effective curbside length (a) 0.70 0.85 1.00 Maximum service flow rate 4-lane curbside roadway (vph 2,830 2,830 2,800 3-lane curbside roadway (vph) 2,350 2,250 2,000 Maximum through lane volume/capacity ratio 0.25 0.40 0.60





2,710 2,220 860

2,400 1,800 750

Up to 2,400 Up to 1,800 Up to 750




2,730 1,760

2,600 1,600

Up to 2,600 Up to 1,600




vph = vehicles per hour (a) The ratio between the calculated curbside demand and the available effective curbside length. Source: Jacobs Consultancy, November 2009.

hotel/motel courtesy vehicles to stop while actively boarding passengers. • Separate estimates of traffic volumes for each terminal building or concourse. The peak periods of activity for each airline serving an airport may occur during different hours of the day. At airports with multiple terminals or large concourse(s) dominated by a single airline, the largest traffic volumes (and curbside area requirements) may occur during a different hour (or different 15-minute period) at each terminal or near each concourse. In addition, motorists prefer to stop at the curbside area nearest the doors (or skycap podiums) serving their airline (or that of the passenger they are transporting). Thus, demands are not distributed uniformly along the length of a curbside—particularly at airports with multiple terminals or large concourses—but are concentrated at the curbside areas corresponding to the airlines serving the largest volume of passengers during the peak period. As a result, at airports with several terminals or multiple concourses, the traffic volumes and curbside area requirements that correspond to (or are generated by) each terminal or concourse should be estimated. These estimates can be prepared by allocating the total peak-hour traffic volumes to each curbside area according to the percentage of total demand served by each area during the peak hour. The percentage of total demand served by each area can be estimated by analyzing (in decreasing order of reliability) the proportion of (1) peak period originating (or terminating) passengers served by each terminal building or concourse, (2) the number of scheduled aircraft seats served by

terminal or concourse during the peak period, or (3) the number of aircraft gates served by each concourse. If the data are available, it is preferable to estimate the traffic volumes generated by each terminal curbside area (by type of vehicle) separately, as the demographic and/or travel mode choices of the passengers on each airline may differ. For example, the curbside operations at a terminal primarily serving international passengers will differ from curbside operations at a terminal serving regional aircraft or short-haul domestic flights. However, as stated in Chapter 3, such airline passenger data require surveys of airline passengers and are available at few airports.

Estimating Airport Curbside Roadway Capacity and Level of Service Estimating airport curbside roadway capacities and levels of service requires analyses of both the curbside lanes and the through lanes because the numbers of vehicles parked in the curbside lanes affect the flow of vehicles in the through lanes; as curbside lanes approach capacity, the capacity of the adjacent through lanes is reduced. The capacity of a curbside roadway is defined as the smaller of (1) the number of vehicles that can be accommodated in the curbside lane(s) designated for loading or unloading or (2) the volume of through vehicles that can be accommodated in the through lanes.


Establishing Curbside Lane Capacity Curbside lane capacity is typically estimated in terms of the area (and the number of lanes) that the stopped vehicles may occupy while loading or unloading. Since vehicles stop in a nose-to-tail manner at most airports, this area is described as the effective length of curb measured in linear feet. Effective length is defined as the total length of the lane less (1) any space unavailable for public use because it is reserved for crosswalks, disabled motorists, or specific classes of vehicles (e.g., taxicabs or public buses) and (2) space located beyond the ends of the terminal building or adjacent to columns or other physical barriers that discourage its use by motorists because passengers cannot easily open their doors or easily enter/exit a vehicle. The number of stopped vehicles that can be accommodated in the curbside lane(s) (i.e., the capacity of the curbside lanes) varies depending on the number of lanes in which airport operators allow vehicles to routinely stop to load or unload passengers and their baggage. Airport operators establish specific policies concerning double parking that reflect the width of their curbside lanes, enforcement policies and capabilities, customer service, and use by private and/or commercial vehicles. Airports Where Double Parking Is Prohibited At airports where double parking is prohibited, the number of vehicles that can be accommodated in the curbside lane is equal to the effective length of a single curbside lane. Some airport operators restrict curbside parking or standing to a single lane for operational reasons (e.g., a narrow curbside roadway or curbsides used exclusively by commercial vehicles where double parking is prohibited). This description of the number of vehicles that can be accommodated in the curbside lane also applies to curbside roadways with a maximum of three lanes. This is because on a curbside roadway with three lanes only a single through lane would be available if double parking were to occur, which would lead to frequent bottlenecks (e.g., when a doubleparked vehicle or an open door of such a vehicle intrudes into the third lane). Thus, a single through/maneuvering lane for a significant portion of the curbside length is considered unacceptable and double parking is generally not tolerated on curbside roadways with a maximum of three lanes. Airports Where Double Parking Is Allowed At airports where double parking is allowed on the curbside roadways, the number of vehicles that can be accommodated at the curbside is equal to twice the effective curbside length. At airports where double parking is regularly allowed, pavement markings typically have been installed designating the lane next to the sidewalk plus the adjacent lane for pas-

senger drop-off or pickup, or where enforcement policies allowing double parking have been established. On roadways where double parking is allowed, if the roadway were operating at full capacity, the stopped vehicles would not be evenly distributed along the length of the two curbside lanes, and some motorists would choose to triple park next to the most desirable doorways or other locations. Additional Considerations At airports with inner and outer curbside areas available for use by private vehicles, these areas have different effective capacities, even if they are the same length. Motorists prefer to stop at the most convenient space available (e.g., the inner curbside lane), even if they observe downstream congestion or delays on this roadway. Thus, it is necessary to “discount” the capacity of the outer, less convenient curbside area if both areas are allocated to private vehicles. If one curbside is allocated to private vehicles and the second is allocated to commercial vehicles, such discounting is not required. For example, motorists approaching the departures curbside at Salt Lake City International Airport can use the curbside area adjacent to the terminal building or an alternative curbside area within the adjacent parking garage. Passengers using the alternative curbside are provided with a grade-separated path to/ from the terminal building and are offered skycap service on Delta Air Lines. Notwithstanding the good access, good directional signage, and amenities available, motorists are reluctant to use the curbside area within the parking garage, even when the curbside area adjacent to the terminal is congested. Consequently, it is suggested that, when calculating the capacity of a similar curbside configuration at other airports, it is necessary to adjust (or discount) the actual length of curb space within a garage (or other supplemental location) to determine its effective capacity. This adjustment is necessary because, if both the primary and supplemental curbsides are allocated for private vehicle use, the supplemental curbside will provide less capacity (even though it may be the same length) than curb space adjacent to the terminal building because it attracts fewer passengers. This discount factor is similar to operational factors, presented in the 2000 HCM, used to calculate roadway capacity and account for population factors, lane widths, rolling terrain, or unfamiliar drivers. No published research provides guidance on this discount factor, but the factor appears to vary according to the traffic queues caused by downstream congestion, local enforcement policies, availability of skycap service and dynamic signage, and the demographics of the passenger market (e.g., the proportion of frequent travelers or those traveling primarily with carry-on baggage). It is suggested that analyses be guided by field observations of existing conditions, which would reflect the unique characteristics of the airport and its passengers. If


field data are unavailable, it is suggested that the capacity of the supplemental curb space located in a garage be discounted by 50% and that the capacity of an outer curbside be discounted by 20% to 30%. Alternative Curbside Configurations It is assumed in the above discussions that vehicles stop in the curbside lane in nose-to-tail configuration. However, at some airports, the curbside areas are configured with pull-through spaces or 45-degree stalls. (See Chapter 2 for illustrations of alternative curbside configurations.) The above methods are applicable to these configurations with the exception of the sample vehicle dwell times and through-lane capacities discussed in the following section.

Calculating Curbside Lane Requirements Quick-Estimation Method This method is appropriate for use during the early planning and design stages for a new curbside when little is known about the details of the curbside design or layout. This method is used to compute the curb length required to serve a given demand, but it does not provide specific results on performance, such as average delay or queuing probability. A curbside lane can be considered as a series of stopping spaces, each capable of accommodating one vehicle. The average number of vehicles each space can serve during a given time period is inversely proportional to the average length of time (referred to as the vehicle dwell time) a vehicle occupies a space. For example, if the average vehicle dwell time is 3 minutes, then each space can accommodate, on average, 20 vehicles per hour. If the peak-hour volume is 160 vehicles, then (with the assumed average dwell time of 3 minutes per vehicle), the required curbside length is equivalent to eight spaces or 200 linear feet (assuming an average space length of 25 feet for illustrative purposes). This can be represented mathematically as R a = V ⴱ Di 60 ⴱ L where Ra = the average curbside length required to accommodate the vehicles stopping at a curbside area. V = the hourly volume of vehicles stopping at a curbside area. Di = the average vehicle dwell time (in minutes). L = the average vehicle stall length. This formula represents a condition where a single class of vehicles is using a curbside area (e.g., a curbside serving private vehicles exclusively), or where the requirements are developed assuming that all vehicles can be represented using average dwell times and a single stall length. More accurate

estimates can be developed by considering, separately for each class of vehicle, the hourly volume, the distribution of dwell times (rather than average dwell time), and average vehicle length. Additional accuracy can result from consideration of the peak periods within the peak hour (e.g., analysis of the peak 15 or 20 minutes) and the nonuniform distribution of demand along the curbside lane caused by a concentration of traffic at specific airline doors or other attraction points. The nonuniform arrival rate and distribution of vehicles can be reflected using statistical factors (e.g., a Poisson distribution). Table 5-3 presents data, gathered at the airports serving Memphis, Oakland, Portland, San Francisco, and Washington, D.C. (Dulles), used to calculate curbside lane requirements by class of vehicle, the application of a Poisson distribution (or adjustment) factor, and the resulting curbside requirements. The table presents examples of average curbside dwell times and vehicle stall lengths based on observations of post2001 curbside roadway operations at the airports, the estimated curbside requirements (i.e., design length) for five zones (two zones on the enplaning curbside and two zones plus a courtesy vehicle lane on the deplaning curbside). A comparison of the estimated requirements with the available curb length yields utilization factors for each of the five zones. As shown, two of the zones are substantially over capacity as evidenced by the utilization factors over 2.0. The quick-estimation method involves the following steps: 1. Determine peak-hour traffic volume from field survey or estimates of future traffic. 2. Determine the vehicle mix. If vehicle mix is unknown, assume that private vehicles represent 70% to 80% of the total traffic volumes, taxicabs and limousines represent 5% to 10%, courtesy vehicles represent 5% to 10%, and vans/buses/public transit represent 5%. 3. Determine the average vehicle stall length. Use the de facto values shown in Table 5-3 or the QATAR model (see Figure 5-3) or measure representative values, particularly for unusual vehicles or atypical parking configurations. 4. Determine vehicle dwell times using field measurements or the de facto dwell times shown in Table 5-3 or the QATAR model (see Figure 5-3). 5. Calculate curbside stall requirements that are equal to the volume multiplied by vehicle dwell times divided by 60 minutes. 6. Determine curbside design stall requirements that are equal to the curbside stall requirements times a probabilistic factor applied to the total curbside stall requirements (if a mixed-use curbside such as a typical departures curbside) or to an individual class of vehicles (if curb space is allocated to this classification), ranging from 3.0 for requirements less than 5 curbside stalls to 1.2 for curbside stall requirements of 100 or more.

48 Table 5-3. Estimate of terminal building curbside requirements—sample calculation.


Hourly volume (vph)

Average curbside dwell time (minutes)

Enplaning level, north Private vehicles Taxicabs Limousines Door-to-door vans (b) Courtesy vans (b) Scheduled buses (b) Total

621 52 9 38 24 10 754

3 2 2.5 3 4 5

Enplaning level, south Private vehicles Taxicabs Limousines Door-to-door vans (b) Courtesy vans (b) Scheduled buses (b) Total

363 35 6 38 24 10 476

3 2 2.5 3 4 5

Deplaning level, north Private vehicles Limousines Total

580 5 585

5.2 5.2

Deplaning level, south Private vehicles Limousines Total

345 4 349

5.2 5.2

Deplaning level courtesy vehicle lane Courtesy vehicles (b)



Required curbside stalls

31.0 2.0 0.4 1.9 1.6 0.8

18.0 1.0 0.3 1.9 1.6 0.8

50.0 0.4

30.0 0.3


Required design stalls (a)

40 5 2 3 3 1

25 3 1 2 3 1

62 1

39 1


Vehicle stall length (feet)

25 25 30 30 30 50

25 25 30 30 30 50

25 30

25 30


Design length (feet)

Existing curb length (feet)

Curbside utilization factor

1,000 125 60 90 90 50 1,415



625 75 30 60 90 50 930



1,550 30 1,580



975 30 1,005






(a) Represents calculated stall requirements adjusted to reflect random arrival of vehicles and nonuniform distribution of traffic volumes and demands using Poisson statistical probability factors. (b) Assumes that this mode makes a single stop at the curbside. Source: LeighFisher, November 2009.

7. Determine curbside design length that is equal to the number of design stalls times the average vehicle stall length 8. Calculate the utilization factor that is equal to the curbside design length divided by the existing curb capacity (or effective length) considering whether double parking is allowed by the airport operator. As defined previously in this chapter, a curbside utilization factor equal to or less than 1.3 is considered acceptable for a new design, while a utilization factor equal to or less than 1.7 is considered acceptable for existing curbside roadways. Macroscopic Method Alternatively, the curbside lane can be considered a series of processing points (or servers) and traditional queuing analyses can be used to calculate the capacity of individual servers

and the total capacity of the curbside lane. The macroscopic method (QATAR) described in the upcoming section on Analytical Framework Hierarchy for Airport Curbside Roadways uses queuing analysis to estimate curbside capacity. The following subsections describe the calculations of through-lane capacity and curbside capacity.

Calculating Through-Lane Requirements The requirements for curbside roadway through lanes depend on the areas they serve. At airports with a single terminal building and a short curbside area, the volume of through vehicles may equal the volume of vehicles stopping at the curbside. As discussed in previous chapters, factors that may result in higher volumes of traffic in the through lanes include vehicles bypassing a curbside area (1) that does not serve their airline (e.g., a different terminal building or major


concourse), (2) that is reserved for other classes of vehicles (e.g., authorized commercial vehicles), or (3) to enter or exit parking, rental car, or other land uses not related to curbside activities. As noted, bypass traffic proceeding to another terminal (as opposed to through traffic proceeding to a downstream portion of the curbside lane) may represent a significant portion of the total curbside roadway traffic volume. When these conditions occur, it is necessary to use the methods described in Chapter 4 to estimate the volume of traffic associated with the alternative land uses and/or to assign traffic volumes to each curbside roadway section (or airline) and class of vehicle. The capacity of a curbside roadway through lane is measured using methods similar to those described in Chapter 4 for other airport terminal area roadways, adjusted to account for the presence of double- or triple-parked vehicles. As noted previously, double- and triple-parked vehicles block or delay the movement of vehicles in through lanes, because through traffic must decelerate and maneuver around these stopped vehicles. As a result, through-lane capacity decreases when curbside lane demand exceeds the available capacity of a specific curbside segment (as opposed to the entire curbside length), and vehicles are double or triple parked. The reduction in through-lane capacity resulting from increased curbside lane demand can be estimated using commercially available microsimulation models capable of simulating airport curbside roadways or using QATAR (discussed later in this chapter). Alternatively, the approximations shown in Table 5-2 can be used to estimate curbside roadway lane capacities. Curbside roadway capacity must also be reduced when atgrade pedestrian crosswalks are present. The extent of the capacity reduction is a function of the volume of pedestrians crossing the roadway since the amount of time motorists must wait for pedestrians increases with pedestrian traffic. For example, if a crosswalk is controlled by a traffic signal, and if the signal allocates 25% of the green time during each hour to pedestrians, then capacity of the curbside roadway would be 25% less than if there were no crosswalk. If, instead of a signal, crosswalk operations are controlled by a traffic control officer, then a similar approximation can be made by observing curbside roadway operations. If the crosswalk is uncontrolled, then the behavior of motorists (do they stop when a pedestrian enters a crosswalk?) and the volume of pedestrians need be considered.

Additional Considerations in Estimating Commercial Ground Transportation Vehicle Curbside Requirements The analytical methods used to estimate curbside traffic volumes presented in Chapter 4 are applicable to private

vehicles and commercial ground transportation vehicles, the volumes of which can be directly correlated to airline passenger demand (e.g., limousines, taxicabs, and door-todoor vans dropping off passengers). However, these analytical methods are not applicable to vehicles that are allowed to remain at the curbside for extended periods (e.g., taxicabs and door-to-door vans standing in queues waiting to pick up passengers) or that operate on a scheduled or de facto scheduled basis (e.g., courtesy vehicles that generally operate on fixed headways regardless of the number of passengers transported). Allocation of Curb Space Generally, airport operators do not reserve space for commercial ground transportation vehicles dropping off airline passengers, with the exception of vehicles, such as public buses, that drop off and pick up passengers at the same curbside space. The amount of space allocated to commercial ground transportation vehicles picking up passengers is generally determined by airport management considering such factors as • Customer expectations. Deplaning airline passengers gen-

erally expect taxicabs to be available immediately adjacent to the baggage claim area, or visible from the exit doors. Passengers who have reserved luxury limousines expect a higher level of service than those choosing public transportation (e.g., baggage assistance, shorter walking times, minimal wait time). • Operational needs. To minimize the wait times of deplaning passengers, taxicabs are generally allowed to wait at the deplaning curbside area in queues of 3 to 10 vehicles. The number of taxicabs in the queue is a function of airport policy, the proximity of a taxicab hold area (where additional taxicabs may wait until dispatched to the curb), and the availability of curb space. Similarly, door-to-door vans are generally allowed to wait at the deplaning curbside, with the number of vans a function of the number of regional destinations served, number of van companies, airport policies, and available curb space. • Space requirements. In analyzing the amount of space to be allocated to each class of commercial vehicle operator (e.g., hotel/motel courtesy vehicles), the number of vehicles that will use the space concurrently (which is based on the number of operators and the frequency with which they serve the airport), and the permitted vehicle dwell times and vehicle sizes must be considered. • Vehicle maneuverability. In determining the amount of curb space to be allocated to each class of commercial vehicle operator, consideration should be given to the maneuverability requirement of the vehicles used (e.g., vans,


minibuses, or full-size buses) and, if appropriate, requirements of access to baggage compartments or baggage trucks. For example, a 45-foot-long full-size bus requires about 60 feet to stop parallel to a curb space. If a bus has an under-the-floor baggage storage compartment, curb spaces should be configured so that columns, sign poles, or other obstacles do not interfere with the opening of the baggage compartment. Vertical clearances. The ability of a full-size bus or other large vehicle to use a curbside area may be limited by the vertical clearance available (including low-hanging signs or drainage structures). For example, the minimum vertical clearances required are 13 feet for a full-size bus, 11.5 feet for the shuttle buses used by rental car companies, and 9 feet to 10 feet for courtesy vans serving hotels/motels. These dimensions can vary for those vehicles using compressed natural gas, having rooftop air conditioners, or having rooftop antennae. Some multilevel roadways can not accommodate full-size buses or over-the-road coaches used by charter bus operators. Competition. Commercial vehicle operators compete with private vehicles, other operators providing the same service, and operators providing services that are perceived as being similar (e.g., taxicab and door-to-door van operators). Each commercial vehicle operator generally wishes to be assigned space nearest the busiest terminal exit doors or space that is equivalent to or near the space provided to their competitors to maintain a “level playing field.” Airport management policy. Some airport operators have policies that encourage the use of public transportation and, thus, assign public transit vehicles the most convenient or most visible curb space. Revenues generated by commercial vehicle operations. Airport operators receive significant revenues from public parking and rental car concessions. As such, the courtesy vehicles serving on-airport parking lots and rental car facilities may be assigned higher priorities than other courtesy vehicles, including those serving privately operated parking or rental car facilities located off airport.

Number of Curbside Stops Made by Commercial Vehicles An additional factor to be considered when estimating the curbside roadway lane requirements of commercial vehicles is the number of stops each vehicle makes. For example, a single courtesy vehicle or public bus may stop two or more times along a terminal curbside, depending on the length of the curb and airport policies. The calculation of curbside lane requirements for each courtesy vehicle, for example, must be adjusted to account for the number of stops.

Analytical Framework Hierarchy for Airport Curbside Roadways Airport curbside roadway operations—particularly the reduction in through-lane capacity that results from increased curbside lane demand—can be analyzed using the quickestimation method described below, the macroscopic method (QATAR) described in subsequent sections, or commercially available microsimulation methods used to simulate airport curbside roadways.

Quick-Estimation Method The quick-estimation method is used to measure both the curbside utilization factor (i.e., the ratio between curbside demand and curbside capacity) and the maximum throughput rate for five-, four-, and three-lane curbside roadways. The level of service for a curbside roadway is defined as the worst result of these two measures. Estimates of the maximum flow rates (i.e., service flow rates) on curbside roadways at each level of service can be determined using the data provided in Table 5-2. These data were established from observations of curbside traffic flows conducted as part of this research project and analyses of curbside roadway traffic flows conducted using microsimulation of airport roadway traffic. Figure 5-2 depicts the relationship between curbside roadway traffic flow rates and utilization factors for five-, four- and three-lane curbside roadways. Since as used in Table 5-2, “capacity” varies depending on whether an airport operator allows vehicles to double or single park, the policy of the airport being analyzed should be reviewed. To establish the level of service for a given curbside demand and traffic volume, the data in Table 5-2 should be used as follows: 1. Calculate the curbside utilization factor. 2. Select the corresponding utilization factor for the curbside lane as shown in Table 5-2, rounding up to the next nearest value, and note the corresponding level of service. For example, for a four-lane curbside roadway with a calculated ratio of 0.6, the level of service is C. 3. Calculate the level of service for the through lanes by (1) selecting the maximum service flow rate row in the table corresponding to the appropriate number of lanes on the entire curbside roadway (include all curbside lanes and through lanes), and (2) comparing this rate to the volume of traffic on the curbside to calculate the volume/capacity ratio. For example, the roadway capacity is 2,680 vehicles per hour for a four-lane roadway with curbside lanes operating at LOS C. If this roadway were serving 2,500 vehicles per hour, it would have a v/c ratio of 2,500/2,680 or 0.93.


Source: Jacobs Consultancy, November 2009.

Figure 5-2. Curbside roadway capacity reduction curves.

4. Use Table 5-2 to determine the level of service that corresponds to the calculated v/c ratio for the through lanes. A v/c ratio of 0.93 corresponds to LOS E. 5. The level of service for the entire curbside roadway (system) is determined by the component—either the curbside lane or the through lanes—with the poorest level of service. Considering the above example, if the curbside utilization factor corresponds to LOS C and the peak hour traffic volume corresponds to LOS E, the level of service for the curbside roadway is LOS E. The maximum service flow rates shown in Table 5-2 apply to all vehicles on the curbside roadway, including those stopped in the curbside lane. These flow rates need not be adjusted for heavy vehicles or driver familiarity because they were developed from observations of traffic operations on airport curbside roadways.

Macroscopic Model—Quick Analysis Tool for Airport Roadways Developed through this research project QATAR allows airport planners and operators to determine the ability of a

curbside roadway to accommodate changes in traffic volumes, airline passenger activity, vehicle mix, curbside allocation plans, and curbside enforcement levels. QATAR also allows the user to observe how airport curbside roadway levels of service are expected to vary as these input factors change. Appendix G presents additional information on the methodology and mathematics used in QATAR. In the analysis procedure used in QATAR, it is assumed that (1) vehicles begin to double park and potentially triple park, if allowed, as the number of vehicles stopping in a zone approaches the zone’s capacity (or length), and (2) the capacity of the adjacent maneuver and travel lanes decreases as the number of double- and triple-parked vehicles increases. The propensity of arriving vehicles to double park (reflecting the percentage of occupied curbside spaces) can be modified by the QATAR user to reflect local conditions and policies. Using a multiserver (or multi-channel) queuing model, QATAR calculates • The number of vehicles stopping in each curbside zone to

drop off or pick up passengers. The number of spaces occupied simultaneously (assuming a 95% probability),


when compared to the number of available spaces, defines the level of service for the curbside lane. • The number of bypass vehicles proceeding to/from adjacent zones. The number of bypass vehicles, when compared to the capacity of the bypass lanes, defines the level of service for the bypass lanes. The capacity of the bypass lanes is determined by the number of travel lanes and the level of service of the curbside lane. As described previously, a reduction in curbside level of service (i.e., an increase in the amount of double and triple parking) causes a reduction in the capacity of the bypass lanes. • The peaking characteristics of the roadways, assuming that the volumes will not be exceeded 95% of the time during the analysis period. Traffic volumes on curbside roadways are

Figure 5-3. Example of QATAR input sheet.

not uniform throughout an hour-long period, or other analysis period, and peak periods of activity or microbursts of traffic occur frequently. Inputs Figure 5-3 presents an example of a QATAR input sheet (including the suggested default values for dwell times and vehicle stall lengths). As shown, the following information is required to use QATAR: • Curbside geometry—The physical characteristics of the

curbside, including length, number of lanes, and number of roadway lanes approaching the curbside area. If the user


• •

wishes to divide the curbside into zones, the length of each zone must be defined first. Hourly traffic volumes—The existing hourly volume of vehicles entering the curbside. If a future curbside condition is to be analyzed, the traffic volumes should be adjusted to reflect future growth. QATAR allows the user to apply a growth factor to existing traffic volumes. Through vs. curbside traffic volumes—The proportion of vehicles using the roadway that stop at the curbside. If the user has divided the curbside into zones, the proportion (or volume) of vehicles stopping in each zone is required. Vehicle mix—The mix (i.e., classification) of vehicles in the traffic stream entering the curbside (either the actual volume or the percent of vehicles by vehicle classification). If the user has divided the curbside into zones, the proportion (or volume) of vehicles by classification stopping in each zone is required, or the user can determine that the proportion is constant in each zone. Dwell times—The user can accept the default values in QATAR or enter vehicle dwell times by vehicle classification. Vehicle stall length—The user can accept the default values in QATAR or enter vehicle stall lengths by vehicle classification. Adjustment factors—The user can enter adjustment factors in QATAR to reflect the effect of pedestrian cross-

Figure 5-4. Example of QATAR output sheet.

walks, regional conditions/driver behavior, and a weighting/calibration factor. Outputs Figure 5-4 presents an example of a QATAR output sheet. As shown, QATAR yields the following outputs: • Level of service—A graphic depicting the levels of service for

the curbside areas and roadway through lanes in each zone. • Volume/capacity ratio—A tabular presentation of the

volume/capacity ratio for the through lanes in each zone. • Curbside utilization ratio—A tabular presentation of the

curbside utilization ratio for the curbside area in each zone. In some cases, the capacity of the roadway approaching the curbside may dictate the capacity of the curbside roadway segment. For example, the capacity of a five-lane curbside section with a two-lane approach roadway is governed by the ability of the approach roadway to deliver vehicles to the curbside. Limitations of the Analysis Tool QATAR is used to analyze the macroscopic flow of vehicles but not the operation of individual vehicles (as would a roadway traffic microsimulation model). As such, QATAR does not

54 • Replicate or analyze operations, such as individual vehicles

maneuvering into or out of curbside spaces, improperly parked vehicles, vehicle acceleration/deceleration characteristics, or how these characteristics vary by vehicle size or type. Analyze how roadway congestion or queues affect traffic operations in the zones located upstream of those being analyzed, or meter (i.e., restrict) the flow of vehicles into downstream zones. Represent pedestrians crossing a curbside roadway (properly or improperly) or vehicle delays caused by pedestrian activity other than to allow the user to estimate the approximate decrease in roadway capacity. Evaluate the potential capacity decreases of specific curbside geometries. Rather, a single, continuous, linear curbside roadway is assumed in the model. If the curbside roadway consists of one or more parallel curbside roadways, QATAR should be used to analyze each parallel curbside roadway separately. Consider any upstream or downstream congestion; rather, each zone is treated separately. In reality, a very congested section or loading zone could affect adjacent zones both upstream and downstream. The model does not capture any interaction between zones.

As such, QATAR produces an approximation of airport curbside roadway operations. If more detailed analyses are desired, the user is encouraged to use a microsimulation model capable of simulating airport curbside traffic operations. Interpreting the Results Certain vehicles (e.g., courtesy vehicles or door-to-door vans) may make multiple stops along the terminal curbside area, especially at large airports. Vehicles making multiple stops can be represented properly (using Option C—one of the available input sheet options in QATAR) because the total volumes of vehicles stopping in each zone need not equate to the total curbside roadway traffic. However, with Option C, QATAR requires percentages of vehicles to sum to 100% and vehicles making multiple stops may not be accurately represented, particularly if they account for a significant percentage of the total vehicles entering the roadway.

Use of Microsimulation Models Chapter 4 provides guidance on the use of microsimulation models for analysis of airport roadways. Based on research team reviews of commercially available microsimulation software packages commonly used (as of 2008), it was determined that all are capable of adequately modeling the noncurbside terminal area roadways and low-speed weaving and merging

maneuvers typically found on airports. However, not all software packages available at the time of the research team’s review were capable of modeling parking maneuvers or interactions between vehicles entering and exiting curbside parking spaces and adjacent through vehicles, or permitted vehicles to double or triple park. It is suggested that the capability of a software package be confirmed prior to considering its use in analyzing airport curbside roadway operations. The following guidance is provided on calibrating a microsimulation model for airport curbside roadways: • If double or triple parking is allowed, verify that the model

correctly predicts the average number of double and triple parkers during the peak hour (compare one-hour model simulation to one-hour field counts). • If queuing occurs on the existing curbside roadway, count the throughput in the through lanes and the number of vehicles processed per hour in the curbside lanes under such congested conditions. – Validate through-lane flow rates. Enter demands into the simulation model and verify that the maximum throughlane flow rate for the peak hour predicted by the model matches the field counts. Adjust mean headways in the model until the model through-lane volumes match the field counts. A difference of 5% to 10% between model through-lane volumes and field counts is acceptable. – Validate curbside processing capacity. Enter demands in the simulation model and compare the curbside processing rate to field counts. Adjust average dwell times in the model until the processing rate over the peak hour matches the field counts. This guidance is in addition to guidance published elsewhere (see FHWA guide on microsimulation model validation). Curbside Performance Measures for Analyses Performed Using Microsimulation The performance measures presented in Table 5-1 are intended to help select the appropriate curbside analysis method. When curbside roadways are analyzed using microsimulation methods, the performance measures presented in Table 5-2 can be used to compare curbside roadway alternatives in the context of level of service. The measures listed in Table 5-1 do not directly correspond to quantitative values equaling a specific level of service. For example, duration of queuing is a potentially useful measure in the context of comparing alternatives (e.g., if one curbside roadway alternative would result in 2 hours of queuing, while another would result in 1 hour of queuing), but the


magnitude of the queuing itself could be relatively minor, so reporting an LOS C result for one alternative and an LOS D result for the other could be misleading. Similarly, the queue length measure can provide an easy way to compare alternatives, but a relatively long queue could be a better condition than a relatively short queue if the rate at which vehicles are served at the curbside is relatively high for the alternative with the longer queue. Together, length of vehicle queues and average speed— two measures that are typically microsimulation software outputs—can provide a time in queue measure that can be used to compare and evaluate analyses of curbside roadway prepared using microsimulation models. Because of the wide range of motorist expectations regarding traffic conditions when they arrive at an airport curbside, a range of thresholds for time in queue between acceptable and unacceptable operations were identified, with unacceptable operations corresponding to the threshold between LOS E and LOS F. For the lowest of these thresholds, the time in queue was identified as 60 seconds. This time (60 seconds) is consistent with the LOS E/F threshold for unsignalized and signalized intersections and considered to be a reasonable lower threshold. For context, consider a small-hub airport, such as Billings Logan International Airport. Most of the time, there is no queue leading to this airport’s curbside, even during peak periods in bad weather. If a queue did develop such that motorists would have to be in the queue for 60 seconds, it would seem unacceptable in that context. For the upper bound of acceptable/unacceptable thresholds, a comment expressed in at least one focus group conducted for this research project—moving is acceptable, not moving is not acceptable—was used. From a motorist’s perspective, it would seem as if a queue were not moving if a person could walk faster than the vehicles were moving. Using an arbitrary queue length of one mile and brisk walking speeds

of 3 to 4 mph, the time spent in such a queue would be 20 and 15 minutes, respectively. The 20-minute time in queue appears to be a reasonable upper bound for a threshold between acceptable and unacceptable (anecdotal experience suggests that queues of this length likely occur at large airports somewhat regularly). This time in queue is not intended to represent the longest queue time during the busiest days of a year, when delays may be even greater. Also, higher values of time in queue could be used by airport operators who observe higher thresholds at their locations. Service thresholds corresponding to LOS A have also been defined. It is suggested that time in queue should not be zero, but should seem to a motorist as if it were nearly zero. A simple way to identify an LOS A value would be to take 10% of the LOS E/F value, which is close to the LOS A/B threshold for delay at signalized intersections defined in the HCM. For the LOS E/F threshold of 60 seconds, a time in queue of 6 seconds or less would correspond to LOS A— from a practical perspective, that would essentially mean no queue or perhaps one vehicle waiting, which is consistent with the original basis for this threshold. With an LOS E/F threshold set at 20 minutes, the LOS A time in queue would, therefore, be 120 seconds. Although 120 seconds in a queue seems high compared to, for example, a signalized intersection delay, for a motorist approaching a curbside anticipating a wait of up to 20 minutes, a 2-minute wait would seem remarkably short. Once the upper and lower level-of-service bounds are identified, the values for the other LOS values can be calculated using a straight-line projection between the two points. The results of these estimates, assumptions, and calculations are presented in Table 5-4. The information can also be presented in graph form, as shown on Figure 5-5. As noted, the values of the time in queue can easily be extrapolated upward from the 20-minute level to any value.

Table 5-4. Time spent in queue for levels of service.* Large medium-hub and large-hub Small-hub and smaller mediumairports (a) hub airports (a) Given maximum acceptable time spent in queue in seconds (a) Level of service







Maximum for LOS E Maximum for LOS D Maximum for LOS C Maximum for LOS B Maximum for LOS A

60 47 33 20 6

120 93 66 39 12

300 233 165 98 30

600 465 330 195 60

900 698 495 293 90

1,200 930 660 390 120

Notes: *Input data are to be taken from microsimulation modeling output. (a) Analyst must first select a value for the maximum acceptable time spent in queue for the subject airport. Then, using queue length and average speed outputs from the microsimulation model, the level of service can be identified.

56 1400

Time in Queue (sec)

1200 1000 Max for LOS E Max for LOS D Max for LOS C Max for LOS B Max for LOS A

800 600 400 200 0 60






Maximum Tolerable Time in Queue (sec) Note: Analyst must first select a value for the maximum acceptable time spent in queue for the subject airport. Then, using queue length and average speed outputs from the microsimulation model, the level of service can be identified.

Figure 5-5. Time spent in queue for levels of service, large medium-hub and large-hub airports (input data to be taken from microsimulation modeling output).



Improving Airport Curbside and Terminal Area Roadway Operations This chapter presents examples of commonly occurring airport curbside and roadway operational problems and potential improvement measures. Analyses and evaluations of airport curbside and terminal area roadways generally involve the following steps: 1. Identify the Problem(s)—Problem identification includes determining the causes of existing congestion, delays, imbalances in demand, and/or whether the existing (or proposed) roadway network can accommodate anticipated future requirements. 2. Document Goals and Objectives—Documenting the relevant goals and objectives of airport management (and other stakeholders) with respect to roadway operations is a key step in the analysis and evaluation process. The relevant objectives may include such broad categories as • Providing safe and secure operations for airport users; • Providing desired levels of customer service for airline passengers, visitors, employees, and other airport users; • Accommodating existing and future requirements; • Accommodating regional mobility needs/encouraging the use of public transportation; • Supporting regional air quality goals; • Supporting the airport’s ability to maintain or enhance airfield capacity by ensuring that changes to roadways and curbsides do not negatively affect airfield operations or capacities; and • Maintaining and enhancing the net revenues generated by the airport. Detailed descriptions and definitions of goals will allow the development of airport-specific objectives that can be used to compare and evaluate alternative improvement measures. 3. Identify and Develop Potential Improvements—The potential improvement measures described in this chapter can serve as a starting point for improvements that address

commonly occurring airport curbside and terminal area roadway operations. Tables 6-1 and 6-2 present commonly occurring problems and potential improvement measures for terminal area roadways and curbsides, respectively. These tables also indicate the relative benefits resulting from implementation of the improvement, although the actual benefits will vary significantly depending on the roadway configuration and nature of the problem at the specific airport. 4. Evaluate the Potential Improvements—The alternative analytical methods described in previous chapters can be used to quantify the changes expected to result from the potential improvements, to assess their advantages and disadvantages, and to identify the preferred improvement(s). 5. Reach Consensus on the Preferred Improvement—A key step in the implementation process is to build consensus supporting the selection and implementation of the preferred alternative. An evaluation process that quantifies the extent to which the potential improvement would support the stated goals and objectives of airport management (and other stakeholders) provides a foundation for achieving consensus. 6. Implement the Preferred Solution—This step could involve design and construction activities, operational improvements, or changes in airport management policies.

Typical Terminal Area Roadway Problems Operational and physical problems can adversely affect the ability of terminal area roadways to accommodate traffic efficiently and safely. In this section, 10 types of deficiencies that may occur in an airport environment are identified. These deficiencies typically can result in queues or delays; many airport roadways exhibit one or more of the deficiencies described in this section.


Table 6-1. Typical terminal area roadway problems and improvement measures.

Note: Relative success of an improvement measure may vary significantly depending upon factors unique to an individual airport.

Table 6-2. Typical curbside roadway problems and improvement measures.

Note: Relative success of an improvement measure may vary significantly depending upon factors unique to an individual airport.


Insufficient Roadway Capacity A roadway has insufficient capacity if, during the analysis period, the roadway operates at LOS D or worse (see Chapters 4 and 5 for definitions of levels of service). LOS D refers to congested roadways and is an unacceptable basis for planning airport roadways. Specific implications of insufficient roadway capacity include (1) congested roadway sections with queues extending to upstream roadways, (2) motorists experiencing frequent congestion and significant delays, and (3) a generally unsatisfactory airport experience.

Insufficient Merging Capacity Insufficient merging capacity results when a roadway does not provide sufficient capacity at points where two or more streams of traffic combine into a single stream. This deficiency results in roadway delays, congestion, and traffic queues extending back from the merge point. Merge segment capacity is determined by the volume of entering traffic, operating speeds, and number of lanes upstream and downstream.

Inadequate Weaving Distance Inadequate weaving distance results when a roadway does not provide sufficient length or travel lanes to accommodate the traffic volumes at the point where two or more streams of traffic traveling in the same direction cross or merge, causing vehicles to decelerate (or stop) while waiting for adequate gaps in the traffic stream. This deficiency results in (1) vehicle delays and queues, (2) higher accident rates, and (3) slower speeds and flow rates. Factors influencing required weaving distances are operating speeds, traffic volumes (merging, weaving, and flowing through the segment), and the number of lanes that vehicles must cross to complete the desired maneuver.

Lane Imbalance Lane imbalance results when a roadway segment, before a diverge or after a merge, contains two (or more) fewer lanes than the combined total number of lanes entering or exiting the segment. For example, at a point where two three-lane roadways merge, the downstream segment must consist of at least five lanes or a lane imbalance will result. At a point where a roadway diverges into two two-lane roadways, the upstream segment (prior to the diverge) must consist of at least three lanes. A lane imbalance can cause increased delays, sudden diverge or weave maneuvers, increases in the required roadway weaving distances (e.g., the number of lanes to be crossed), and higher accident rates. Proper lane balance helps reduce or avoid forced merges, weaves, and sudden maneuvers. For example, when a two-lane roadway splits or diverges into two roadways, lane balance can be achieved by providing a third lane prior to

the diverge point that allows motorists access to either of the two downstream roadways (e.g., an “either-or” lane) or by extending a lane downstream past the merge/diverge point and then dropping the lane using design guidelines appropriate for the roadway speed (e.g., taper distances).

Directional Information Overload Directional or wayfinding information overload occurs when more information (or decisions) is presented to a motorist than the motorist can read, comprehend, and react to in the available time (and distance). This overload causes drivers to weave suddenly, miss exits, make sudden or erroneous movements, or, in extreme cases, stop in the roadway (or on the shoulder) to read the signage. It is desirable to avoid presenting more than two decisions or more than four lines of text on each directional sign. If more than four lines of text must be used on one sign at an airport, it is necessary to prioritize the information and avoid using unfamiliar or inconsistent terms.

Insufficient Decision-Making Distance Insufficient decision-making distance is defined as an insufficient distance (or time) for motorists to read, comprehend, and react to information regarding a decision that must be made. This situation causes drivers to weave suddenly, miss exits, make wrong turns, or, in extreme cases, stop in the roadway to read the message or back up to the decision point. Factors contributing to providing the necessary decision-making distance include travel speed, message content, visibility of the decision point, and visibility of the directional signage.

Insufficient Queuing Space Queuing space represents the area required to accommodate vehicles stopped at an entrance (or exit) to a parking lot or other facility, traffic signal or turn lane, or vehicle inspection area so that vehicles in the queue do not interfere with traffic flow on the adjacent roadway or travel lanes. For example, a parking facility entrance should have sufficient space to accommodate vehicles queuing at the ticket issuing machines without having the queue extend onto the adjacent roadway. (See Figure 6-1.)

Unexpected Lane Drops/Inadequate Taper Lengths Unexpected lane drops and inadequate taper lengths (the distance required to introduce a new lane or drop an existing lane) result when a through lane unexpectedly ends and motorists are required to unexpectedly merge quickly into an adjacent lane. Required taper lengths, which vary according to


Figure 6-1. Insufficient queuing space at parking entry at Tulsa International Airport.

roadway operating speeds, are intended to allow sufficient distance for lane channelization and vehicle merging. Unexpected lane drops reduce roadway capacity and travel speeds, as motorists who become “trapped” in a lane are required to merge quickly (interfering with the flow of other vehicles in adjacent lanes).

Unexpected Transition from High-Speed to Low-Speed Roadway Environment Some motorists do not realize they need to slow down as they exit from a regional roadway (which may operate at more than 55 mph) and approach a terminal area roadway (which may operate at less than 30 mph) until they encounter a sharp curve at the entrance to the terminal or vehicles stopped in the roadway. This situation is particularly true at airports where a limited access highway, designed to freeway standards and capable of accommodating freeway speeds, connects the regional roadway network with the terminal area roadways (see Figure 6-2). Motorists may be provided few visual clues that the driving environment is changing and requires them to decelerate. Additionally, speed limit signs may get lost among the many other signs and distractions associated with roadways approaching an airport terminal. This transition is compounded by the reduction in roadway capacity that accompanies the reduction in speed: a three-lane access roadway operating at 55 mph (or more) has more capacity than a three-lane curbside roadway operating at 30 mph (or less). If the traffic volume on the access roadway is the same as that on the curbside roadway, it is necessary to provide additional travel lanes on the curbside roadway to compensate for the reduction in travel speed. Often, the volumes are not constant, as some traffic exits for non-terminal area destinations, such as parking and rental car facilities.

Missing Movements Missing movements are defined as a desired travel path or traffic movement that is not provided on an airport roadway

network. If a movement is missing, motorists may need to exit and re-enter the airport or travel extra distance. For example, at most major airports, motorists can proceed directly from the enplaning curbside to short-duration parking and from shortduration parking to the deplaning curbside without leaving the terminal area. The absence of roadway segments providing these direct movements increases traffic demand on the return-to-terminal roadways and vehicle miles of travel.

Potential Terminal Area Roadway Improvement Measures Potential improvements to terminal area roadway operations are presented in the following categories: • Physical improvements, • Operational measures, and • Airport policies.

Figure 6-2. Transition from high-speed to low-speed airport roadways at Baltimore/Washington International Thurgood Marshall Airport.


A general planning principle for the design and operation of airport roadways is to separate traffic generated by airline passengers and visitors from that generated by employees, air cargo, and services or deliveries. At airports with multiple entrances/exits, this can be accomplished by having one entry/exit serving airline passengers and the other serving nonpassenger traffic. At airports with one access road, this can be accomplished by having nonpassenger traffic exit the access roadway well in advance of the terminal area, and by providing a separate service roadway for these vehicles. Appendix B (Bibliography) lists selected references regarding the design and improvement of roadways and intersections and relevant design standards and guidelines relevant to airports. These references should be reviewed prior to implementing any roadway improvement, particularly those that require the design of new roadways or modification or reconfiguration of the layout of existing roadways.

Potential Physical Improvements to Enhance Roadway Operations Widen Roadways Additional roadway capacity can result from the following: • Constructing new lane(s). Additional lanes can be con-

structed if sufficient available right of way is clear (or if it can be cleared) of obstacles, such as existing or proposed buildings, underground utilities, aviation limit lines (where FAA restrictions govern acceptable land uses), or other fixed obstacles. Construction costs and schedules are a function of the roadway alignment, extent and type of construction, obstacles to be relocated (if any), need to maintain and protect other vehicular and pedestrian traffic during construction, and other factors. • Reconfiguring existing lanes. Additional lanes can be created by reducing the widths of existing roadway lanes to form additional lanes. For example, five lanes can be created on an existing four-lane roadway by reducing lane widths (e.g., from 13 feet or 12 feet to 11 feet or 10 feet) and by simultaneously reducing the width of, or converting, roadway shoulders or paved gutter strips into travel lanes. Unless existing drainage structures must be replaced or relocated, the cost of such reconfiguration is very low. • Lengthening tapers/correcting lane imbalances. Roadway construction is required to correct inadequate roadway tapers or lane imbalances. The length of a roadway taper depends on the posted speed. For example, a 250-foot-long taper is required on a 35 mph roadway to add (or end) a 12-foot-wide travel lane. Providing the required lane balance may require construction of a full lane (upstream or downstream) for a longer distance. Highway design guides

listed in Appendix B, including those published by AASHTO, provide additional information on this topic. • Adding exclusive left- or right-turn lanes. The capacity of at-grade intersections, particularly signalized intersections, can be improved by providing exclusive left-turn lanes (thereby eliminating conflicting traffic movements from a signal phase) or adding free-flow right-turn lanes. Reconfigure Roadways • Eliminating three-way decision points. It may be possible

to eliminate a three-way decision point without requiring major roadway reconstruction, by moving one of the decision points upstream and thereby converting the three-way decision point into two separate two-way decision points, which is preferable and easier for motorists. • Lengthening weaving area. It may be possible to improve an unacceptable weaving operation by closing one exit from the weaving area and directing traffic to a subsequent downstream exit leading to the same destination. For example, at Seattle-Tacoma International Airport, traffic operations on a return-to-terminal roadway were improved by directing recirculating traffic toward the airport exit and then to a path that leads back to the terminal, thereby extending the length of the weaving area. At Los Angeles International Airport, a movable gate arm is used to close a roadway to traffic on the busiest days of the year, requiring vehicles to follow a slightly longer path, but extending the length of the weaving area. Such improvements can be implemented for minimal cost (e.g., replacing a roadway directional sign and installing a barrier, if necessary). • Improving queuing space. Queuing space can be improved by either providing additional storage space or increasing flow rates through the point of constraint. For example at the entry or exit of a parking facility, queuing space can be increased (1) by relocating the gate arms at the entry or control booths at the exit plaza to provide additional storage space or (2) by increasing traffic flow rates at the control point by replacing the existing access control technology (e.g., replacing an existing ticket issuing machine with a card reader recognizing employee parking badges, or an automatic vehicle identification [AVI] transponder on commercial ground transportation vehicles). For example, with use of a credit card in/credit card out parking access control system, more vehicles can be processed per lane than with a cashier, and the need to print and issue parking tickets may be reduced or potentially eliminated. Improve Roadway Wayfinding Signs It may be possible to improve roadway guide signs by replacing complex, existing signs with simpler signs that can


be more easily understood by motorists. This can be accomplished by attempting to simplify and prioritize the message content, reviewing the text and font, and using standard phraseology where possible. The use of dynamic message signs may also be helpful in certain instances (e.g., parking controls and space availability). Construct and Operate Traffic Operations Center At airports with complex roadway networks and multiple parking facilities, it may be possible to improve traffic flows by constructing and operating a traffic operations center, similar to those in many large urban areas (see Figure 6-3). Using video cameras, traffic detectors, and other technologies, the traffic operations center allows airport staff to monitor airportwide traffic operations, direct airport traffic officers to congestion points, close or open parking facilities or roadways, change advisory signs, and perform other operations to improve the flow of traffic.

Potential Operational Measures to Enhance Roadway Operations Speed Reduction Measures It may be necessary to encourage motorists to decelerate as they approach the terminal area, particularly at airports where a limited access highway connects the regional roadway network with the terminal area roadways. Measures to encourage motorists to obey posted speed limits and slow down as they approach the terminal area include • Pavement texture. Contrasting pavement textures (e.g.,

brick, cobblestone, or gravel textures) can be cast into strips

of concrete pavement to create a warning signal (i.e., a rumble strip) for motorists as they approach a slow-speed area. It is possible to increase the frequency and volume of the warning signal by reducing the distance between successive strips. • Dynamic warning signs. Radar-activated speed limit signs can be installed to detect the speed of approaching vehicles and indicate to drivers how fast they are traveling. For vehicles exceeding the posted speed limit, the display could flash red. • Automatically activated pedestrian signals. Pedestrians crossing a roadway can automatically activate signals embedded in the roadway pavement. • Enforcement. Police enforcement measures and tools that are commonly and frequently used in non-airport environments can be used to enforce posted speeds, including parking police vehicles in a visible location. Transportation Demand Management When used in an urban or regional setting, transportation demand management (TDM) measures are used to discourage single-occupant, private vehicle trips by promoting ridesharing or the use of public transit, and to encourage motorists to drive outside peak hours. At airports, the most productive application of TDM is to encourage airport employees to share rides or use public transit to reduce the number of vehicle trips. For example, some airport operators and other employers have established work schedules that call for employees to work 9 out of every 10 days (e.g., take every other Friday off by working longer hours on other days). Other airport operators offer discounted transit passes or partially subsidize the commuting expenses of employees who agree to use transit and forego the use of parking facilities. Intelligent Transportation Systems

Figure 6-3. Transportation operations center at Frankfurt Airport.

A variety of intelligent transportation system (ITS) applications are available to encourage the efficient and safe use of transportation facilities. At airports these applications include pricing mechanisms (increasing parking costs), the use of AVI and global positioning system (GPS) technologies to monitor the location and number of trips made by commercial vehicles or shuttle buses, and a variety of systems for distributing traveler information to arriving motorists (e.g., airline schedules/delays and parking space availability). Traveler information can be distributed using the Internet, mobile telephones, highway advisory radios, flight information display systems (e.g., those located on deplaning curbsides or within cell phone lots), or dynamic signage presenting parking space availability information or warning overheight vehicles approaching areas with limited vertical clearance.


Potential Airport Policies to Enhance Roadway Operations Promote Transit Airport operators generally encourage the use of public transportation by supporting the construction and operation of rail transit services and by promoting the use of rubbertired public transit services. Specific actions used by airport operators to promote passenger (and employee) use of bus service include allocating the most convenient terminal curb space for bus stops, installing signs indicating bus schedules and expected waiting times, installing transit ticket vending machines at visible locations in the terminal building, providing employees with a guaranteed ride home in the event of emergencies, and subsidizing selected modes to reduce the cost to passengers. Encourage Remote Terminals with Express Bus Service An example of a remote terminal is an intercept parking lot that provides scheduled, express bus service for airport passengers and employees to and from the airport terminal. By encouraging the use of efficient access modes, these terminals reduce the number of vehicle trips on airport roadways. The operators of the airports serving Boston and Los Angeles subsidize remote terminals and express bus services (e.g., the Logan Express and Los Angeles Flyaway services) and similar privately operated services are provided at Kennedy, Newark Liberty, and San Francisco International Airports and LaGuardia Airport. (See Appendix B for additional information.) Encourage Consolidated Rental Car Buses or Courtesy Shuttles Consolidated rental car shuttle buses used at airports that have consolidated rental car centers replace the courtesy vehicles operated by individual rental car companies and thereby reduce the number of vehicle trips on airport roadways. The consolidated rental car shuttle buses can be operated by a rental car industry consortium or by the airport operator (using a third-party contractor) on behalf of the rental car companies. Some airport operators have successfully encouraged hotels/motels to operate consolidated courtesy vehicles or shuttle buses. Manage and Control Commercial Vehicle Operations Numerous measures are available to manage and control commercial ground transportation vehicle operations. These

measures, which primarily affect curbside roadway operations, but may also improve other roadway operations, are described in the remainder of this chapter.

Typical Curbside Roadway Problems Operational and physical problems can adversely affect the ability of airport curbside roadways to accommodate traffic safely and efficiently. Typical problems include those listed in this section.

Insufficient Curbside Roadway Capacity Insufficient curbside roadway capacity exists when curbside requirements (lengths) are greater than 1.3 times the usable curbside length and/or the through lanes on a curbside roadway operate at LOS C or worse. When curbside demand exceeds available capacity, motorists experience significant delays and queues, as evidenced by high levels of double and triple parking throughout the entire curbside, which, in turn, reduces the capacity and travel speeds of the curbside roadway through lanes. As noted previously, curbside roadways must provide both adequate curbside length (stopping space) as well as adequate throughput capacities. Any deficiencies in one area will adversely affect the other. Factors that contribute to a lack of curbside roadway capacity are described in the following paragraphs.

Imbalances in Demand Imbalances in curbside demand occur when the total length of curbside space available is sufficient to accommodate curbside demand, but most of the demand occurs at, and overloads the capacity of, one segment of the total curbside area. For example, if one or more airlines on one concourse serve most of the peak-hour airline passenger activity, then curbside traffic will be concentrated at the doors leading to the portions of the terminal building occupied by these airlines, leaving the remainder of the curbside areas empty or underutilized. Generally, it is not feasible to relocate the assigned airline ticket counter or baggage claim area locations solely to balance curbside demand.

Insufficient Number of Travel Lanes A curbside roadway that does not provide sufficient capacity to accommodate existing or future requirements at LOS C or better typically has an insufficient number of travel lanes. Generally, curbside roadways with four lanes or more provide sufficient capacity because two travel lanes remain available even when double parking occurs. Congestion and delays may occur frequently on curbside roadways having three lanes or


fewer as any double parking severely restricts through traffic. Similar restrictions also occur when vehicles are allowed to stop on the inner and outer lanes of a four-lane curbside, leaving only the two center lanes for through traffic.

Pedestrian Crosswalks and Pedestrian Activity Pedestrians crossing a curbside roadway restrict the volumes of through traffic that can be accommodated. Delays caused by crosswalks are related to the volume of pedestrians walking across a curbside roadway, the proportion of time that pedestrians occupy a crosswalk (properly or improperly), and the number of crosswalks located at curbside. Traffic flows and safety also can be adversely affected by pedestrians stepping into the roadway to avoid columns or other obstacles, hail vehicles, or board/alight from a vehicle stopped in a through lane.

Driveways Serving Adjacent Land Uses Driveways serving adjacent land uses (e.g., parking lots or rental car ready/return areas) may impede the flow of curbside traffic when vehicles in the lane farthest from the terminal decelerate (or accelerate) as they enter (or exit) the driveways serving the adjacent land uses. Vehicle queues formed at the entrances to these land uses may extend back onto the curbside roadways.

Insufficient Curb Length Insufficient curb lengths result from curbside demand that is greater than 1.3 times the usable curbside length, which also occurs when there is significant double parking.

Inefficient Allocation of Curb Space Inefficient allocation of curb space results where the total available space is adequate to accommodate demand, but the available space has been divided into (or allocated among) many categories of ground transportation services such that some categories are allocated more curb space than required while others are not allocated enough. This situation may occur when curb space is allocated to vehicles that rarely serve the airport (e.g., charter buses), demands have changed as a result of the introduction of new services, or the space has been broken into small segments that do not correspond to the operational or maneuverability needs of the assigned class of ground transportation service. Similarly, inefficient allocation of curb space results when the amount of curb associated with a specific airline does not match the relative share of passenger traffic served by that airline.

Unusable Curbside Roadway Geometry Unusable curbside roadway geometries exist when vehicles cannot stop to load or unload passengers because of the curved alignment of the roadway, narrow sidewalks, or other physical obstructions. Many terminals have curved curbside roadways, but generally the radii of these roads are very large and motorists do not perceive that they have stopped along a curvilinear section. However, some curbside roadways have small radii or tight curves that hinder a motorist’s ability to park parallel to the sidewalk or to enter or exit this space. Motorists may be unable to park adjacent to curbsides having narrow sidewalks (e.g., the ends of island curbside areas) or columns (or other obstacles) adjacent to the roadways. Large bollards, which are sometimes placed on terminal building sidewalks to protect pedestrians and the terminal building from vehicles that may accidentally jump the curb, may interfere with the ability of motorists to open/close their doors or enter/exit their vehicles. Narrow sidewalks also may force pedestrians to step into the roadway (with their baggage) to bypass columns, queues of passengers formed at skycap positions, benches, or other obstacles.

Excessive Dwell Times Excessive dwell times result when vehicles (either private or commercial) are allowed to remain at the curbside when not actively loading or unloading passengers. In the case of some commercial vehicle providers, excessive dwell times are permitted by airport rules and regulations. Excessive dwell times may reflect insufficient police presence or visibility, or permissive airport policies and may occur even if the dwell times of most vehicles are within reasonable limits and fewer than 10% of vehicles remain at the curbside for excessive periods.

Potential Curbside Roadway Improvement Measures Potential curbside roadway improvements to enhance operations are presented for the following categories: • Physical improvements, • Operational measures, and • Policy measures.

Physical Improvements to Enhance Curbside Operations Widen Curbside Roadways Additional curbside roadway capacity can be provided by the following:

65 • Adding lanes to an existing curbside roadway. Widening a

roadway from four lanes to five lanes, for example, can increase through-lane capacity and allow the roadway to better accommodate double- or triple-parked vehicles as well as the interruption to through traffic caused by vehicles entering and exiting curbside lanes. • Constructing new curbside roadway(s) and center island curbside area. Constructing a second (or third) roadway parallel to an existing curbside roadway can increase (almost double) the capacity of a curbside area. The amount of additional capacity realized from such an improvement is a function of the resulting effective length and the allocation of space. Private vehicle motorists are reluctant to use curbsides perceived as being less convenient. Customer service and the attractiveness of a curbside waiting area can be enhanced by providing weather protection for passengers at curbside areas not located immediately adjacent to a terminal building or under a building canopy. Similarly, shelters with benches can improve the service levels for customers waiting for scheduled transportation services or courtesy vehicles. • Constructing a new bypass roadway. At airports with multiple terminals, construction of a bypass roadway can reduce the volume of through traffic on a curbside roadway and increase the level of service. Lengthen Curbside Roadway It may be possible to extend the length of a curbside area past the terminal building façade if conveniently located doorways are available to serve motorists using these extensions. Commercial vehicles can be assigned to extended curbside areas, particularly infrequent users of the airport, such as charter vehicles. Private vehicle motorists prefer to stop in front of the terminal building and are unlikely to use extended curbside areas unless they are perceived as convenient.

building because passenger terminal building layouts dictate curbside roadway designs (rather than vice versa). A roadway that does not match a building’s floor elevation would require separate vertical circulation elements to allow passengers to transition between the terminal building and roadway. Consequently, the decision to construct a second-level curbside roadway, for example, is driven by the design of a new terminal building or planned expansion of an existing terminal building. Remove Pedestrian Crosswalks Additional capacity can result from the following: • Merging crosswalks. Roadway traffic operations can be

improved by merging crosswalks to reduce the number of locations where vehicular traffic flow is interrupted. Such changes may reduce the level of service for some pedestrians, because they would be required to walk farther. In the extreme case, it may be necessary to install fences or barriers to discourage jaywalking, and potentially to use traffic signals or traffic control officers to control pedestrian traffic. • Relocating pedestrian traffic. Roadway traffic operations can be improved and pedestrian levels of safety enhanced by constructing pedestrian bridges above, or tunnels beneath, a curbside roadway and removing at-grade pedestrian crosswalks (see Figure 6-4). Since the path would require pedestrians to change grades (while transporting baggage), it would be necessary to make the new path more attractive than an alternative at-grade path, or to construct fences or other barriers to discourage passengers from continuing to cross the curbside roadway at grade. • Controlling pedestrian activity. Pedestrians crossing a roadway can automatically activate signals embedded in

Construct Additional Curbside Level At airports with a single-level curbside roadway serving a multilevel terminal building, additional capacity can be provided by constructing a new elevated curbside roadway. For example, in 1984, a second-level curbside roadway was constructed above the then single-level curbside roadway at Los Angeles International Airport. A second-level curbside roadway also was added at Hartford’s Bradley International Airport. Such a capacity enhancement requires that the terminal building either have multiple levels or be modified concurrently with the roadway expansion. Generally, it is considered impractical to add capacity by constructing a two-level curbside to serve a single-level building or a three-level curbside to serve a two-level terminal

Figure 6-4. Elevated pedestrian bridge at Los Angeles International Airport.


the roadway pavement to improve pedestrian safety and control pedestrian and vehicular traffic flows.

curbside areas within parking garages allocated for commercial ground transportation or private vehicles, or space adjacent to the garage that is not directly accessible from a terminal building. These areas are particularly attractive when grade-separated pedestrian access is provided between the terminal and the parking structure. Examples include – A curbside roadway located within a garage allocated to commercial vehicles (e.g., Seattle-Tacoma International Airport); – A commercial vehicle passenger pickup area/curbside space located at a close-in parking structure away from the terminal (e.g., Indianapolis International Airport); and – A curbside roadway located within a parking garage allocated to private vehicles (e.g., Lambert-St. Louis International, Salt Lake City International, and LaGuardia) (see Figure 6-5). • Commercial vehicle courtyards. A commercial vehicle courtyard is a parking area adjacent to or near the terminal building reserved for use by commercial vehicles picking up or dropping off airline passengers. These areas are referred to by various terms, such as “ground transportation center”

or “intermodal center.” Courtyards and dedicated curbside roadways can augment the capacity of a curbside area (or relieve congestion) by providing additional passenger pickup (or drop-off) areas. These areas can benefit commercial vehicle operations as the operators need not maneuver through private vehicle traffic to enter and exit their assigned spaces, and are allowed longer dwell times in these areas. Commercial vehicle courtyards are provided at the airports serving Atlanta, Fort Lauderdale, Newark, San Francisco, and Tampa. The airports serving Denver, Nashville, Orlando, San Francisco, Toronto, and Washington, D.C. (Dulles) have three-level curbside areas (see Figure 6-6) with one entire level reserved for commercial vehicle use. Although these commercial vehicle areas operate in a manner similar to courtyards, they are not considered potential curbside improvement measures because, as noted earlier, their implementation requires the appropriate terminal building configuration. • Remote curbsides. At Chicago O’Hare International Airport, commercial vehicles pick up and drop off passengers on a roadway located between the on-airport hotel and the central parking garage. Underground tunnels link this site (the Transportation Center) to the terminal buildings. An enclosed and heated/air conditioned passenger waiting area with seating is provided in the parking garage adjacent to the Transportation Center. At San Francisco International Airport, a supplemental remote curbside is available to serve the drivers of private vehicles meeting arriving passengers. This supplemental curbside is located adjacent to a remotely located Consolidated Rental Car Facility and automated people mover station. The station, intended primarily for use by rental car customers, allows passengers to easily travel to the supplemental remote curbside.

Figure 6-5. Supplemental curbside inside parking structure at Salt Lake City International Airport.

Figure 6-6. Three-level curbside at San Francisco International Airport.

Provide Alternative Passenger Pickup/Drop-Off Areas Alternative or supplemental curb space can be developed to augment the capacity of the areas adjacent to the terminal building. Examples of alternative passenger pickup or dropoff areas include • Curb space within a parking garage. Several airports have


Operational Measures to Enhance Curbside Capacity Reduce Curbside Requirements The following measures are intended to enhance curbside capacity for certain vehicle modes by reducing the amount of curbside required by other vehicles. • Restrict curbside use to authorized vehicles. The use of

curbside areas (or portions of curbside areas) can be restricted to authorized commercial ground transportation vehicles. Numerous airport operators limit the use of commercial vehicle lanes by posting “authorized vehicles only” signs at the entrance to these lanes, or by installing gate arms activated by AVI transponders, proximity cards, or other devices. Unauthorized commercial vehicles (e.g., those without airport permits or AVI tags) cannot gain access to these areas. As noted in subsequent paragraphs, commercial vehicles may be required to abide by other airport regulations limiting their use of curbside roadway areas. • Develop cell phone lot. A cell phone lot (also referred to as a park and call lot) is a free parking area located away from the terminal where a motorist picking up a deplaning passenger can wait until the passenger has gotten off the plane, claimed baggage, arrived at the curbside, and called the motorist to indicate their arrival at the curb. Cell phone lots enable motorists to use curbside areas efficiently because (1) the airline passengers can tell the drivers exactly where they are (or will be) located at the curb, (2) if the curbside area is congested, the passenger and motorist can arrange an alternate pickup location (e.g., a different curbside area), and (3) the motorist will avoid being forced to leave the terminal area and possibly recirculate multiple times (e.g., if the airline passenger was not ready when the motorist first arrived at the curbside). The operators of some airports (e.g., those serving Phoenix and Salt Lake City) have placed outdoor flight information display monitors or dynamic signs presenting this information within cell phone lots to assist waiting drivers (see Figure 6-7). At other airports (e.g., Tampa International Airport), such signs have been installed on the deplaning level curbside to aid waiting motorists and encourage them to exit the curbside when flights are delayed (see Figure 6-8). Several airport operators have or are developing on-airport convenience stores or retail centers where the parking area can be used as a cell phone lot (e.g., Denver International Airport). • Provide attractive or free short-term parking. Motorists can be encouraged to park in a conveniently located shortterm parking lot if they are confident that they can easily find an empty, reasonably priced space. Encouraging motorists to park while accompanying an airline passenger to/from the terminal rather than using the curbside areas reduces

Figure 6-7. Flight information display system at cell phone lot at Salt Lake City International Airport.

curbside requirements. The extent of the reduced demand is a function of the proportion of motorists attracted to parking who would not have otherwise parked. To encourage the use of short-term parking, some airport operators offer free parking for up to 30 minutes. However, analyses of beforeand-after data at Seattle-Tacoma International Airport indicate that 30 minutes of free parking had a negligible effect on curbside requirements. • Encourage the use of public transit. As described in the previous section on Potential Airport Policies to Enhance Roadway Operations, by encouraging airline passengers to use public transit, airport operators can reduce airport roadway and curbside traffic. Numerous methods are available to encourage the use of public transit, including allocating preferential curb space to publicly or privately operated public transit services.

Figure 6-8. Flight information display system at deplaning curbside at Tampa International Airport.


Reduce the Speed of Curbside Roadway Traffic

• Modifying the amount of space allocated. The amount of

Measures to encourage motorists on curbside roadways to operate safely or to slow down and watch for pedestrians crossing the roadway include the following (in addition to those described above under roadway operations): • Use speed humps and speed platforms or tables. These

devices are forms of raised roadway pavements placed across a travel lane to force motorists to slow down. These devices are generally used on roadways operating at less than 25 mph. The key differences between these devices are their length and the amount of speed reduction achieved. Speed humps are 6 to 12 inches high, and about 4 to 6 feet long with a gradual sloping approach. Speed platforms or tables are flat-topped speed humps that are long enough for an entire vehicle to rest on top, and that can function as raised pedestrian crosswalks. Speed platforms can reduce traffic speeds, help indicate the locations of crosswalks to motorists, and minimize grade changes for disabled pedestrians crossing the curbside roadway. It is necessary to confirm that adequate vertical clearance will be possible prior to installing a speed hump or platform on the lower level(s) of a multilevel roadway. The use of speed bumps—raised devices 2 feet long or shorter with abrupt slopes—is strongly discouraged. • Roadway width restrictions. Narrower lanes or physical constraints on roadway widths can encourage motorists to drive slowly. Curbside roadway widths can be constrained by reducing the number of roadway lanes, or lane widths at crosswalks, the ends of median islands, and other locations. Improve Curbside Enforcement Police enforcement procedures commonly used elsewhere can be used to enforce curbside traffic operations at airports. Enforcement of dwell times and unattended vehicle prohibitions typically receive more attention than speeding on curbside roadways. Some airport operators contract with a tow truck operator parked at, or near, the curbside entrance to discourage motorists from leaving their vehicles unattended, remaining at the curbsides too long, or engaging in other improper behavior. Some airport operators employ traffic control officers (TCOs) rather than licensed law enforcement officers (LEOs) for curbside operations because of their effectiveness (TCOs can focus entirely on traffic control and are not dispatched to other assignments) and cost (TCO wages are typically lower than those of LEOs); thus, an airport operator can hire more TCOs than LEOs. Revise Curbside Allocation The space allocated for individual categories of ground transportation services can be revised by

space allocated to each category of ground transportation service (including private vehicles) can be increased or decreased to respond to changes in airline passenger activity or curbside requirements, introduction of new transportation services, or new airport policies. Moving assigned spaces. The assigned space can be relocated to a better (or worse) location near a major exit door serving a major airline or to an inner curbside from an outer curbside. Combining or separating spaces. The curb space allocated to different categories of ground transportation can be merged or separated. For example, all courtesy vehicles can be required to use a common curbside area rather than separate space being allocated for the courtesy vehicles serving hotels, parking lots, and rental car companies (or these services can be separated). Requiring single-stop operations. Improved utilization of available curb space can result from requiring commercial vehicle operators to drop off and pick up passengers at the same location (e.g., having courtesy vehicles drop off and pick up their customers on the upper level). This requirement reduces the number of stops and amount of spaces required by these vehicles. Requiring commercial vehicles or public transit to drop off and pick up customers at a single location also reduces customer service by requiring more level changes and longer walks. Using off-peak areas. Improved utilization of existing curb space can result from requiring commercial vehicle operators to drop off and pick up passengers at underutilized areas of the terminal building. An example would be requiring commercial vehicles to drop off customers at the baggage claim area during the enplaning peak hour or to pick up passengers at the ticketing area during the deplaning peak hour.

Modify Commercial Ground Transportation Vehicle Operations Airport operators can establish ground transportation rules and regulations that govern how, where, and when a ground transportation vehicle operator is allowed to use airport roadways. The following section provides additional information.

Potential Airport Policies to Improve Curbside Operations Airport operators can require commercial vehicle operators picking up airline passengers to abide by airport rules and regulations governing (1) the roadways each operator may use, (2) where commercial vehicle operators are allowed to stop on the airport roadways to drop off or pick up passen-


gers, (3) the maximum dwell times permitted, (4) the speed limits and other restrictions they must obey, and (5) the fees they must pay to operate on the airport. Examples of these policies and regulations are provided below. Airport operators may require the operators of commercial ground transportation services to pay a variety of fees to recover costs or manage demand. These fees include those charged on an annual or monthly basis per company or per vehicle, and cost-recovery fees typically calculated based on the ground transportation operator’s volume of vehicle trips or volume of airport-related business. Demand management fees include fees penalizing operators that remain in the curb-

side area in excess of a specified maximum dwell time, exceed a daily or monthly limit on the number of courtesy vehicle trips, and violate established minimum time intervals between successive courtesy vehicles they control. Airport operators may use these fees to improve curbside traffic operations, discourage unnecessary trips—including those made by an operator seeking to advertise its product or service (i.e., operating moving billboards rather than transporting customers)—reduce vehicle emissions and improve air quality by encouraging the use of alternative fuel vehicles or consolidated shuttle vehicles through the use of discounted fees, or achieve other objectives of the airport operator.



Appendix A, Glossary, is provided herein, and Appendices B through G, as submitted by the research agency, are available at Their titles are as follows: Appendix B Appendix C Appendix D Appendix E Appendix F Appendix G

Bibliography Summary of Terminal Area Roadway Traffic Volume Surveys Summary of Curbside Roadway Characteristic Surveys Summary of Focus Group Surveys A Reproduction of Portions of TRB Circular 212 Overview of QATAR Curbside Analysis Methodology




Adjusted flow rates—The maximum rate of flow adjusted for traffic conditions, traffic composition, roadway geometry, and other factors. Air taxi—A for-hire passenger or cargo aircraft that operates on an unscheduled basis. Airfield licenses—Licenses or permits required to operate a ground transportation vehicle on an airfield at major airports. Airport curbside—The one-way roadway located immediately in front of the terminal building where vehicles stop to pick up and drop off airline passengers and their baggage. Automatic traffic recorder (ATR)—Equipment, often portable, that records the volumes of traffic crossing a pneumatic tube or detector. Automatic vehicle identification (AVI)—Radio frequency identification equipment (i.e., vehicle-mounted tags or transponders) commonly used on roadways and bridges to collect tolls. Auxiliary lane—A supplementary lane intended to facilitate weaving or merging vehicle movements between a roadway entry and exit. Bypass lanes—Curbside roadway lanes intended for use by vehicles bypassing or not stopping at a curbside section or zone. Bypass vehicles—Vehicles traveling past, but not stopping at, a curbside section or zone, including vehicles recirculating past the curbside, vehicles traveling to/from adjacent curbside zones, or service/delivery vehicles using the curbside roadway. Cell phone lots—Free parking lots, typically located away from the terminal area, provided for use by motorists waiting to pick up deplaned passengers. Also referred to as “call-andwait” or “park-and-call” lots.

Commercial vehicles—Vehicles transporting airline passengers and visitors, including taxicabs, limousines, courtesy vehicles, buses, and vans, driven by professional drivers for which vehicle passengers pay a fee or for which the transportation is incidental to the service provided (e.g., a hotel courtesy vehicle). Cost path—A person’s perceived cost that would be incurred while traveling along a defined path or route, typically including the value of time. Courtesy vehicles—Door-to-door, shared-ride transportation provided by the operators of hotels/motels, rental car companies, parking lots, and other services solely for their customers. Critical movement analysis—An analysis conducted to calculate the lanes or movements requiring the most “green time” at a signalized intersection and, therefore, a method of estimating the intersection volume to capacity (v/c) ratio. Critical volumes—The volume or combination of volumes (e.g., conflicting movements) that produces the highest demand for an intersection lane or signal phase. Curbside geometry—The horizontal and vertical alignment features of a curbside roadway, including lane widths, grades, curvature, and crosswalks. Customs and Border Protection (CPB)—The U.S. government agency responsible for, among other duties, inspection of international arriving passengers and goods to collect import duties and prevent the import of illegal goods. Decision-making distance—The physical distance between successive decision points. Decision point—The physical location where a driver must select between alternative paths or roadways. Deplaned passengers—Passengers that alighted from an aircraft at an airport, including both connecting and terminating airline passengers.


Discount factor—An adjustment applied to reduce the effective capacity of curbsides with an unusual configuration, location, or operation. Double parking—A condition in which two or more vehicles are parallel parked or stopped adjacent to one another along the curbside roadway. Driver population factor—A factor applied to roadway capacities to reflect driver behavior and operating characteristics, including familiarity with roadways, intersections, and traffic patterns. Electronic ticketing kiosk—A self-serve machine used by airline passengers to print boarding passes and other documents. Enplaned passengers—Passengers who boarded an aircraft at an airport, including both connecting and originating airline passengers. Fixed-base operator (FBO)—An aviation business that serves general aviation aircraft owners and operators, including fueling, catering, aircraft maintenance, and storage. Flattening the peak—A reduction in the proportion of demand occurring in a 15-minute or hourly interval as a result of demand management, changes in schedules, demand approaching capacity, or other reasons. Free-flow speed—The mean speed of traffic under very light flow conditions. General aviation—All flights (or aircraft operations) other than scheduled/commercial or military flights. Gore—The triangular area between two roadways at the point they diverge or merge. Green time—The duration, in seconds, of the green indication for a given movement at a signalized intersection. Growth factor—A factor applied to passenger or traffic volumes, for example, to adjust for anticipated future growth. Heavy vehicle—A vehicle with more than four wheels touching the pavement during normal operation. Heavy vehicle factor—A factor applied to roadway capacities to reflect the proportion of heavy vehicles in the traffic stream. Highway capacity analysis procedures—Analytical procedures conducted using the procedures described in the Highway Capacity Manual. Highway Capacity Manual (HCM)—The Highway Capacity Manual published by the Transportation Research Board, National Research Council, 2000 (and subsequent editions, including the draft 2010 HCM).

Immigration and Customs Enforcement (ICE)—The U.S. government agency responsible for, among other duties, inspection of international arriving passengers and crew prior to their entering the country. Intelligent transportation system (ITS)—Information and communication technologies applied to transportation infrastructure and vehicles to improve operations, safety, and efficiency. Intersection Capacity Utilization (ICU) method—As used in this Guide, a quick-estimation method for analyzing intersections using the critical movement analysis. Lag time—The length of time after a flight’s scheduled arrival time that a passenger arrives at the airport curbside. Landside circulation system—The airport roadway network providing for inbound and outbound traffic and the internal circulation of traffic between airport land uses. Lane balance—A situation that exists when the number of lanes entering a roadway is equal to the number of lanes exiting the roadway. Lane geometry—The horizontal and vertical alignment features of a roadway or roadway lane, including lane widths, grades, lengths, curvatures, tapers, and other physical features. Lateness distribution—The distribution of passengers leaving an airport after the scheduled arrival time of their aircraft (i.e., a distribution of passenger lag times). Lead time—As used in this Guide, the length of time in advance of a flight’s scheduled departure time that a passenger arrives at the airport curbside. Macroscopic models—Models or analytical procedures used to consider the flow of vehicle streams (or other objects) rather than the flow of individual vehicles. Manual of Uniform Traffic Control Devices (MUTCD)— The principal standard governing the application, design, and placement of traffic control devices, published by FHWA. See Maximum service flow—A maximum flow rate at which vehicles can traverse a point or short segment during a specified time period at a given level of service. Merging capacity—Maximum flow rate at a merge point. Metropolitan planning organization (MPO)—A policymaking organization responsible for planning, analysis, and development of multimodal transportation facilities in a region or community.


Microsimulation models—Models or analytical procedures used to simulate the operation of individual vehicles (or other objects) on simulated roadway (or other) networks.

Terminal area roadways—The roadways serving the terminal building and surrounding areas, including access, curbside, and circulation roadways.

Mixed-flow traffic volumes—The numbers of vehicles in a traffic flow consisting of multiple vehicle types.

Through vehicles—As used in this Guide, vehicles bypassing the curbside area or zone. Also see “Bypass vehicles.”

Operational characteristics—Traffic flow characteristics, including speed, density, vehicle mix, and volumes.

Time path—A person’s perceived time incurred while traveling along a defined path or route, including time in motion, delays caused by congestion, and waiting time.

Passenger car equivalent (pce)—The number of passenger cars displaced by a single heavy vehicle of a particular type under specified roadway, traffic, and control conditions. Passenger load factor—A measure of available aircraft seats that are occupied. Peak hour—The peak hour is the busiest hour of the year, month, or day. It is suggested that the “design hour,” rather than the peak hour, be used for planning and evaluation of airport roadways, and that the design hour be a typical busy hour on the peak day of the week during the peak month. Peak-hour factor—The relationship between the hourly traffic volume in the peak hour and the maximum rate of flow within some portion of the hour. As used most commonly, this factor refers to the ratio of the hourly volume to the maximum 15-minute flow rate expanded to an hourly volume. Performance capabilities—As used in this Guide, the capabilities of an individual vehicle or group of vehicles, including acceleration, maneuverability, and turning radii. Poisson distribution—A discrete probability distribution that expresses the probability of a number of events occurring in a fixed period of time.

Traffic controls—Devices directing vehicular and pedestrian traffic flows, particularly at conflict areas, including signals, signs, and pavement markings. Transborder flight—As used in this Guide, scheduled flights between the United States and Canada whose passengers have typically been pre-cleared by border controls. Transportation demand management (TDM)—The application of policies and strategies to reduce travel demand or redistribute this demand in space or time. Trip generation rate—The number of vehicle or person trips generated by a household, zone, land use, or other facility generally during a daily or peak period. Triple parking—A situation in which three or more adjacent vehicles are parallel parked or stopped along the curbside roadway. Weaving area—The roadway segment in which two or more traffic streams traveling in the same general direction along a significant length of roadway cross one another without the aid of traffic control devices.

Remote curbside—A curbside located outside of the immediate area of the passenger terminal building, such as in a parking structure, surface lot, or multimodal facility.

Weaving distance—The distance from a point on the merge gore at which the right edge of the freeway shoulder lane and the left edge of the merging lane are 2 feet apart to a point on the diverge gore at which the edges are 12 feet apart.

Rental car ready/return—The parking or storage area(s) to which rental car customers return rented vehicles or pick up rental vehicles.

Weaving intensity factor—A measure of the influence of weaving activity on the average speed of both weaving and nonweaving vehicles.

Signal phasing—The part of a traffic control signal time cycle allocated to any traffic movement given the right of way.

Vehicle mix—The proportion of each type of vehicle (i.e., bus, car, van, truck) in a traffic stream.

Skycap—A porter employed by an airline or airport operator to provide baggage drop service to passengers.

Vehicle occupancy—The number of passengers (including the driver) in a vehicle.

Steady-state performance—The traffic flow rates occurring on a roadway or intersection when the traffic stream is not disrupted or interrupted.

Vehicle stall length—As used in this Guide, the length of curb space occupied by a stopped vehicle, including the distance required to maneuver into and out of the space.


American Association of Airport Executives American Association of State Highway Officials American Association of State Highway and Transportation Officials Airports Council International–North America Airport Cooperative Research Program Americans with Disabilities Act American Public Transportation Association American Society of Civil Engineers American Society of Mechanical Engineers American Society for Testing and Materials Air Transport Association American Trucking Associations Community Transportation Association of America Commercial Truck and Bus Safety Synthesis Program Department of Homeland Security Department of Energy Environmental Protection Agency Federal Aviation Administration Federal Highway Administration Federal Motor Carrier Safety Administration Federal Railroad Administration Federal Transit Administration Hazardous Materials Cooperative Research Program Institute of Electrical and Electronics Engineers Intermodal Surface Transportation Efficiency Act of 1991 Institute of Transportation Engineers National Aeronautics and Space Administration National Association of State Aviation Officials National Cooperative Freight Research Program National Cooperative Highway Research Program National Highway Traffic Safety Administration National Transportation Safety Board Pipeline and Hazardous Materials Safety Administration Research and Innovative Technology Administration Society of Automotive Engineers Safe, Accountable, Flexible, Efficient Transportation Equity Act: A Legacy for Users (2005) Transit Cooperative Research Program Transportation Equity Act for the 21st Century (1998) Transportation Research Board Transportation Security Administration United States Department of Transportation


ACRP Report 40 Airport Curbside and Terminal Area Roadway Operations Appendix B BIBLIOGRAPHY This appendix presents an annotated bibliography of documents reviewed during the literature search for this research project on airport curbside and terminal area roadway operations, with an emphasis on those documents that describe analytical procedures and performance measures. The documents are organized under the following topics: • • • • • •

General landside access Performance measures Terminal area roadways Analytical tools Simulation models Curbside operations

GENERAL LANDSIDE ACCESS The following documents provide a general overview of airports including their planning, design, and operations. They describe the major components of an airport landside sector, and how they interrelate with each other and with the airside sector. These documents provide a foundation for the material contained in subsequent sections of this bibliography as they explain the purpose and function of the airport landside sector, the general configuration and operations of terminal curbsides, and the types and functions of terminal-area roadways. Textbooks 1. Ashford, Norman and Paul H. Wright, Airport Engineering, Third Edition. John Wiley & Sons, 1992. References curbside analysis procedures published by Cherwony and Zabawski (see reference #20 under Analytical Tools). 2. Ashford, Norman, H.P. Martin Stanton' and Clifton A. Moore, Airport Operations, Second Edition. McGraw-Hill, 1997. A basic reference on all aspects of airport operations. Airport access chapter presents nomographs for estimating curbside lengths in terms of passenger volumes.

B-2 3. De Neufville, Richard and Amedeo Odoni. Airport Systems: Planning, Design, and Management McGraw-Hill, October 2002. The most recent textbook on airport systems planning, design, and management. Describes full range of computer-based tools and methodology. Terminal buildings chapter provides overview of curbside operation, configurations, and a formula for approximating curbside requirements. 4. Hart, Walter. The Airport Passenger Terminal. Krieger Publishing Company, January 1992. A general resource textbook that provides information specific to passenger terminals. Provides case studies of eight airport terminals, with associated discussions of ground transportation facilities provided at those terminals. 5. McKelvey, Francis X. and Robert Hornjeff . Planning & Design of Airports, Fourth Edition. McGraw-Hill, 1994

A well respected reference covering all aspects of airport planning and design that briefly addresses circulation roadways. 6. Shapiro, Phillip S., Marcy G. Katzman, Warren E. Hughes, Joseph McGee, Matthew Coogan, M. Allen Hoffman, Emily Van Wagner, and Peter B. Mandle. Intermodal Ground Access to Airports: A Planning Guide. U.S. Department of Transportation, Federal Aviation Administration. December 1996. Paraphrased from the article abstract: Shortly after passage of the Intermodal Surface Transportation Efficiency Act of 1991, the Federal Highway Administration and the Federal Aviation Administration recognized that very little guidance was available for airport operators and metropolitan planning organizations to use in planning intermodal access to U.S. airports. The Intermodal Ground Access to Airports: A Planning Guide was developed to provide guidance to states, metropolitan planning organizations, and airport operators on the types of analyses that should be performed when planning airport access. The airport access planning process and procedures for performing the analyses are described. During development of the Guide, relationships were developed between numbers of originating passengers at U.S. airports and the characteristics of airport access and landside facilities. The types of characteristics that were related to originating passengers included public parking, vehicle trips, terminal curbside design, and mode of access. With respect to curbside and terminal area roadways, the Guide presents examples of the

B-3 sizes, configurations, and layouts of airport curbsides and terminal area roadways and provides metrics for evaluating their capacities and forecasting future needs. 7. Transportation Research Board, National Research Council. Special Report 215: Measuring Airport Landside Capacity. Washington, D.C., 1987. From the Special Report synopsis: “Reviews existing capacity assessment techniques and recommend guidelines that can be used by airport operators, planners, and others who must measure airport landside capacity. Congestion at airport terminal buildings, access roads, and parking areas increasingly threatens the capability of airports to serve additional passengers and air cargo. Measuring the capacity of these airport landside facilities and services is becoming critical. No generally accepted standards exist for gauging the level of service provided by landside facilities and their operations. The report concludes that current knowledge about the performance of various airport landside components is inadequate to support airport landside service standards at this time. Instead, the report recommends a process for measuring airport landside capacity that takes an important first step toward developing such standards.” With respect to curbside and terminal area roadways, Special Report 215 provides a suggested model for estimating curbside requirements obtained from Airport Curbside Planning and Design, by Mandle, Whitlock, and LaMagna (see reference #25 under Analytical Tools). Published Articles and Presentations 8. Leiner, Craig, Massachusetts Port Authority. “Airport Terminal Roadway and Curbside Simulation Models: State of the Practice.” Annual Transportation Research Board Meeting, January 2005. Summarizes the terminal roadway and curbside simulation models and analytical tools commonly used by selected airport operators and consultants. Describes curbside level of service measures and case studies regarding application of available analytical tools and simulation models. 9. Mandle, Peter B., Frank LaMagna, and E.M. Whitlock. Air Passenger Processing—From Home to Gate. Airport Systems Planning and Design, Tenth Annual Short Course at University of California at Berkeley. June 1981. An overview of airport landside operations, including discussion on the function of the airport terminal, air passenger characteristics, planning for passenger processing and passenger terminals, design criteria for selection of passenger ground transportation elements, future airport planning considerations, and case studies.

B-4 10. Shapiro, P.S. and M. Katzman. “Relationships between Airport Activity and Ground Transportation Needs.” Transportation Research Record, No. 1622, Air Transportation, 1998. Summarizes the Intermodal Ground Access to Airports: A Planning Guide (see reference #6 above). Describes relationships between originating passenger activity and airport access and the demand for landside facilities, including access and circulation roadways, curbsides, parking, and commercial vehicle facilities. Presents some of the relationships that were developed, how they were developed, and their importance to airport access planning. Additional relationships that should be developed are suggested. 11. Vumbaco, Brenda J., ed. Airport Landside Operations and Air Service. Transportation Research Record No. 840. Transportation Research Board, National Research Council. Washington, D.C., 1982. Includes various articles on landside operations (e.g., an analysis of the New Orleans airport ground transportation system, guidance for airport curbside planning and design, and air service (e.g., a time-series analysis of intercity air travel volumes and economic justification of air service to small communities). PERFORMANCE MEASURES The following documents describe measures for evaluating the performance and adequacy (i.e., levels of service) of airport curbsides and terminal area roadways. Additional measures are presented in references under Analytical Tools and Simulation Models below. 12. Correia, Anderson and S.C. Wirasinghe. “Evaluating Level of Service at Airport Passenger Terminals: Review of Research Approaches.” Transportation Research Record, No. 1888. Transportation Research Board, National Research Council. Washington, D.C., 2004. From the article abstract: “Establishing measures to evaluate the level of service (LOS) at airport passenger terminals is of interest to airlines and airport operators. Airport LOS has been evaluated at individual airports, but no standard method or reporting system exists…various approaches developed by different agencies and researchers are reviewed. In 1986, FAA commissioned TRB to study ways to measure airport capacity. The resulting study recognized that capacity cannot be evaluated without defining acceptable level of service values, but that little agreement exists on methods to measure LOS for terminal buildings. This paper reviews various approaches developed by others to assist professionals interested in applying one of the methods previously developed but not having access to all published information, especially the new approaches. The

B-5 intent of this review is to motivate new research on the subject, which would facilitate integration of various existing methods or the development of new approaches.” The paper contains an extensive list of references. 13. Mumayiz, S.A. “Evaluating Performance and Service Measures for the Airport Landside.” Transportation Research Record, No. 1296. Transportation Research Board, National Research Council. Washington, D.C., 1991. This paper presents a method for evaluating passengers’ attitudes and their perceptions of and satisfaction with the quality of service at airport terminal facilities. By using this method, levels of service for airport facilities can be determined for different service measures associated with system performance. When used in connection with capacity assessment techniques (e.g., simulation), this method can facilitate evaluation of the operational performance of airport facilities. TERMINAL AREA ROADWA YS The following articles describe the planning, design, operation, and management of terminal area roadways, including analytical tools and simulation models. Several articles describe the causes of terminal area roadway congestion and offer mitigation measures. The effects of weaving—or excessive vehicle movements across traffic lanes, exclusive of typical merging and diverging operations—are also discussed. 14. Duncan, Gavin. “Airport Roadways: Why Congestion Occurs, Mitigation Tools.” Landside Operations Workshop. San Francisco, California, April 11, 2002. Presents overview of airport roadway operations, how they vary from urban and rural roads, the causes and results of congestion, and potential mitigation measures and their applicability. 15. Gosling, Geoffrey D., ed. Ground Access to Airports. Proceedings of two workshops sponsored by the FAA. Institute of Transportation Studies, University of California at Berkeley. December 1994. 16. Iqbal, Muhammad Shahid. “Analytical Models of Weaving Area Operations under Nonfreeway Conditions.” Institute of Transportation Engineers Journal, July 1995, pp. 60-65. Describes the evaluation of nine analytical models to determine nonfreeway weaving.

B-6 17. McGlashan, Jason and James Krzeminski, HDR Engineering. “Weaving Operations at Orlando International Airport—A Comparative Evaluation of Analysis Methods.” Institute of Transportation Engineers, 2001 Annual Meeting. 2001. Speed and volume data were collected from two weaving areas to evaluate the accuracy of analytical weave models used at Orlando International Airport. The paper provides a survey of five analytical weave models (2000 Highway Capacity Manual, 1997 Highway Capacity Manual, 1985 Highway Capacity Manual, New Jersey Institute of Technology model, and Fazio lane shift model) and compares their applicability to Orlando International Airport. The authors concluded that, while many models may be applicable to nonfreeway weave sections, none appear to be universal in their application to different weaving scenarios. 18. Peterson, D.W. “Simulation of Airport Land-side Circulation Using Pathbased Vehicle Routing.” Institute of Transportation Engineers, 2000. From the article abstract: “Planning and management of ground access is both important and required in a competitive environment. Airport access delays have three components: regional access problems (shared use of principal arterials with other travel destinations or transit based operating delay), on-airport access problems (shared use of primary and secondary roads amongst different terminals, frontages, cargo and terminal service operations by different users such as passenger cars, taxis and limos, rental car and hotel vans, and various bus operations), and finally, frontage utilization problems (e.g., space allocation amongst users and modes interference amongst areas and modes, parking inefficiencies, flight schedule based surges in demand, bunching, and level of enforcement). This paper focuses on the second category, on-airport planning, and touches upon the third, frontage utilization. It describes a series of tools developed to facilitate access planning at a major multiterminal international airport in the Northeastern United States planning undergoing significant growth in terminal capacity and changes in mode usage due to construction of an inter-terminal and regional rail access system.” 19. Van Burgsteden, Marco C., Paul E. Joustra, Michiel R. Bouwman, Incontrol Business Engineers, and Mark Hullegie, Amsterdam Airport Schiphol. “Modeling Road Traffic on Airport Premises.” In Proceedings of the 2000 Winter Simulation Conference, ed. J.A. Joines, R.R. Barton, K. Kang, and P.A. Fishwick, pp. 1,154-1,163. From the article abstract: “This paper describes the development of a traffic-modeling tool as an Arena template and two applications of it: one to evaluate alternative designs for the road network on the premises of

B-7 Amsterdam Airport Schiphol and one to assess the effects of traffic signaling on a junction. The tool uses discrete event simulation, very suited for modeling traffic in areas where there are a lot of interactions other than car-following. Generation of the O/D matrix was done automatically by a custom-made application.” ANAL YTICAL TOOLS The following articles present analytical tools or methods for calculating requirements for analyzing the operations of airport curbsides and terminal-area roadways, exclusive of simulation models. The analytical tools presented were most frequently used in (1) estimating roadway and curbside demand requirements; (2) evaluating the relationship between aviation demand and curbside demands; and (3) curbside planning, design, and operations. 20. Cherwony, Walter, Abrams-Cherwony & Associates and Frank A. Zabawski, Booz, Allen & Hamilton. “Airport Terminal Curbfront Planning.” Transportation Research Board, National Research Council. August 1982. Presents suggested method to analyze transportation supply and demand characteristics for airport curbside passenger loading and unloading. The suggested method defines curbfront demand and supply in terms of a time-distance variable of foot-minutes, which is a composite measure of vehicle length and dwell time. Describes the computational procedures for defining transportation demand and capacity. Provides lane utilization factors considering the number of lanes available and nomographs for determining the impact of lane utilization as a function of demand and available length and methods for calculating a volume/capacity ratio. 21. Hillsborough County Aviation Authority, “Terminal Curbfront Demand Modeling.” Tampa International Airport Master Plan Update, Workshop #3, undated. PowerPoint presentation of curbside model input parameters and results developed for Tampa International Airport. Describes existing terminal curbside and roadways, actions of airline passengers at the terminal frontage, and analyses for curbside assignment and roadway activity. 22. JHK & Associates. “Washington Dulles International Airport Main Terminal Expansion: Technical Memorandum, Curbside Activity and Capacity.” 1998. Reviews activity at the Washington Dulles International Airport main terminal curbside, and provides a method for calculating curbside capacity.

B-8 23. KPMG Peat Marwick, Airport Consulting Services. Estimates of Terminal Curbside Frontage Requirements, Newark International Airport, The Port Authority of New York and New Jersey. August 1989. Describes the methodology used to calculate terminal curbside requirements for Newark Liberty International Airport. A spreadsheet model was used. 24. LaMagna, F., Peter B. Mandle, and E.M. Whitlock, Wilbur Smith and Associates. “Guidelines for Evaluation of Airport Landside Vehicular Traffic and Pedestrian Characteristics.” Fifty-Eighth Annual Meeting, Transportation Research Board, January 1979. From the article abstract: “Data are presented describing passenger and vehicular characteristics observed during an extensive study of the landside sectors of Miami International, Denver’s Stapleton, and New York’s LaGuardia Airports, and one terminal in New York’s John F. Kennedy International. Vehicular and pedestrian flow rates at all terminal buildings, curbside, parking, and airport entrances and exits were measured simultaneously and related to the air passenger activity levels, using enplanements and deplanements as indices, which occurred during the same time intervals. Additionally, processing time and service rates were sampled at several locations, including ticket counters, car rental areas, passenger security check points, parking cashier operations, and other locations within the terminal. This paper presents a compendium of these processing times observed at these three airports. Representative pedestrian and vehicular flow rates per passenger and processing times are presented for use as planning tools.” 25. Mandle, Peter, E.M. Whitlock, and F. LaMagna. “Airport Curbside Planning and Design.” Transportation Research Record No. 840, Transportation Research Board, National Research Council. Washington, D.C., 1982. From the article abstract: “A method of estimating airport curbside demand and procedures for adjusting this demand for various service levels and operating conditions are discussed. Data are presented describing the effects of passenger and vehicular activity at the airport curb areas. Operational problems that typically occur at an airport curb are discussed. Factors influencing operational problems at the curb are addressed, as well as a means of determining curb frontage requirements, demands, and relating these to levels of service, based on observations at six major U.S. airports. This approach affords airport planners an opportunity to measure the degree of use of the curbside area and to correlate curbside requirements to the effective length of curb. Volumes of originating and terminating passengers were found to be of prime importance in forecasting demand as contrasted to total enplanements and

B-9 deplanements. The enforcement level of parking regulations and corresponding vehicle dwell time was found to strongly influence curbside capacity. Design considerations such as roadway and sidewalk widths that affect the efficiency of the curb are presented, and criteria are recommended.” 26. Parizi, M.S. and J.P. Braaksma. “Dynamic Capacity of Airport Enplaning Curbside Areas.” Transportation Research Record, No. 1373, Airport Landside Planning and Operations, 1992. From the article abstract: “An analytical model based on the theory of time-space was developed to calculate the dynamic vehicular capacity of the enplaning curbside area at airport passenger terminal buildings. The enplaning curbside area was considered as a system, and most of the variables that affect the capacity of this system were taken into account. To calculate the practical capacity, two distribution functions were developed. First, the traffic distribution around the doors of the terminal building was analyzed, on the basis of drivers' parking space preference, in the form of a binomial function. Second, weighting functions were developed and calibrated on the basis of users' door preference for unloading, in the case of more than one door, in the form of a modified binomial distribution. Using these functions, the percentage of distribution of traffic as well as the practical dynamic capacity of the enplaning curbs were found.” 27. Piper, Heinz Peter, Prof. Dipl.-Ing. “Calculation method for the number of short-term carpark spaces at airport terminals.” Airport Forum, 1993, pp. 52-53. The article discusses passenger walking distance as a performance measure, and provides a method for determining the number of shortterm spaces—i.e., spaces along the curbside—required in front of an airport terminal. The Airport Forum editors also provide a description of the Advanced Landside Performance System (ALPS) model. 28. Tilles, Richard, et al. “Curb Space at Airport Terminals,” Traffic Quarterly, pp. 563-582, October 1973. The article presents methods of curb length computation at airports, an analysis of factors that determine such lengths, and commentary on considerations of curb design and cost. Regarding curb length computation, the author discusses rules of thumb and simulation, and asserts that a statistical process using queuing theory is better suited to most airport design requirements. A statistical analysis methodology is discussed. Factors affecting curb length requirements are presented, as follows: (a) vehicle arrival rate and (b) total time a vehicle remains at a

B-10 curb (mean service time). Finally, design and cost considerations are described, including the use of one or two levels, width of the roadway, length of the curb, and imposing charges on users of the curb area. 29. URS Greiner, “Curbside Needs Evaluation for Port Columbus International Airport.” undated. URS Greiner conducted a demand/capacity needs evaluation of the curbside conditions at the terminal. This memorandum summarizes the inventory surveys, specific analyses, and the results. 30. Whitlock, E.M. and E.F. Cleary, Wilbur Smith and Associates. “Planning Ground Transportation Facilities for Airports.” Presented at the 48th Annual Meeting of Committee on Passenger Transportation Economics, undated. Paraphrased from the article abstract: This article summarizes expected changes in air travel characteristics. Broad considerations also are suggested for improving airport utility and ground transportation systems. The authors evaluated transportation facilities at San Francisco International, Boston Logan International, and Detroit Metropolitan Wayne County airports. Correlations were established for modal split, traffic variation, passenger and vehicle relationships, curb use, and parking characteristics and needs. The following changes in airline travel are expected to influence ground transportation requirements: (a) introduction of larger aircraft; (b) reduction in per capita travel costs; (c) shift from predominantly business travel by air to more recreational travel; (d) large increases in goods movements by air; (e) cheaper per-ton costs of good movements; and (f) more pronounced peak-hour traffic. SIMULATION MODELS The following documents discuss simulation of airport curbsides and roadway operations, including (1) the presentation of new simulation models; (2) the evaluation of the effectiveness of existing models; and (3) the discussion of case studies conducted using curbside simulation models at various airports. The following documents are organized by model, as follows: • • • • • •

Advanced Landside Performance System Leigh Fisher Associates Curbside Traffic Simulation (LFACTS) Mobility Analysis and Simulation Tools (MAST) Terminal, Roadway, and Curbside Simulation (TRACS) VISSIM Other simulation models


Advanced Landside Performance System™ (ALPS2000) The JKH Mobility Services division of Kimley-Horn and Associates, Inc., developed the ALPS model to simulate complex multimodel transportation environments, including airport landside systems. The following documents relate to the model’s underlying assumptions, features, and uses: 31. Lott, J. Sam, Kimley-Horn and Associates, Inc. “Hybrid Simulation Techniques for the Analysis of Landside and Terminal Capacity Issues.” PowerPoint Presentation. FAA/NASA/Industry Airport Planning Workshop. September 12, 2006. Describes the holistic methodology of the ALPS2000 model, and presents methods for hybrid simulation modeling—i.e., focusing higher processing power on locations where significant analytical benefits would result. The objective is faster, more-efficient simulation of airport ground transportation systems. Case studies from previous simulation efforts are presented. “ALPS2000™ is a set of computer simulation tools used to evaluate the airport landside operations, especially on the roadways and terminal curbsides. ALPS2000 allows the modeler to create micro simulations that encompass the pedestrian and vehicular movements within the terminal roadway system. “Fundamental to the ALPS concept is the ability to generate passenger demands based on airline flight schedules. Passenger characteristics, such as visitor characteristics and trip timing, are applied to the flight schedules to generate the passenger demands throughout a 24-hour period. Then vehicular characteristics, such as mode split and vehicle occupancy, are applied to the passenger demands to generate the vehicular activity. “Once the vehicular activity is generated, the individual vehicles are routed through the roadway network and stop at their respective curbsides. The ALPS program allows visualization of roadway and curbside operations, including congestion levels, and captures many quantitative results such as travel times. The model is able to simulate all airport roads, parking facilities, curbsides, toll plazas, pedestrian ways and transit systems (such as LRT and APM systems). “One of the major features of ALPS2000 is that it is a highly visual tool. All of the results can be displayed to show the detailed movement of people and vehicles. This feature allows for all stakeholders in the airport environment to better understand the results of the analysis. Additional features of the model are its ability to (1) evaluate passenger flow aspects for an entire day (24 hours), (2) differentiate among types of vehicles on the roadway, (3) coordinate with other transportation models, (4) depict

B-12 visualizations of bottlenecks and trapped vehicles, (5) identify forced vehicle recirculation at the curbsides, and (6) [identify] conflicts due to pedestrians crossing curbside roadways." Leigh Fisher Associates Curbside Traffic Simulation (LFACTS) The LFACTS model was developed by Leigh Fisher Associates (now Jacobs Consultancy) to simulate traffic operations at airport curbsides. The following documents prepared by Leigh Fisher Associates' staff relate to the model's underlying assumptions, features, and uses. 32. Duncan, W. Gavin R. and Hugh Johnson. “Development and Application of a Dynamic Simulation Model for Airport Curbsides.” The 2020 Vision of Air Transportation. Engineering Issues and Innovative Solutions. Proceedings of the 26th International Air Transportation Conference, 2000., American Society of Civil Engineers From the article abstract: “The paper describes a proprietary model, Leigh Fisher Associates' Curbside Traffic Simulation (LFACTS), developed to simulate vehicular traffic operations on airport curbsides. The model results can be used to evaluate alternatives and to help airport operators deal with existing and anticipated airport ground traffic congestion problems. The basic theory and assumptions behind LFACTS are provided in the paper. Also provided are examples of how LFACTS has been used to answer specific questions at four United States airports.” 33. Hoffman, M. Allen. “Planning and Design of Airport Curbsides.” Conference on the Optimal Design and Management of Airport Curbs, Airport Ground Transportation Association and BusCon 2001, September 10, 2001. PowerPoint presentation that describes curbside requirements and analysis, selection of appropriate analysis methodology, and potential curbside solutions. In relation to curbside analysis, manual/spreadsheet procedures and their limitations are listed. The presentation describes LFACTS simulation modeling, and lists typical simulation applications. Mobility Analysis and Simulation Tools (MAST) 34. MAST, developed by DMJM Aviation/AECOM has been used in several airport ground access studies to help evaluate future ground transportation improvements. MAST is an integrated set of computer programs that can be used to model the traffic conditions on roadways and curbs at medium to large airports, including the time of day variations and complex traffic variations associated with multiple-terminal airports.


Terminal, Roadway, and Curbside Simulation (TRACS) The TRACS model is a discrete-event simulation model developed by Trans Solutions to model airport curbsides and terminal area roadways. The following documents describe the model's underlying assumptions, features, and uses. 35. Bender, Gloria G. and Kuo-Yang Chang. SABRE Decision Technologies. “Roadway and Curbside Traffic Simulation for Las Vegas McCarran International Airport.” Presented at the American Society of Civil Engineers International Conference on Airport Modeling and Simulation, May 1997. From the article abstract: “Simulation modeling is a useful tool to study the capacity and operation of the airport ground transportation access system (GTAS). This paper compares simulation analysis to other analytical methods and then provides a case study to illustrate how simulation modeling was used as an effective GTAS planning tool at Las Vegas McCarran International Airport. Since most state-of-the-art traffic simulation models either do not have curbside parking and pedestrian crossing logic or the logic does not provide appropriate resolution to answer the questions necessary to support detailed planning, SABRE developed a stochastic, discrete-event simulation model to replicate the behavior of vehicles on the airport curbside roadway. The paper describes the simulation model of the curbside roadways at the LAS main terminal and, among other things, describes the impacts of curbside control measures.” 36. Chang, Kuo-Yang. “A Simulation Model for Analyzing Airport Terminal Roadway and Traffic and Curbside Parking.” Dissertation submitted to the Faculty of the Graduate School of the University of Maryland, College Park in partial fulfillment of the requirements for a Doctor of Philosophy degree, 2001. From the article abstract: This article “…proposes a computer simulation model that helps airport planners and managers conduct operational analyses of airport terminal roadway traffic and curbside vehicle parking activities. The major logic components built into the model include those for vehicular traffic generation, vehicle movement, lane selection and changing, curbside parking space selection, and pedestrian crosswalks. The major output statistics generated by the model, which also demonstrate the model’s performance capability, include vehicle system time, number of vehicles entering and leaving the terminal roadway, number of vehicles parked along the curbside, number of vehicles queued at the terminal roadway entry, number of vehicles that cannot find a curbside parking space due to congestion, and vehicle delays.” 37. Chang, Kuo-Yang, A. Haghani, and G.G. Bender. “Traffic Simulation at Airport Terminal Roadway and Curbside.” The 2020 Vision of Air Transportation. Engineering Issues and Innovative Solutions. Proceedings of the

B-14 26th International Air Transportation Conference, 2000., American Society of Civil Engineers From the article abstract: “The paper presents a working simulation model that can be used as a tool to assist airport planners, decision makers, and operators to evaluate the performance of airport curbside parking facilities. The model validation results show accurate traffic flow predictions for both arrival and departure areas. Also, the results show that the model can predict both exit flow and vehicles' time spent in the curbside facilities. This model can easily be embedded in a decision support system for airport planners and decision makers to examine different scenarios during planning and design stages.” 38. Hargrove, B. and E. Miller. “TRACS—Terminal, Roadway, and Curbside Simulation—A Total Airport Landside Operations Analysis Tool.” AirportAirspace Simulations: A New Outlook, Transportation Research E-Circular, Transportation Research Board, National Research Council. 2002. “TRACS—Terminal, Roadway, and Curbside Simulation—is a flexible planning tool that can be linked to other simulation products to provide a comprehensive assessment of terminal performance and its interaction with the airspace, airfield, and roadways systems.” 39. Siow, B.T., O. Kivanc, G. Bender, R. Evlioglu, and C. Tunasar. “Managing Airport Traffic Disruptions during Construction.” Designing, Constructing, Maintaining, and Financing Today’s Airport Projects, Proceedings of the Twenty-Seventh International Air Transportation Conference, American Society of Civil Engineers, 2002. From the article abstract: “The George Bush Intercontinental Airport/Houston (IAH) has multiple construction projects planned for the next several years. All of these projects will involve a temporary closure of roadways or traffic lanes, as well as changing traffic operations in and around the airport. Two separate, but correlated simulation models are used to represent the vehicular traffic operations at IAH. The Terminal and Curbside Roadways are modeled using a discrete event simulation model, the TRACS (TransSolutions' proprietary terminal, roadway, and curbside simulation tool), which allowed a detailed representation of vehicle parking to accommodate passenger loading and unloading, pedestrian crossing, and vehicle re-circulation. TRACS' trip generator and model logic is validated through extensive field data. Airport Access Roadways and Regional Freeways covering 25 square miles are modeled by CORSIM, a microscopic traffic simulation model developed by the Federal Highway Administration. This paper presents the methodology in identifying the critical construction phases to be studied, the modeling framework, and how it is used to assess and manage construction impact.”

B-15 40. Tunasar, Cenk, Gloria Bender, The SABRE Group, and Holland Young, City of Austin. “Modeling Curbside Vehicular Traffic at Airports.” Proceedings of the 1998 Winter Simulation Conference, ed. D.J. Medeiros, E.F. Watson, J.S. Carson, and M.S. Manivannan, pp. 1,113-1,117. The article describes the use of discrete event simulation in modeling curbside vehicular traffic at airports. Simulation results are described in terms of level of service. VISSIM VISSIM was developed by the German company Planung Transport Verkehr AG (PTV) to simulate various ground transportation scenarios, and is known throughout the industry for its 3-D visualization features. The model has been applied to airport landside systems. The following documents provide a comparison of VISSIM and other roadway simulation models and describe airport applications of VISSIM plus its underlying assumptions, features, and uses. 41. Choa, Fred, Ronald T. Milam, and David Stanek. “CORSIM, PARAMICS, and VISSIM: What the Manuals Never Told You.” Proceedings of the Ninth Transportation Research Board Conference on the Application of Transportation Planning Methods. Baton Rouge, Louisiana. April 6-10, 2003. From the article abstract: “With the increasing use of microsimulation traffic software in operations analysis, the need to identify which tool to use and the ability of the software to provide traditional traffic engineering measures of effectiveness consistent with the 2000 Highway Capacity Manual (2000HCM) has become a major area of debate. This paper provides a comparison of the three major traffic simulation software programs in use today and the results of the evaluation matrix developed by the authors for a freeway and interchange improvement project involving unique geometrics, ramp controls, and weaving constraints. The three simulation programs considered in the paper are listed as follows: (1) CORSIM, developed by the Federal Highway Administration (FHWA), is one of the most commonly used micro-simulation programs for modeling vehicle traffic operations. (2) PARAMICS, developed by Quadstone Limited, a Scottish company, is a software program used to model the movement and behavior of individual vehicles and transit on local arterial and regional freeway networks. (3) VISSIM, developed by Planung Transport Verkehr (PTV), a German company, is one of the most sophisticated microsimulation software programs available and provides significant enhancements in terms of driver behavior, multi-modal transit operations, interface with planning/forecasting models, and 3-D simulation. This paper describes several key factors that may affect the decision on which software to use for a specific project involving a freeway interchange and the consistency of the model output to traditional traffic engineering measures of effectiveness.”

B-16 42. Siecke, Ronald C., P.E., HNTB. “Exploring New Frontiers in the Use of VISSIM for Airport Simulation.” PowerPoint Presentation. FAA/NASA/Industry Airport Planning Workshop. September 12, 2006. PowerPoint presentation that reviews appropriate instances for using simulation modeling, the VISSIM model, VISSIM as a component of an airport’s “simulation toolbox,” and challenges and opportunities in applying VISSIM to airport ground transportation issues. 43. Trueblood, Michael T. “Airport Curbside Modeling Using VISSIM.” 2006 Annual Meeting and Exhibit Compendium of Technical Papers, Institute of Transportation Engineers. 2006. From the article abstract: “Recently, VISSIM has added a new feature that greatly enhances curb modeling at airports. The purpose of this paper is to promote this feature of VISSIM as a viable tool for analyzing curbside operations of airport terminals. Airport terminals can be extremely congested because of the mixture of various transportation modes (i.e., pedestrians, limos, rental car buses, and passenger vehicles). The use of VISSIM can be a great tool for showing the benefits of relocating various activities offsite to improve operations along the curb. The following VISSIM items and their importance in effectively simulating curbside modeling will be covered in the paper: (1) link and connectors; (2) pedestrian interaction; (3) dwell time by vehicle classification; and (4) selection of lane choice and curb location.” Other Simulation Models The following documents describe the development, underlying assumptions, features, and uses of other models developed for or applied to airport landside systems. 44. Hall, Charles A. and Charles E. Dare. “A Simulation Model for an EnplaningPassenger-Vehicle Curbside at High-Volume Airports.” Undated (c. 1976/77). This paper describes how a simulation was used to determine the efficiency of the airport’s enplaning curbside. Denver Stapleton International Airport was modeled, and the model can easily be modified for other airports. The computer simulation methodology is discussed. The model predicts effectiveness of the measures suggested to improve levels of service. 45. McCabe, L. and T. Carberry. “Simulation Methods for Airport Facilities.” Transportation Research Board Special Report No. 159, Transportation Research Board, National Research Council. Washington, D.C., 1975. From the article abstract, “The most realistic method of quantitatively approaching airport landside traffic problems appears to be computer simulation of airport landside traffic flows. This paper describes how the

B-17 simulation of the landside portion of an airport complex can be used to represent or model the airport landside system to accurately determine the flow and holding capacity and the associated delays of the airport landside. A review of existing computer simulation models indicates that the Bechtel and TAMS models are most suitable for this purpose. They can produce the required distributions of delay, queue lengths, and occupancies for the boundaries specified. The major adaptation that would appear necessary to complete the landside analysis capability would be including a model of the curbside as a server of finite capacity rater than representing the time spent at curbside as a dwell time.” 46. Mumayiz, S.A. and P. Schonfeld, eds. Airport Modeling and Simulation: Conference Proceedings. Arlington, Virginia, August 17-20, 1997. From the article abstract: “The subjects covered by these papers range from air traffic management to terminal design. Specifically, topics such as curbside traffic simulation, air traffic flow, financial modeling, modeling applications, travel forecasting, and landside simulation are covered. Aviation planners, engineers, and managers will find these proceedings of interest.” 47. Verbraeck, Alexander and Edwin Valentin. “Simulation Building Blocks for Airport Terminal Modeling.” Proceedings of the 2002 Winter Simulation Conference. Editors: Yucesan, Chen, Snowdon and Charnes. 2002. From the article abstract: “Airports are an ideal application area for simulation. The processes are in a continuous state of change, are complex and stochastic, involve many moving objects, and require a good performance that can be measured using several different performance indicators. Within airports, but also between airports, the same kind of questions are answered over and over again. Often, however, new simulation models are built for each question, if possible copying some parts of previous models. Structured reuse of simulation components is rarely seen. This paper shows an approach for airport terminal modeling that departs from the assumption that reusable simulation building blocks can form the core of a powerful airport modeling tool, which is able to answer different questions at airports better and faster than traditional models. The building blocks have been implemented in the commercially available simulation language eM-Plant. Several studies carried out with this library were very successful.” CURBSIDE OPERATIONS The following documents are related to curbside operations, and discuss (1) calculation of curbside requirements, (2) optimization of curbside allocation, (3) management of the curbside, and/or (4) other measures adopted to improve level-of-service at the airport curbside. Because these documents provided

B-18 background information, and not specific information on analytical tools or simulation models for airport curbsides and roadways, no annotations are provided. 48. Bianconi, Peter, Airport Professional Services Branch, Transport Canada. “Draft – Chapter V—Operational Needs of Transport Modes.” August 15, 1984. 49. Brown, Deborah Ross, Ground Transportation Coordinator at Stapleton International Airport. “Cleaning up the Curb, Airport Planning.” 58th Annual Conference and Exposition, May 21, 1986. 50. Clippinger, Susan E., Massachusetts Port Authority, and Alex Taft, Cambridge Systematics, Inc. “Managing a Scarce Resource—Massport’s Recent Experience with Curbside Control.” Transportation Research Board, National Research Council. January 23, 1989. 51. Hall, Richard W. and Marjorie Brink, Peat, Marwick, Mitchell and Co. “Control of Curbside Use,” Institutional and Municipal Parking Congress Seminar, Clearwater Beach, Florida, October 28, 1983. 52. Hunnicutt, James M. “Nine Ways to Curb Landside Congestion.” Airport Services Management, September 1986. 53. Hoffman, M. Allen, Leigh Fisher Associates. “Airport Curbside Traffic Operations and Management.” International Parking Institute, Airport Parking and Ground Transportation Operations, Las Vegas, Nevada, December 4, 1997. 54. KPMG Peat Marwick Airport Consulting Services. Analysis of Commercial Curbside Utilization and Private Vehicle Circulation Patterns. July 17, 1989. 55. KPMG Peat Marwick, Airport Consulting Services. Terminal Building Curbside Management Study, Boston Logan International Airport, Massachusetts Port Authority. June 1991. 56. Mandle, Peter B., Jacobs Consultancy. “Curbside Planning and Operations,” Airport Ground Transportation Planning and Operations Seminar, San Francisco, April 5-6, 2006. 57. Mandle, Peter B., Wilbur Smith and Associates. “Airport Curb Operations and Practices at Major United States Airports.” 1986. Presentation before Transportation Research Board 58. Mandle, Peter B. and Jessica Wyatt, Leigh Fisher Associates. “Airport Curbsides,” Landside Operations Workshop, April 12, 2002. 59. Meehan, James A. “Preventing Curbside Chaos.” Airport Forum, Volume 20, No. 2. February 1990.

B-19 60. Rahman, A.K.A., H.O. Al-Bar, and N.A. Al-Zaitooni. “Evaluation of Curbsides’ Capacity and Service Level at King Abdul Aziz International Airport (KAIA) Terminals in Jeddah, Saudi Arabia.” Institute of Transportation Engineers, 1999. 61. Roberts, Bruce, Vice President and General Manager, Airport Service, Inc. “Common Curbside Problems at U.S. Airports.” Airport Service, Inc., undated. 62.

“St. Louis Smoothes Traffic Flow, Boosts Safety with Curbside Redesign," Airports, September 3, 1991.

63. Street, Jim. “Curbing Curbside Gridlock,” Airport Magazine, March/April 1991. 64. Wilbur Smith and Associates. “Suggested Curb Utilization Improvement Plan for Dallas/Fort Worth International Airport.” February 28, 1986. 65. Yee, Stephen, Airport Manager, Los Angeles International Airport. “Ground Transportation Program at Los Angeles International Airport.” AAAE/Transport Canada Airport Management Conference, July 30, 1991. 66. Zatopek, Joan C., Leigh Fisher Associates. “Managing Commercial Ground Transportation Vehicles.” Airport Ground Transportation Planning and Operations Seminar, San Francisco, April 5-6, 2006. 67. Institute of Traffic Engineers, Trip Generation, 7th Edition. Washington, D.C., 2003. 68. HCM. Highway Capacity Manual, TRB, 2000. Transportation Research Board, National Research Council. Highway Capacity Manual. Washington, D.C., 1987. 70. MUTCD. Manual of Traffic Control Devices, FHWA. Federal Highway Administration, Manual on Uniform Traffic Control Devices. Revision 2. Washington, D.C., 2007. 71. Institute of Traffic Engineers, Traffic Engineers Handbook, Washington, D.C., 2009.


ACRP Report 40 Airport Curbside and Terminal Area Roadway Operations Appendix C SUMMARY OF TERMINAL AREA ROADWA Y TRAFFIC VOLUME SURVEYS As part of Airport Cooperative Research Program (ACRP) Project 7-02, the research team conducted traffic surveys at Washington Dulles International Airport and Oakland International Airport for a period of 7 consecutive days in each location using automatic traffic recorders (ATRs), staff observations, and cameras. This appendix presents a summary of the data collected. WASHINGTON DULLES INTERNATIONAL AIRPORT Field Survey Schedule Sunday, July 22, 2007, through Saturday, July 28, 2007. ATR Locations (see Figure C-1) A This location is not shown on Figure C-1. It is adjacent to Daily Garage 2, along the north section of the terminal loop road opposite the Main Terminal building, which is the weaving segment that the research team wanted to monitor. (See camera location 5 described below.) B This location—where the total volume of traffic entering the curbside roadways was recorded—is prior to the point where the curbside roadway split to three separate roadways one pick-up, drop-off, and commercial vehicles, respectively and after the entry to the hourly parking area. . C Upper level (departures level curbside). D Middle level passenger pick-up curbside used by taxicabs and door-to-door vans. E Lower level passenger pick-up curbsides used by private vehicles, limousines, and courtesy vehicles. F Return-to-terminal traffic volumes. G Exiting traffic volumes.


Staff Observation Locations Staff were positioned at the locations shown on Figure C-1 to gather the following data: 1 and 4

Upper level (Level 3) dwell time measurements

2 and 5

Middle level dwell time measurements

3 and 6

Lower level dwell time measurements


Vehicle classification survey of all vehicles approaching the curbside at the roadway entry

Camera Locations Cameras were positioned to record traffic volumes at the following locations, which correspond with the locations of staff positions on Figure C-1: 1 West end of upper level curbsides 2 West end of lower level curbsides 3 East end of middle and lower level curbsides 4 East end of lower level curbsides 5 Weaving area on north side of terminal loop road 6 View of westside of curbside roadways to measure the speed of vehicles 7 View of eastside of curbs to measure the speed of vehicles Summary of Data Figures C-2 and C-3 present the variations in daily and hourly traffic volumes entering and exiting the terminal area. As shown, Sunday was the busiest day of the week, while the busiest hour occurred between 3:00 p.m. and 4:00 p.m. The Sunday peak hour was about 10% busier than the other daily peak hours. Figures C-4 and C-5 present the variations in daily and hourly private vehicle traffic volumes on the lower-level arrivals and upper-level departures curbside roadways. Again, the highest traffic volumes occurred on Sunday, but a pronounced peak occurred on Friday on the departures curbside. While hourly distributions of traffic on the entering and exiting roadways and arrivals level curbside were consistent from day to day, the departures curbside exhibited a less consistent pattern after 4:00 p.m.

C-3 These variations reflect the East Coast and international peaks associated with airline traffic at Washington Dulles International Airport. Appendix D summarizes the dwell time surveys.


Figure C.1


Figure C-2 Daily Traffic Volumes Washington-Dulles International Airport July 22, 2007 to July 28, 2007 Airport Entrance Roadway 3,500


Vehicles per Day













Day of the Week

Hourly Traffic Volumes Washington-Dulles International Airport July 22, 2007 to July 28, 2007 Airport Entrance Roadway 3500


Vehicles per Hour


Sunday Monday


T uesday Wednesday


Thursday Friday Saturday



0 0:00






12:00 Time of Day








Figure C-3 Daily Traffic Volumes Washington-Dulles International Airport July 22, 2007 to July 28, 2007 Airport Exit Roadway *Does not include exits from parking lots 1,800



Vehicles per Day














Day of the Week

Hourly Traffic Volumes Washington-Dulles International Airport July 22, 2007 to July 28, 2007 Airport Exit Roadway *Does not include exits from parking lots 1600


Vehicles per Hour


Sunday Monday Tuesday


Wednesday Thursday Friday Saturday





0 0:00






12:00 Time of Day








Figure C-4 Daily Traffic Volumes Washington-Dulles International Airport July 22, 2007 to July 28, 2007 Lower Level Arrivals Curbside Roadway 2,000 1,800 1,600

Vehicles per Day

1,400 1,200 1,000 800 600 400 200 Sunday







Day of the Week

Hourly Traffic Volumes Washington-Dulles International Airport July 22, 2007 to July 28, 2007 Lower Level Arrivals Curbside Roadway 1800


1400 Sunday Monday Tuesday

Vehicles per Hour


Wednesday Thursday Friday







0 0:00






12:00 Time of Day








Figure C-5 Daily Traffic Volumes Washington-Dulles International Airport July 22, 2007 to July 28, 2007 Upper Level Departures Curbside Roadway 1,400


Vehicles per Day













Day of the Week

Hourly Traffic Volumes Washington-Dulles International Airport July 22, 2007 to July 28, 2007 Upper Level Departures Curbside Roadway 1400


Vehicles per Hour


Sunday Monday T uesday Wednesday Thursday


Friday Saturday




0 0:00






12:00 Time of Day








OAKLAND INTERNATIONAL AIRPORT Field Survey Schedule Thursday, August 2, 2007, through Wednesday, August 8, 2007 ATR Locations (see Figure C- 6) A Inner curbside lanes in front of Terminal 1 used by private vehicles for dropping off and picking up passengers B Middle curbside lanes used by some commercial vehicles D Inner curbside lanes in front of Terminal 2 used by private vehicles for dropping off and picking up passengers E Outer curbside lanes used by some commercial vehicles F Terminal recirculation roadway G Terminal exit roadway H Terminal exit roadway, including traffic from Neil Armstrong Way Staff Observation Locations Staff were positioned at or near the locations shown on Figure C-6 to gather the following data: 1 Inner curbside dwell time measurements 2 Middle curbside dwell time measurements 3 Outer commercial vehicle lane dwell time measurements 4 and 5 Vehicle classification survey of all vehicles approaching the curbside Camera Locations Cameras were positioned to record traffic volumes at the following locations shown on Figure C-6: •

Curbside entrance roadways

In front of Terminal 1, to record curbside and crosswalk interactions

In front of Terminal 2, to record curbside and crosswalk interactions

On the inner curbside at Terminal 2 to record private vehicle operations



Summary of Data Figure C-7 presents the variations in daily and hourly traffic volumes on the roadways exiting the terminal area. As shown, Sunday was the busiest day of the week, but the busiest individual peak hour occurred on Friday evening. Whereas the counts at Washington Dulles International Airport exhibited three to four distinct peaks throughout the day, the counts at Oakland International Airport exhibited a slight peak in the morning followed by a sustained busy period through the remainder of the day. Figure C-8 presents the variations in daily and hourly traffic volumes on the curbside roadway (which serves both departing and arriving airline passenger vehicular traffic). During the three surveyed days, the highest total volume as well as the highest peak hour volume occurred on Saturday. Similar to the pattern observed for traffic exiting the airport, the curbside traffic exhibited a slight peak in the morning followed by a period of sustained activity through the remainder of the day. However, the curbside traffic also exhibited a second peak in the late morning, followed by a third peak in the late evening.


Figure C-7 Daily Traffic Volumes Oakland International Airport August 2, 2007 to August 8, 2007 Airport Exit Roadway 25,000

Vehicles per Day












Day of the Week

Hourly Traffic Volumes Oakland International Airport August 2, 2007 to August 8, 2007 Airport Exit Roadway 1600




Vehicles per Hour

Monday Tuesday Wednesday Thursday Friday







0 0:00






12:00 Time of Day








Figure C-8 Daily Traffic Volumes Oakland International Airport August 2, 2007 to August 8, 2007 Airport Curbside Roadways 45,000






10,000 Counts for Sunday - Wednesday not available 5,000








Day of the Week

Hourly Traffic Volumes Oakland International Airport August 2, 2007 to August 8, 2007 Airport Curbside Roadways 3500


2500 Vehicles per Hour

Vehicles per Day


Thursday Friday Saturday



1000 Counts for Sunday - Wednesday not available 500

0 0:00






12:00 Time of Day








ACRP Report 40 Airport Curbside and Terminal Area Roadway Operations Appendix D SUMMARY OF CURBSIDE ROADWA Y CHARACTERISTIC SURVEYS As part of Airport Cooperative Research Program (ACRP) Project 7-02, the research team conducted roadway traffic volume, dwell time, and vehicle classification surveys at Washington Dulles and Oakland international airports. This appendix summarizes the surveys of curbside dwell times and vehicle classifications (traffic volume data are presented in Appendix C). Additionally, the survey data used to determine the propensity to double park at two other airports (Seattle-Tacoma and Portland international airports) are summarized herein. Also, validation of the weaving module contained in the Quick Analysis Tool for Airport Roadways (QATAR) model using video captured at San Francisco International Airport is presented at the end of this appendix. DWELL TIMES Dwell time surveys were conducted at Washington Dulles and Oakland international airports. A summary of the data collected at these airports, as well as additional data collected by the research team through other efforts at Memphis, Austin-Bergstrom, and Portland international airports, are presented in Table D-1. T able D-1 Summary of Dwell Time Surveys (in minutes) Enp laning Curbsid e

W ashing ton Dulles International A irp ort Up per Lev el 2007 Year 464 N um ber of Observ ations Priv ate v ehicle 2.40 T axicab 1.88 Lim ousine 0.62 Door -to-door v an 3.71 O ff Airport parking v an A irp ort parking bus 4.18 Em ployee p arking bus 1.38 H otel cou rtesy v an 1.15 Rental car bu s Charter / tou r bus Public transit Sou rce: Jacobs Consu ltancy , Decem ber 2008

Mem p his International Airport Dep artu res Lev el 2007 193 1.68 1.87

0.58 0.72 0.63 1.12 0.52

Mixed Curbside

Dep laning Curbsid e

AustinBerg strom International Airport Dep artures Lev el 2006 107

Portland International Airport Departures Lev el 2006 65

W ashing ton Dulles International A irp ort Midd le Lev el 2007 559

2.03 1.73 1.58 3.10 1.48 1.27

1.57 1.98



2.13 0.58


W ashing ton Dulles International Airp ort Low er Lev el 2007 529


5.52 2.72 0.50


Oakland International Mem phis Airport Mixed International Dep artures Airport and Arriv als Arriv als Lev el Lev el 2006 2007 177 568

2.35 2.60 2.18 3.62 3.49

1.21 0.97 4.50 2.41 2.07 0.15 1.67 2.00 0.67 0.42


PROPENSITY TO DOUBLE PARK To determine the propensity of drivers to double and triple park in curbside loading and unloading areas, snapshots of the number of vehicles stopped in each lane of a curbside were recorded for several time intervals throughout a peak period. The data presented below were previously collected by members of the research team at Seattle-Tacoma and Portland international airports. The average percent of vehicles double parked at Seattle-Tacoma International Airport did not change significantly based on time of day; however, at both airports, the number of vehicles double and triple parked changed frequently within short time intervals. Furthermore, the percent of vehicles double parked at Portland International Airport accounted for only 20% of vehicles stopped at the arrivals level curbside compared to 54% at Seattle-Tacoma International, indicating that this characteristic varies significantly between the airports.



VEHICLE CLASSIFICATION SURVEYS Vehicle classification surveys are conducted to identify 100% of the vehicular traffic on a roadway according to one of several classifications (i.e., private vehicle, taxicab, hotel shuttle bus, etc). These data were collected at the same locations as the dwell time and traffic volume surveys presented above.

Summary of Vehicle Classification Surveys Oakland International Airport Thursday

Private vehicles T axicabs Limousines Door-to-door shuttle (SuperShuttle) Off-Airport parking courtesy shuttle Airport parking bus (Red Lot, Employee) Hotel/motel courtesy shuttle Rental car bus Public buses Charter/tour bus Other (Airport vehicles, police, etc.)

12:00pm to 3:00pm V olume Percent 2740 74.2% 238 6.4% 99 2.7% 96 2.6% 120 3.2% 119 3.2% 47 1.3% 47 1.3% 39 1.1% 7 0.2% 143 3.9%

Private vehicles T axicabs Limousines Door-to-door shuttle (SuperShuttle) Off-Airport parking courtesy shuttle Airport parking bus (Red Lot, Employee) Hotel/motel courtesy shuttle Rental car bus Public buses Charter/tour bus Other (Airport vehicles, police, etc.)

Washington Dulles International Airport Sunday Monday Arrivals Level Departures Level 1:30pm to 4:30pm 7:00am to 10:00am V olume Percent V olume Percent 2319 70.2% 1971 84.8% 396 12.0% 242 10.4% 121 3.7% 8 0.3% 29 0.9% 19 0.8% 82 2.5% 16 0.7% 125 3.8% 0 0.0% 42 1.3% 32 1.4% 32 1.0% 1 0.0% 116 3.5% 9 0.4% 21 0.6% 2 0.1% 19 0.6% 23 1.0%

Source: Jacobs Consultany , December 2008 Traffic Surveys conducted by WIL TEC Inc., July/August 2007

5:00pm to 8:00pm V olume Percent 2996 78.2% 259 6.8% 112 2.9% 79 2.1% 123 3.2% 128 3.3% 40 1.0% 36 0.9% 36 0.9% 5 0.1% 18 0.5%

Friday 6:00am to 9:00am Volume Percent 1828 68.6% 210 7.9% 98 3.7% 74 2.8% 1 11 4.2% 120 4.5% 60 2.3% 42 1.6% 39 1.5% 5 0.2% 76 2.9%

4:00pm to 7:00pm Volume Percent 3151 79.9% 220 5.6% 89 2.3% 89 2.3% 1 17 3.0% 1 16 2.9% 42 1.1% 34 0.9% 40 1.0% 7 0.2% 37 0.9%


WEAVING MODULE V ALIDATION In addition to automated traffic recorder counts and manual traffic surveys, video was recorded at San Francisco International Airport for a weaving section on the entrance roadways during peak traffic periods. From video observed during the 15-minute period beginning at 8:45 p.m. on August 3, 2007, the vehicles weaving from northbound and southbound US 101 to parking and curbside roadways were counted (see Figure D-1). It was noted that some conflicts occurred between weaving vehicles, although this effect was slightly obscured by downstream queuing on the arrivals curbside roadway. The weaving module of the QATAR model indicates that the weaving section operated at level of service (LOS) C, which is consistent with observations in the video, thereby validating the module results.


NB = Northbound SB = Southbound vph = Vehicles per hour


ACRP Report 40 Airport Curbside and Terminal Area Roadway Operations Appendix E SUMMARY OF FOCUS GROUPS This appendix presents the results of focus groups conducted with (1) airline passengers, (2) airport ground transportation staff, and (3) commercial ground transportation vehicle drivers and owners. These focus groups were conducted to obtain opinions regarding the airport curbside levels of service and the operations and physical factors that define those levels of service. At the beginning of each focus group, the moderator welcomed the participants, explained that the results of the focus group were to be used to support a federally funded research project concerning airport roadways and curbside operations nationwide, not the operations at a single airport. The moderator assured the focus group participants, particularly the commercial vehicle drivers, that their comments would be presented only in summary form and would not be attributed to specific individuals. A moderator’s guide prepared specifically for these focus groups, which included suggested questions, was used during all of the focus group sessions. Jacobs Consultancy slightly modified the guide after conducting the focus group sessions during the AAAE workshop to reduce the number of questions to be asked during the focus group sessions conducted at the AGTA meeting. The list of questions was also provided to JD Franz Research, Inc., and incorporated into the moderator’s guide used to conduct airline passenger focus group sessions. Unfortunately, the photographs of curbside levels of service that were used successfully during the airline passenger focus group sessions were not incorporated into the focus group sessions of airport ground transportation staff or commercial vehicle drivers. The airport ground transportation staff focus groups were scheduled for 90 minutes, with some lasting longer. The commercial vehicle driver focus groups were scheduled for about 60 minutes, with a few lasting about 75 minutes. FOCUS GROUPS OF AIRLINE PASSENGERS The research findings presented below were derived from four focus groups that were commissioned by Jacobs Consultancy on behalf of Airport Cooperative Research Program (ACRP) Project 7-02 and conducted by JD Franz Research, Inc. The focus group sessions were held on July 11 and 12, 2007, in California and on July 24, 25, and 26, 2007, in the Washington, D.C, metropolitan area.


Overview The first focus group session, held the evening of July 11, 2007, in Sunnyvale, California, was attended by 11 people. The second and third sessions, held the evening of July 12, 2007, in Fremont, California, were attended by 7 and 10 people, respectively. The fourth, fifth, and sixth focus group sessions, which were held the evenings of July 24, 25, and 26, 2007, in Bethesda, Maryland, were each attended by 10 people. All six groups consisted of airline passengers who travel at least four times per year. In recruiting potential group members, every effort was made to obtain a crosssection of passengers in terms of gender, numbers of trips, familiarity with area airports, types of travel, and age. Specific screening criteria were as follows: •

A mix of males and females

A mix of numbers of annual trips in the ranges of 4 to 6, 7 to 9, and 10 or more

Familiarity with at least two area airports (Oakland, San Francisco, and Mineta San Jose international airports in California and Baltimore/Washington International Thurgood Marshall, Washington Dulles International, and Reagan Washington National airports in the Washington, D.C. area)

Users of curbsides and curbside facilities

A mix of national and international travelers

A mix of business and leisure travelers

A mix of ages in the following ranges: 18 to 24, 25 to 34, 35 to 44, 45 to 54, 55-64, and 65 and older, with the understanding that the youngest and oldest age groups would be less likely to be eligible for participation in the focus groups

Those working in the marketing profession; those employed in the travel industry, by airport operators, or by airlines; recent focus group participants, and those expressing extreme or uncaring views were screened out. The primary purposes of the focus groups were to determine what airline passengers want regarding airport curbsides as well as what they like and dislike about existing facilities. Specific areas of inquiry included the following: •

Introduction of participants and study

How people usually get to the airport

The extent to which they use curbside facilities (screening and introductions)

E-3 •

Impressions of the curbside facilities at various area airports

Likes and dislikes about existing curbside facilities in the area

Particularly good facilities at other airports

What the ideal curbside would look like

Impressions of various curbside service levels

As needed, further inquiries focused on: •

Attitudes about double and triple parking

Attitudes toward multiple curbsides

Opinions about reserved spaces for public transportation

Feelings about lighting levels

Issues regarding air quality

Attitudes toward law enforcement personnel

Opinions about cell phone lots and free short-term parking

Because this research was qualitative rather than quantitative, it is not possible to generalize the results to the population from which the participants were selected. Thus, although this appendix does contain conclusions and recommendations, they should be viewed as tentative rather than definitive and subject to confirmation via quantitative research. Summary From the results of these focus groups, it would appear that airline passengers are remarkably consistent with respect to their desires and expectations regarding airport curbsides. Neither geography nor travel characteristics seem to play a role; the findings are essentially the same regardless of group location and type of passenger. Following are the research team's conclusions regarding how airline travelers view the curbside of the future. 1.

Curbside Sidewalk Layout

Curbs should be wide and spacious for four reasons: to provide a reasonably pleasant atmosphere, to prevent crowding that impedes mobility, to facilitate pedestrians’ ability to walk both between and into terminals, and to ensure that passengers are not at risk of being pushed into traffic. Curbs should be covered at a minimum, and ideally climate-controlled. Signage should be clear and prominent,

E-4 including directions to parts of the curbside, areas within the terminal, and various types of ground transportation. Lighting should be adequate to ensure safety. A curbside layout should be available on the Internet where travelers buy tickets. Such a diagram should also be available other places for those who do not have Internet access. 2.

Curbside Roadway Traffic Flow

Although passengers understand that airport traffic will be dense, they expect it to be organized rather than chaotic. Ideally, two law enforcement officers would be present at the curbside: one to direct traffic and one to guide vehicles in to the curbside spaces. Law enforcement should be strict but not unreasonable. In addition, law enforcement officers should be polite and not arbitrary. To improve traffic flow further, passenger drop-off and pickup should be organized. Those individuals picking up airline passengers would appreciate the following: cell phone lots, free or reduced-rate short-term parking, and dedicated passenger pickup lots. Doorways or pylons at which passengers can be picked up should be near exits and baggage claim and should be clearly marked with numbers, letters, or colors. Arrivals and departures should be on separate levels; there might even be a third level for public transportation vehicles. If there are only two levels, there should be a separate island for buses, shuttles, taxicabs, and the like. Multiple traffic lanes would ensure that drivers who want to pull over can do so and that drivers who need to pass can do so as well. If double parking is permitted, it should be controlled by traffic officers; triple parking should not be allowed. 3.

Pedestrian Access

Although there was almost universal agreement among the focus group participants that a separate curb should be provided for the broad array of public transportation vehicles—from buses to hotel courtesy shuttles to taxicabs—there was also widespread concern about pedestrians crossing multiple lanes of traffic. Signals and traffic officers were viewed as providing a modicum of safety, but at the same time, impeding traffic flows; overpasses and underpasses were viewed as being particularly safe, but also potentially difficult to navigate. As a result, no consensus emerged on this topic. Perhaps the most intriguing idea, which is similar to the design of some railroad stations, was for stairwells and escalators to be connected to moving underground walkways that would deliver people to the correct island.

E-5 One other request was that all rental car companies be in the same facility, ideally across the street from the airport. Although the latter seems particularly suited to smaller airports, it was requested at larger ones as well. Finally, participants suggested that rental car shuttle buses be targeted to airlines rather than being specific to rental car companies so that multiple stops could be avoided. The practicality of this suggestion may merit further consideration. 4.

Handicapped Access

At present, the number of designated spaces for private vehicles transporting the handicapped is inadequate. There are also too few curb cuts for wheelchairs. Finally, it is not always clear from curbside signage where wheelchairs are available. The ideal curbside would be substantially more accessible to the handicapped. 5.

Baggage Check-in

Curbside baggage check-in facilities should be adequately staffed with competent and knowledgeable personnel. Lines should not be too long, and there should be neither a charge nor the expectation of a tip. Electronic check-in kiosks should be installed outdoors as well as indoors. Finally, one somewhat futuristic participant suggested that bags should simply be chipped so they could be dropped off and forgotten. 6.


Helpers should be available at curbside to provide assistance with baggage, the elderly, and children for departing passengers and to provide transportation information and guidance for arrivals. Curbside personnel should also be available to make sure that access to public transportation vehicles is organized. Baggage carts for those preparing to depart should be available at the curb, and they should be free. Besides being an amenity, it would improve the flow of passengers. Pay telephones should be available for those whose cell phones have died and who need to call drivers or public transportation providers. There should also be adequate seating for those who are waiting to be picked up. Activities for children or playgrounds should be available. Finally, several people suggested a free nicety, such as water or coffee (or in a few cases, wine or liquor). 7.

Electronic Signage

A number of suggestions were made for electronic signs on approaches to the curb and at curbside. These included departure gate listings, flight status reports, level of traffic congestion advisories, and wait times for check-in. Any or all of these may have sufficient merit to warrant further study.



Exemplary Airports

Airports that were viewed by multiple groups as having exemplary curbside operations included Denver International, Las Vegas McCarran International, John Wayne (Orange County), and Phoenix Sky Harbor International airports. Reasons for these selections were as follows: Denver International Airport – Spacious – Not congested – Flows well – Designed for growth – Good signage – Multiple islands for mass transit – Two lanes between islands, one for drivers to pull over and one for drivers to maneuver around those who are pulled over – Cell phone lot that is easy to get to − Doors for pickups clearly designated Las Vegas McCarran International Airport – Simple design – Flows well – Connectors make it easy to get around – Two levels – Good signage – Staff present to give directions – Good curbside check-in with no lines – Different exit doors for different transportation modes – Dedicated passenger pick-up lot – Reasonably priced metered parking – Short-term parking garage − All rental car companies are in the same area John Wayne Airport – Two levels − Drivers can dwell at the curb to pick passengers up Phoenix Sky Harbor International Airport – Large and well-designed – Wide roadways – Each airline has its own facility – Good shuttle pick-up − All rental car companies in a single place Those considering the curbside design of the future may wish to tour these airports in order to determine in more detail why these features are so appealing to passengers.


FOCUS GROUPS OF AIRPORT GROUND TRANSPORTATION STAFF To maximize the number of participants in these focus groups, they were conducted during two conferences that regularly attract many airport ground transportation staff. These conferences were the: •

American Association of Airport Executives (AAAE) Ground Transportation and Landside Management Workshop held in Phoenix, Arizona, on November 6-7, 2006

Airport Ground Transportation Association (AGTA) Spring Meeting held in Fort Lauderdale, Florida, on March 21, 2007.

At each conference, the conference sponsor introduced a representative of the research team who explained the purpose of the Airport Cooperative Research Program in general and ACRP Project 7-02 in particular, and then invited the conference attendees to participate in the focus groups. Over 90% of airport ground transportation staff attending each conference agreed to participate in the focus groups. More than 25 airport ground transportation staff participated in the focus groups held during the AAAE workshop. These staff included representatives from the airports serving Atlanta, Calgary, Charleston, Dallas-Fort Worth, Denver, Detroit, Greensboro, Houston, Las Vegas, Little Rock, Los Angeles, Memphis, Orange County, Phoenix, San Antonio, San Francisco, and Seattle, with several airports represented by more than one staff member. These individuals were assigned to one of three concurrent focus groups by airport size—large, medium, or small hub. Each group was moderated by a Jacobs Consultancy staff member who led the participants through a series of open-ended questions and tape recorded the discussions. More than 30 airport ground transportation staff participated in the focus groups held during the AGTA meeting. These staff included representatives from the airports serving Asheville, Atlanta, Birmingham, Charleston, Chattanooga, Chicago, Dallas (Love Field), Dallas-Fort Worth, Denver, Detroit, Fort Myers (Southwest Florida), Halifax, Little Rock, Miami, Minneapolis-St. Paul, New Orleans, San Francisco, Tampa, Toronto, and Winnipeg, with several airports represented by more than one staff member. These individuals were assigned to one of three concurrent focus groups, generally, but not rigorously, by airport size (e.g., large, medium, or small hub). Each group was moderated by two Jacobs Consultancy staff members who led the participants through a series of open-ended questions and tape recorded their responses. Two of the participants in the focus groups at the AGTA meeting had attended the focus groups at the prior AAAE workshop and these individuals were asked to assist the focus group session moderators rather than participate in the focus groups. The findings and conclusions from the airport ground transportation staff focus groups are provided in combination with the findings and conclusions from the ground transportation vehicle drivers and owners focus groups presented in the next section.


FOCUS GROUPS OF COMMERCIAL GROUND TRANSPORTATION VEHICLE DRIVERS AND OWNERS A focus group of the owners and senior managers of airport ground transportation service providers was conducted during the AGTA meeting in Fort Lauderdale on March 21, 2007. This focus group consisted of 10 participants (two from one company) whose companies operate at the airports serving Chicago, Dallas, Fort Myers (Southwest Florida), Los Angeles, Milwaukee, New York (Kennedy and LaGuardia), Norfolk, and Washington, D.C. This focus group was moderated by four Jacobs Consultancy staff with support from an airport operator. Focus groups of the drivers of taxicabs, parking shuttle buses, and on-demand shared-ride vans (SuperShuttle) and traffic control officers were conducted at Washington Dulles International Airport on July 23 and 24, 2007. Focus groups of the drivers of taxicabs, on-demand shared-ride vans, and courtesy vehicles serving hotels/motels and off-airport parking lots were conducted at Oakland International Airport on August 30, 2007. Five separate focus groups were conducted at Washington Dulles International Airport with the participants organized by type of ground transportation service. One focus group was held with airport parking shuttle bus drivers (seven participants; not all participants were able to remain for the entire session), two groups consisted of SuperShuttle drivers (one group with eight participants and a second group with six participants), and two groups consisted of taxicab drivers (each group had eight to ten participants). Informal meetings were also held with three traffic control officers. Each commercial vehicle driver focus group at Washington Dulles International Airport was moderated by a Jacobs Consultancy staff member who tape recorded the results and comments. Four separate focus groups were conducted at Oakland International Airport. Again, the participants were organized according to the type of ground transportation service they operated. The first group consisted of five hotel/motel courtesy vehicle drivers, the second group consisted of five off-airport parking lot courtesy vehicle drivers, the third group consisted of nine on-demand shared ride van drivers, and the fourth group consisted of six taxicab drivers. Each of these focus groups was moderated by two Jacobs Consultancy staff members who led the participants through a series of open-ended questions and tape recorded their responses. FINDINGS AND CONCLUSIONS OF AIRPORT GROUND TRANSPORTATION STAFF AND COMMERCIAL VEHICLE DRIVERS AND OWNERS FOCUS GROUPS 1.

What is the purpose of an airport terminal curbside?

Most airport ground transportation staff indicated that the primary purpose of an airport terminal curbside is to serve as the transition point between surface access modes and the airport terminal, namely the point where customers enter or exit a ground transportation vehicle. Others indicated that the curbside should (a) facilitate the movement of passengers and visitors into and out of the terminal area (including

E-9 the movement of pedestrians, private vehicles, and commercial ground transportation vehicles), and (b) welcome visitors and returning residents to the community and accommodate private vehicles and commercial vehicle operations. Airport ground transportation staff also stated that the purpose of a curbside was to serve as a “point of sale” where commercial vehicle drivers and other company representatives greet arriving customers and help them select a travel mode. Thus, visibility and proximity to the exit doors were mentioned as key considerations by drivers and owners. 2.

What does the traveling public expect when they approach a departures (drop-off) curbside? An arrivals (pickup) curbside?

Airport ground transportation staff indicated that travelers expect efficiency, courtesy, timeliness (relative to on-time performance by scheduled ground transportation providers and minimal waiting times for on-demand transportation providers), accessibility, security, and friendly service. Some airport staff felt that travelers expect increasing levels of congestion at busy airports such as LaGuardia. Other airport staff felt that travelers expect to (a) readily find the desired ground transportation service (good signage and visibility), (b) encounter short walking distances, and (c) have weather protection. On the departures level, it was stated that travelers expect to find skycap service and “open” curb space that is not reserved for specific vehicles or transportation services. On the arrivals level, travelers expect to find space near their baggage claim area and to be able to quickly get in and out of the curbside area. Commercial vehicle drivers and owners also felt that travelers expect to find the desired service easily and quickly enter (or exit) the airport terminal area roadways. Many comments were made about the need for good signage. It was also recommended that there should be clearly designated spaces for buses (and other large vehicles). 3.

What do commercial vehicle drivers expect when they approach a departures or arrivals curbside?

Airport ground transportation staff felt that commercial vehicle drivers expect fairness (i.e., a level playing field), clear guidelines (rules and regulations) describing how they are allowed to operate, curb space reserved for their use (particularly for passenger pickup), and accurate flight information displays. Some airport staff indicated that commercial vehicle drivers/owners expect the airport operator to make their business “successful.” Commercial vehicle drivers and owners also described a need for reserved curb space locations, sufficient operational space for large vehicles, safe areas (no pedestrian crossings in front of commercial vehicle zones), covered boarding areas, easy (congestion free) access and egress, and clear signage. Some drivers requested

E-10 that the airport operator inform them of the rules and regulations and enforce these rules and regulations fairly. 4.

What do [you think] airport operators expect (or need) from a properly functioning curbside?

Airport ground transportation staff expect traffic to move efficiently, few queues of vehicles or pedestrians, and no drivers out of their vehicles (no unattended vehicles). At least one participant felt that airport management places a higher priority on parking and considers ground transportation operations and curbsides to be a lower priority. Few airport ground transportation staff addressed this comment. It was not included in the moderator guidelines for the focus groups held during the AAAE workshop. Commercial vehicle drivers and owners indicated that airport operators need to provide more curb space and to provide a separate but consolidated area for commercial vehicle passenger pickup where vehicles can enter and exit easily. 5.

What are the characteristics or metrics that indicate that a drop-off or pickup curbside is operating satisfactorily?

Airport ground transportation staff had difficulty identifying the characteristics that indicate that a curbside is operating satisfactorily. They were unable to reach consensus on the amount of delay or length of queues they considered acceptable (or unacceptable) as both vary by customer and type of ground transportation service. Several staff indicated that the key indication of satisfactory operation was not receiving any (or few) complaints from senior airport management or others. Other staff indicated that they relied on comment cards, looking out the window, or the number of people waiting at the curb to determine satisfaction. Commercial vehicle drivers addressed topics such as clear signage for customers, allowing shared-ride and taxicab starters to be positioned in a location to greet potential customers, and not requiring commercial vehicle passengers to cross a roadway. Taxicab drivers discussed control of line-jumping by taxicab drivers, placing the taxicab hold lot closer to the terminal (to improve response time), and allowing drivers to leave their vehicles unattended while they assist elderly or disabled passengers. They also suggested posting signs showing fares to major regional destinations. 6.

What are the characteristics or metrics that indicate that a drop-off or pickup curbside is not operating satisfactorily?

Similar to the response to Question 5, airport ground transportation staff did not identify specific characteristics or metrics that indicate when a curbside is not operating satisfactorily. Some airport ground transportation staff indicated that

E-11 they relied on the number of complaints they received to determine dissatisfaction. Others suggested that long vehicle queues that prevent or severely delay motorists from getting to their drop-off (or pickup) point are a good indication that a curbside is not operating satisfactorily. There was no consensus as to the amount of delay that is unacceptable, as it varies from airport to airport, by type of ground transportation service, and from departures to arrivals curbsides. One airport ground transportation staff member indicated that loading of passengers in the third lane is an indication of unsatisfactory curbside operations. Another indicated unsatisfactory conditions occur when police prevent motorists from stopping at the curbside and require them to recirculate or enter a parking facility. Another staff member confirmed that the Highway Capacity Manual does not apply to curbside areas and suggested that a combination of length of queue, delay, and dwell time could be used as a metric. However, this staff member also stated that few passengers complain about curbside congestion and expect to wait (particularly at large airports). Commercial vehicle drivers discussed their preference to separate private and commercial vehicles on the pickup curbsides and a dislike for narrow sidewalks. They also discussed the problem with illegal solicitation or “hustling” of passengers. They indicated a preference for passenger waiting areas that provide shelter from the weather and wind protection. 7.

Which airports have the best curbsides?

Among the airports that were considered to have the best curbsides were those that (a) physically separate private vehicles from commercial vehicles through the use of multiple levels or separate zones or courtyards, (b) provide good signage, and (c) provide a sense of openness. Those that were frequently cited as being the best were Denver International Airport (frequently mentioned) and the airports serving Atlanta, Orlando, Pittsburgh, and Toronto, which are among the newest airport terminals in North America. The Denver airport was mentioned as having good signage. Los Angeles and Fort Lauderdale-Hollywood international airports were mentioned as having good operations, and being clearly laid out, particularly considering the volumes of passengers served at Los Angeles International Airport. Other airports mentioned more than once included those serving Charleston, Terminal D at Dallas/Fort Worth International Airport (compared with the other four terminals at this airport), Las Vegas (particularly the taxicab queues), Ottawa, Sacramento, and Barcelona. Commercial vehicle owners cited the City Bus Center at Chicago O’Hare International Airport as an example of a good commercial vehicle curbside. Taxicab drivers in the focus group at Dulles preferred Baltimore/Washington International Thurgood Marshall and Reagan Washington National airports because the hold areas are closer to the terminal buildings and the passenger boarding areas are covered.

E-12 Courtesy vehicle drivers in the focus group at Oakland International Airport cited Lambert-St. Louis and Hartsfield-Jackson Atlanta international airports as examples of airports with good curbsides because hotel/motel and off-airport parking courtesy vehicle operators can lease curbside space and these airports have designated spaces listing the names of their services. The Oakland International Airport taxicab drivers focus group also mentioned Portland International Airport (Oregon) because of the availability of numerous customer service agents employed by the airport operator. Taxicab drivers also referred to Las Vegas McCarran International Airport as a good example of a taxicab passenger boarding area and queue. 8.

Which airports have the worst curbsides?

Among the airports that were mentioned as having the worst curbsides were those that were perceived as being cramped or dingy (e.g., Miami International Airport), having poor or confusing signage, mixing private and commercial vehicles, and having poor pedestrian circulation. The airports mentioned included Washington Dulles International Airport (because of the limited number of exit doorways leading to the arrivals/pickup curbside, narrow sidewalks, and crosswalks leading across the commercial vehicle lanes), Chicago O’Hare International Airport, Edmonton International Airport, Bush Intercontinental Airport/Houston, and Seattle-Tacoma International Airport. Las Vegas McCarran and Pittsburgh international airports were mentioned as being among those with the worst curbsides, as well as among those with the best curbsides. Commercial vehicle owners referred to Seattle-Tacoma International Airport (because the pickup area is in the garage and requires multiple level changes) and Dallas/Fort Worth International Airport (because of the number of terminals and confusion). Both the commercial vehicle owners and drivers cited Bob Hope Airport in Burbank, California, as an example of poorly configured and undersized curb space. 9.

What is your perspective of [the following topics]:

Many of the focus groups were unable to address all of the following topics because of time constraints. a. Double or triple parking along the curbside? Airport ground transportation staff responded that: (1) motorists will double or triple park when they are delayed finding a curbside space, and (2) commercial vehicle owners dislike double and triple parking because it prevents them from accessing designated passenger boarding areas. b. The public’s preference for the inner versus outer curbside? Airport ground transportation staff responded that having inner and outer curbsides is expensive because it requires more real estate (and wider structures at airports having upper and lower level roadways). Commercial

E-13 vehicle owners and drivers would prefer to be able to pick up customers near the terminal entrance and allow their customers to avoid having to cross roadways. Taxicab drivers in the Oakland International Airport focus group felt that providing a convenient walk between the terminal and taxicab boarding area was more important than if the boarding area is at the first, second, third, or fourth curbside. (Oakland International Airport has five parallel curbsides.) c. Reserving space for high occupancy vehicles or public transit vehicles? Some airport ground transportation staff felt it was okay if all commercial ground transportation vehicles are treated fairly. Another commented that curb space for public transit vehicles should be located in areas that no other commercial vehicle is using. Only one focus group participant stated that preserving space close to the terminal doors was important, but this individual also felt that this space should be at the end of the curb rather than in the center. Instead of just discussing reserving space for high occupancy vehicles or public transit vehicles, two focus groups discussed factors they considered when allocating curb space. These factors included consideration of revenue generated to the airport, vehicle size, volume of passengers transported, who complains the most, response to requests from local transit agencies, amount of pollution/emissions generated by the vehicles, and first in/first out provisions. d. Pedestrians crossing curbside roadways Many airport ground transportation staff described pedestrians crossing curbside roadways as a problem. Use of traffic control officers was a concern because of labor costs. Some stated that pedestrians prefer not to use underground tunnels unless they are forced to do so. Pedestrians do not always obey signals and frequently jaywalk. Pedestrians walking across the roadway near the taxicab stands is a significant issue at Washington Dulles International Airport because of the number of exit doorways and the contractor responsible for traffic control at the time the focus group sessions were held. (This contractor has since been replaced.) The commercial vehicle drivers discussed their concerns with safety and with pedestrians not obeying signals or traffic control officers. e. Use of traffic control officers versus signals to control pedestrians? Airport ground transportation staff indicated that it is hard to find the right balance between being nice (lax enforcement) versus improving traffic operations (stricter enforcement). Communicating with passengers,

E-14 appearance/uniforms, and the appropriate level of customer service were other issues mentioned. Commercial vehicle drivers discussed their concerns with the lack of enforcement of hustlers and the need for vehicle inspections (to ensure that limousine drivers have manifests). At Dulles, the comments offered by the commercial vehicle drivers reflected the poor performance of the thencurrent traffic control officers (or flaggers).


ACRP Report 40 Airport Gurbside and Terminal Area Roadway Operations





Preface This resea.rch was conducted by JHK & Associates as National Cooperative Highway Researeh Program (NCHRP) Project 3-28, Phase I. the Traffic Institute at Northwestern University served, as suþcontractor on the project. I\,fr. William R. Reilly of JHK & Associates was hincipa.l Investigator, and the prineipa.l pnofessional for the Traffic Institute s,as Ùto. Ronald

sections, Transit, a¡d Pedestrians.. Develo¡m.ent of these:sections,has been carried out a.s part,of NCÍIRP Project 3-28¡ l'Development of an lrproved Highway Capacity À[anual:" .Froject 3-28 wa.s sta¡ted ít t977, and the final report on Phase;I of the Project-v¡as

C. Pfefer.

team meqnbers were James H. Kell, RueI H. Robbins, Richard A. Presby, artd Iris J. Fultrerton of JHK & Associates. Technical editor of these materials was Iúr. Ù¿vid A. KelI of JIII( & Associates --who also served as production superwisor during ffua1 layout and paste-up. For the Tbaffic Institute, Jack Hutter, Alex Sorton, and Rober.'.t Seyfried provided valuable input to the work. Other personnel in both agencies also.contributed to the

Other key




Appreciation is extended to the Tra.nsportation, Research Board's Csmittee on Highway Capacity.and Quality of Service for their cooperation in surveying users, for conducting workshops at the 1978 Annual Meeting of the Tranq)ortátion Resesxeh Board and for reviewing these-interim materials prior to publication.

Contents AMLYSIS










description of the calculation; aQd several numerica.l examples are .provided... Completed calculation forms are.provided: and shown'for eaçh example. AIso, a blank fom is provided in each section, except for the rrTraflsit" material, which does not utilize a calculation form. j

Special acknowledgÊ-rnent is dú.e .to tsro individuals. Mr. Herbert l-evinson of Wilbur fuúth, and Associates served as principal. a.uthor of the lransit section,, ¿nd Mr. Jeffney Zupan of the Regional Plan Association contributed the ba.sic wôrk leading up to. the Pedestrian seetion of these i¡terim nøteria1s. The NCIIRP Prcject 3-28 Pane1 played an iræortant part in guiding the research, and took an a"etive role as "userS" in providing insights and suggestions on the contents and format of the i¡terim sections included in this voh¡rp.


submitted to NCHRP in August, t979. The',fihal report d,êscribris the..t¡ser surveys; the assesgænt of reSeanch and literature,..'the proêess usèd for devetr-oping t.te interi-m Ea;terials incLuded herê, and the' proposed research, program needed to prioduce, docr.uÍentation for a new Higbrrayr Gipacfty ìfanuâl. of the interim materiatrs in ttris report is introduced with a "DISCUSSIONU wtrioh eplains the background and, the conceptual framework..for the teehnique. The technique itself is ex¡plained'and references are cited. The "USER APPLICATIONS" section then leads.the user through a step-by-step

-l . , Cr.itical Mgvement based on wark conducted in the 1960's and 19?O's by various researchers and praetilioners-. .Of partí-cu1ar' irryortance are ttre q,orks of !úclner.ney and Peterden, and of Messer and Fambro. The project team did, however', make major changes in previously reported methods to devise the final technique as presented herein. Mr. Willian R. Reitty, Principal Inqestigator of. NGBP Project 3-28; had'primary responsibility fqr derivilg the final proced,ure,.' CrítícøI Movement AnøIyeis



Analysis a.lloup ;the,I{Cld,user

to analyze the wban signalized intersecttotr,&s â,nr .entire uni!¡:.:. The overall,;intersee.tion,::LeveL of service and. the effects on, Ievel of.serviqe of desi-gn and operational cllanges':cg4 be deternined¡ A1so, guidelines on .ranges, of vehiele-.delay eNpeoted under dif ferent .Ievels of .servÍce are included¡:,The.. technique is divided into P[-Âl,lNIlG applications for relatively simple and quick computations; and OPBATIONS ÁND DESIGN applications for a more detailed solution. Both epplications a¡e similar in concept and both allow the user to analyze intersections operating with pretimed signqls..,' vetricle actueted signals, and multiphase signals ..,,: .r.ii.. with pfuse .oveflap." ,r For dete¡nination of . capaçity orr lev.e1.,,.gf senvice of.,, a si¡gJ.e intersection ',. the:1965 HCIÁ remains the pr;ingipal tool until:tþe ¡en,,HOÍ is. ,:.



This report comprises the first se¿ of interin materials which will be distributed prior to the publication of a new 'rHlghway Capacity ìÍanr¡al" in the nid 1980rs. These interim materials are intended for application by HCM users in the 1980-1982 period. A user resporse fom is included at t¡e end of this dæLtent to permit users of these m¿teri¿ls to corrnunicate their comments to the Transportetioo Resea¡ch Board directly. This trser response will be vital in identifying desirable revisions to the interim materials prior to their inclusion i¡ the new ma¡ual. Users are encouraged to send to TBB thej¡ observations, including actual data and analyses. The interim materials provided i¡ this section Unsignalized Interare C?itical @_¡nafnlg,


: .. : Intersectíons .; :





: r :, ì-:

:. :.

for analypis,of qlsiepalized intersections"is an adaptalio.n, in content ênd f ormat, of a Germa.n .technique çeported in ,the Organisatiq+.for Econ'omi-c Co-Operatj-on and, Develo¡xrent . (OECD), repor,t, . "Cap4-eity of At{rade Jr¡nçtions." Mr. J¿nes Er,$eltrr qf,'the ÌGIRP koject 3-28 team, was most directly-'reçpo.ns.ible .for revising and adapting.. lhis tecþnique tq; the ,point where it can be oJ use þ the H0[;user. ,' The procedr:rè


Only those unsignalized intersections that are controlled by two-way SIOP signs or by YIH.,D signs can be analyzed by this technique. The procedure is not aoolicable to uncontrol

ty or


flow of

vetricles in,passengçr .car calculated. for eaçh minor approach npveurent.¡ These values are

then gompared to the êxisting demand for each and the probable,delay and level of service


is estiqiated The assunption is rpde that trajor street traffis is r,¡ot aff,ected by ttre sÉnor street rrcvdnents. tr€ft turns from the major: street to'the ninor. street are influenced orÌly by the opX¡osing.najor street through flov¡. Minor street flovts; however, impeded by all other conflicting rnovêments. The proceduire inc1udes..,adjustinents fof mutual interference to the Itrinor. strêet traffic streams,. such as the additionaL !

adverse,...effect oif main str:eet vehicles waiting to maker.left turns. . In order to tt@t these potential jmpedences, it

is necessary,to,structure the computational. proced'ures and deal. with individual traffÍc


jJr ttre foLlowilg order,:

1. Right turns into the nqjor road; 2. I-eft turns frør the major i Ð?

Step 5. Assígn Lone Yolumes, ín vph

Step 7. Swn oJ Crítícøl Volumes

+ =-vph

Step 8. Intersectíon Level Servíce

1=IN lo


ãl G,I

ol o-l

Æ +




¡ as'l ezJ e¿ L er






Critical Movement Analysis: PLANN ING Calculation Form 1




Lltqolru eN¡ Cant¿ee"r



Step 4. Left Turn Check

Identífy. Løne







lb 6o


.55 .45 .ß


l59o 91o )3o

in vph c. G/C Ratio d. Opposing volume

in vph e. Left turn capacity on green. in vph

l. Left turn capacity in vph


g. [-eft turn volume

in vph h. Is volume





























Step 7. Sum oJ Crítícal Volumes _12Ç_.__*g__._3ø5_. 1o

Approach 3


= l3lo

!? zo

lru ld

lo lô

lå sl -l*ll 'l

¿y= 5o rn = l5l0

sl I ll


Approach 4


lr-r lJ F







(compare Step 7 with Table 6)






Step 9. Recalculate Aop LT LlNrs ro e lso.* .À'ppßD^¿RÉr Ceomet¡ic Change Signal Change

Volume Change

Approach 4

Step 6a: Críticøl Vt ' (two phase sígnal)





l-. l

N o o o CL







¡ ao'l ezJ e¿ L er


Step 8. Intersectíon Servíce

+J-c to


6b. Yolume Adjustmenttor

¡n = 04o




Step 5. Assígn Lane Volumes, ín vph

Step 2. Idenlíjy Volumes, ín






-5:=o F'''

Multiphase Sígnal Overlap Possible Volùme Adjusted Probable Critical Carryover Critical Phase Volume to next Volume phase in vph in vph

Approach a. Number of change intervals per hour b. Left turn capacity on change interval,


Ce,r¡ L1- BE HÀNDLeD w rrtt Z ò

PfOblem Stateme¡f Frru errsr¡ur- L05. Step


Comments *Not= TH^T LEF-' ruÈN D.=¡lAñù FoÈ ÀPPÈoÀ¿-H 3 Ê4{/ALs 4PÂ-etTç

Critical Movement Analysis

PLANNING Applications: Example

For Approach 3, the left lane is assigned


tour volumes shown on Calculation Form I for an existing urban i¡tersection. The following three questions must be

Lane configuration and peak answered:

is the intersection leve1 of service? Can left turr¡s be hândled without installing What

of through and right turn traffic. Therefore, the left lane carries 165 vph (90 left turns plus the difference between 18O a¡d 255) and the rj-ght lane carries 255 vptr. For Apprcach 4, the left lane is assigned 385 pch, of which 240 pclr are due to left turn vehicLes. Table

an e>cclusive phase?

Servi ce A

Step 2. Identify Voh¡sÞs. Existing peak hour volumes (vph) are shown on Calculation Form 1. Approaches are numbered L, 2, 3, and 4, from the west, east, north, and south, rêspectively.

3. Identify Phasing. A two

operation exists.

phase signel

Step 4. LeftTurn Chech. A 90 second peak hour cycle length ijs used. Forty cyclas per hour tfures 2.0 left turns per cycleresult in 80 left turr¡s per hour nade on thechangeinterval. Addi-tional1y, left turns made througþ'opposing tra.ffic on the green interval, assr.uning a 0.55 G/C ratio for Approac,hes I and 2 and a O.45 G/C ratio for Apprrcaches 3 arrd 4 a¡e calculated by the. forrrula:



For all directions, the capacity for left turns is equal to or greater than left turn demand. Therefore, the two phase signal operation is adequate. l.Ioæ üråt for left turns frun Approach 3, dsnand and c¿pacity ar"e equal at 9O vph. StepiÞ.. Assign l-ane VoIurEs. For Approaches. 1 and 2, left turn volumes are assigned to the left tur¡ lanes and tirough plus right turn volunies are divided equally between the rønaining lancs. For Approaches 3 and 4, factors frqn Table 3 a¡e used to cqrvert 90 a¡d 1Z) left turns (with 530'vph and 330 vpfr opposing, respectively) to 180 and 240, pch, respectively. Thus, a total pch volu¡r¡e of 51O (from Approach 3) and 770 (from Approach 4) iê cornputed. On a per lane baSi-s, 2þ5 pch and ll85 pch', from.Approaches 3 and 4, respectively, are ccxnputed.

(in vph) lum of Critical


Two Three Phase Phase 900 855 1050 1000 1200 - 1140



Step 1. Identify l¿.ne Gewptry. Existing lane configuration is strown on Calculation Forn 1.

Level of Service Ranges




vL =



3. If left tu¡n lanes are added on þproaches 3and4 what chåriges, if any, nay be expected. in the Ieve1 of service?



pch, of nhich 180 pch is due to left turn vehicles. The right lane is a"Iso a.ssigned 255 pch, ccmprised


1. 2.













app l i


Four or more Phases 825 965 1


t37 5 1225


App'licatþns (in pch)

(del eted)

right la¡e is also assigned 385 pch, comprised of through'and right tura traffic; Thus, the left Iane carries 265 pþ (120 left turns plus the difference between 24O and 385) and the right lane


carries 385 wh. The per lane volumes are entered in Step 5 of Calcul¿tion Forrn 1. Step

6. Critical

Vohunes. C?iticalvolures for

phase AlA2', onAppnoaches I and 2, is 795 + 40 LT or 455 + 50 LT.. Use 835. CÏitical Volr¡res for phase A3A4 on ApproachëS3--and 4 is 255 + I20 LT or 385 +

90 LT. Use 475. These r¡oltr¡es are graphically

ii step-ã'õî-the Step







of Critical Volumes. The sum of is 835 + ig76 or 1310 Wh.

Step 8. Interseetion l-evel of Service.. Using Table 6, this value falls.within the range of 1201 to 1350 vph or Level of Sèrvice D for two phase signals. The left tùrns can be handled using the geometry shown and a two phase signal. Step 9. Rec¿lculate. To.deternine the effect on leve__1õFêñÏõ6õf addihg lèft turn lanes on ApÞrÞaches 3 and 4, reür:r to Step 1 and reconpute.



Critical Movement Analysis: PLANNING Calculation Form 1






PfOblem Statement Fr¡ro crlruae Step 1. IdentíJy Lane Geometry



Step 4. Lett Turn Check

a. Number of change intervals per hour b. I-eft turn capacity on change interval,

',"*"u hl{ l\ll

in vph. c. G/C


är* o

Ratio d. Opposing volume

3l .1---¡
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