Volume 3 Travel Demand Model Documentation and User’s Guide February 16, 2010
prepared by
Chattanooga TPO 2035 LRTP – Volume 3: Travel Demand Model Documentation & User’s Guide
TABLE OF CONTENTS 1.0 Introduction ........................................................................................................................... 1.1 Model Certification Process ......................................................................................... 1.2 Datasets Available ......................................................................................................... 1.3 Overview of Model Performance and Documentation ...........................................
1 1 2 3
2.0 Data Development and Review ......................................................................................... 2.1 Traffic Analysis Zones .................................................................................................. 2.2 Socioeconomic Data ...................................................................................................... 2.3 Updating Highway Network to 2007 Conditions .................................................... 2.4 Traffic Count Data......................................................................................................... 2.5 Screenline Locations ..................................................................................................... 2.6 Travel Surveys ...............................................................................................................
5 5 9 20 29 29 33
3.0 External Trips ........................................................................................................................ 3.1 External Model .............................................................................................................. 3.2 External Validation Adjustments ................................................................................ 3.3 External Validation Results .........................................................................................
35 35 39 39
4.0 Trip Generation..................................................................................................................... 4.1 Trip Generation Process ............................................................................................... 4.2 Trip Generation Validation Adjustments .................................................................. 4.3 Trip Generation Validation Results ............................................................................
41 41 42 45
5.0 Trip Distribution .................................................................................................................. 5.1 Trip Distribution Model Structure .............................................................................. 5.2 Trip Distribution Model Development and Validation ........................................... 5.3 Trip Distribution Model Results .................................................................................
47 47 48 51
6.0 Mode Choice .......................................................................................................................... 6.1 Mode Choice Model Structure for General Highway Assignment........................ 6.2 Mode Choice Model Structure for Exclusive HOV or Truck Lanes....................... 6.3 Mode Choice Model Structure for Time-of-Day Model ..........................................
55 55 56 57
7.0 Highway Assignment .......................................................................................................... 7.1 Highway Assignment Model Structure ..................................................................... 7.2 Development and Validation of Highway Assignment Model .............................. 7.3 Highway Assignment Validation Results .................................................................
59 59 59 60
8.0 Summary and Conclusions ................................................................................................. 67 8.1 Summary of 2007 Model Validation Observations .................................................. 67 8.2 Future Model Enhancements....................................................................................... 68
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TABLE OF CONTENTS (continued) Appendix A: Network Project Lists Appendix B: Technical Memorandum #1 Appendix C: Technical Memorandum #2 Appendix D: Technical Memorandum #3 Appendix E: 2007 Volume-to-Count Ratios Appendix F: User’s Guide
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LIST OF TABLES 2.1
Number of TAZs in TransCAD Model ..............................................................................
5
2.2
Regional Summary of Socioeconomic Data for 2035 LRTP Update............................... 11
2.3
Facility Type Codes............................................................................................................... 21
2.4
Area Type Codes ................................................................................................................... 21
3.1
Internal-External (IE) and External-External (EE) Percentage Splits ............................. 36
4.1
New Chattanooga Trip Production and Attraction Rates ............................................... 43
4.2
Special Generator Locations ................................................................................................ 44
4.3
Aggregate Trip Rates ............................................................................................................ 45
4.4
2007 Trips per Household by Trip Purpose ...................................................................... 46
4.5
Percent of Trips by Purpose................................................................................................. 46
5.1
Terminal Times ...................................................................................................................... 48
5.2
2007 Trips Between K-Factor Districts ............................................................................... 49
5.3
2035 Trips Between K-Factor Districts ............................................................................... 50
5.4
Penalties .................................................................................................................................. 50
5.5
Average Trip Length (in Minutes) ...................................................................................... 52
5.6
Intrazonal Trips by Trip Purpose........................................................................................ 53
6.1
Auto Occupancy Rates ......................................................................................................... 56
6.2
Vehicle Occupancy Allocation by Trip Purpose ............................................................... 57
6.3
Temporal Distribution of Trips ........................................................................................... 58
7.1
Volume Over Count Ratios by Facility Type, Area Type and Number of Lanes ........ 61
7.2
Comparison of Volume-to-Count Ratios by Screenline................................................... 62
7.3
Percent Difference for Daily Volumes (Calculated for Links with Counts) ................. 63
7.4
Root Mean Square Error (RMSE) by Volume Group ....................................................... 64
7.5
Vehicle Miles Traveled by Model Facility Type ............................................................... 65
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LIST OF FIGURES 2.1
TAZ Splits...............................................................................................................................
7
2.2
Regional Summary of Socioeconomic Data for 2035 LRTP Update............................... 11
2.3
Comparison of Households Between 2030 and 2035 LRTP Models .............................. 12
2.4
Comparison of Households Between All 2035 LRTP Model Years ............................... 12
2.5
Comparison of Population Between 2030 and 2035 LRTP Models ................................ 13
2.6
Comparison of Population Between All 2035 LRTP Model Years ................................. 14
2.7
Comparison of Employees Between 2030 and 2035 LRTP Models ................................ 15
2.8
Comparison of Employment Between All 2035 LRTP Model Years.............................. 15
2.9
Comparison of Hotel-Motel Units Between 2030 and 2035 LRTP Models ................... 16
2.10 Comparison of Hotel-Motel Units Between All 2035 LRTP Model Years .................... 17 2.11 Comparison of School Enrollment Between 2030 and 2035 LRTP Models ................... 18 2.12 Comparison of School Enrollment Between All 2035 LRTP Model Years .................... 18 2.13 Comparison of College Enrollment Between 2030 and 2035 LRTP Models ................. 19 2.14 Comparison of College Enrollment Between All 2035 LRTP Model Years .................. 20 2.15 2007 Model Network by Facility Type ............................................................................... 23 2.16 2007 Model Network by Area Type ................................................................................... 25 2.17 2007 Model Network by Number of Lanes ....................................................................... 27 2.18 Screenline Locations ............................................................................................................. 31 3.1
External Station Locations ................................................................................................... 37
7.1
Correlation of Assigned Versus Observed Volumes ....................................................... 63
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Chattanooga TPO 2035 LRTP – Volume 3: Travel Demand Model Documentation and User’s Guide
1.0 Introduction As part of Chattanooga-Hamilton County/North Georgia (CHCNGA) 2035 Long-Range Transportation Plan (LRTP) Update, the TransCAD travel demand model was updated and revalidated to the base year 2007 with a horizon year 2035. The first phase of the LRTP update includes the development and review of base year 2007 input data and validation of the model to base year conditions. Subsequent phases of this study include the forecasting of future year 2035 external trips, the preparation of an existing-plus-committed (E+C) network, and an evaluation of future travel demand within the CHGNGA Transportation Planning Organization (TPO) boundary. The TPO boundary includes all of Hamilton County in Tennessee and portions of Catoosa, Dade, and Walker Counties in Georgia. The validated 2007 model and CHCNGA 2035 transportation recommendations were utilized in the development of the CHCNGA Transportation Planning Organization’s (TPO) 2035 LRTP. The LRTP was conducted for the TPO housed within the Chattanooga-Hamilton County Regional Planning Agency (RPA) using a consultant team led by Cambridge Systematics. Cambridge Systematics developed and validated the base and future year model, while RPA staff developed the socioeconomic data for input into the travel demand model.
1.1 Model Certification Process The base year 2007 Chattanooga-North Georgia travel demand forecasting model uses procedures and model accuracy requirements consistent with state and national standards. National standards are documented in the Model Validation and Reasonableness Checking Manual coauthored by Cambridge Systematics for the Federal Highway Administration (FHWA). Effective March 1, 2008, the Tennessee Department of Transportation (TDOT) Long-Range Planning Division, Systems Planning and Policy Office implemented a Division Procedure for the MPO model approval process. On August 20, 2008, the TPO met with its consultants along with TDOT, GDOT, and CARTA to discuss the TransCAD modeling efforts for the CHCNGA 2035 LRTP Update. It was agreed at that time that the following four submittals would be provided to TDOT and GDOT as part of TDOT’s model approval process: 1. Outline of the model, planning assumptions to date, and model validation worksheet template; 2. Year 2007 and 2035 socioeconomic data files (TransCAD and GIS) for the TPO region, including any maps, graphs, charts, or tables developed as part of the TPO’s internal review; 3. Populated validation worksheet upon completion of draft validated model. This worksheet will include statistics for Trip Generation, Trip Distribution, Mode Choice (if applicable), and Traffic Assignment. If the assumptions included in submittal #1 change
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Chattanooga TPO 2035 LRTP – Volume 3: Travel Demand Model Documentation and User’s Guide
as part of the validation process, they will be documented and submitted for approval at this time; and 4. Full model documentation report and user’s guide, along with all TransCAD files, after the draft LRTP has been documented. Submittal #1 was submitted and approved by TDOT in September 2008. Subsequently, Regional Planning Agency (RPA) staff and its consultant, Cambridge Systematics, held a teleconference with the Georgia Department of Transportation (GDOT) and TDOT on June 30, 2009 to discuss the draft socioeconomic data and preliminary validation statistics, as outlined in this submittal. Submittal #2, which included the 2007 and 2035 socioeconomic data, was submitted to TDOT, GDOT, and the air quality Interagency Consultation Committee (ICC) in July 2009 and approved during the ICC meeting on August 6, 2009. Preliminary validation statistics were provided to the Interagency Consultation Committee (ICC) for review in advance of the September 3, 2009 ICC meeting. Submittal #3 was submitted to TDOT, GDOT, and the ICC on September 28, 2009. Comments were received by TDOT on October 8, 2009 and addressed via teleconference between TDOT and Cambridge Systematics on October 12, 2009. This full report constitutes Submittal #4, provided to TDOT and GDOT for review and approval in early December 2009.
1.2 Datasets Available Several datasets were created for the purpose of developing the 2035 LRTP, as well as for demonstrating air quality conformity for Particulate Matter (PM2.5). Air quality emissions are documented in the Conformity Determination Report (CDR) which constitutes Volume 2 of the three-volume LRTP series. Transportation projects included in each of the model networks are listed in Appendix A of this document. The following model datasets are available:
2
•
2002 – Used for air quality baseline emissions.
•
2007 – Base year validated model.
•
2009 – Used to compare with emissions in the State Implementation Plan (SIP) for PM2.5.
•
2015 Existing-Plus-Committed (E+C) – Used to determine what congestion would be in the year 2015 if no further transportation improvements were funded above and beyond what currently is in the FY ‘08-‘11 Transportation Improvement Program (TIP). Nonexempt (new road or widening) projects expected to complete construction by the end of calendar year 2011 are included in the E+C transportation network.
Chattanooga TPO 2035 LRTP – Volume 3: Travel Demand Model Documentation and User’s Guide
•
2015 Fiscally Constrained LRTP (Tier 1) – Includes all nonexempt projects funded for construction prior to or during year 2015 (Tier 1) of the fiscally constrained LRTP.
•
2025 E+C – Used to determine what congestion would be in the year 2025 if no further transportation improvements were funded above and beyond what currently is in the FY ‘08-‘11 Transportation Improvement Program (TIP). Nonexempt (new road or widening) projects expected to complete construction by the end of calendar year 2011 are included in the E+C transportation network.
•
2025 Fiscally Constrained LRTP (Tier 2) – Includes all nonexempt projects funded for construction prior to or during year 2025 (Tier 2) of the fiscally constrained LRTP.
•
2035 E+C – Used to determine what congestion would be in the year 2035 if no further transportation improvements were funded above and beyond what currently is in the FY ‘08-‘11 Transportation Improvement Program (TIP). Nonexempt (new road or widening) projects expected to complete construction by the end of calendar year 2011 are included in the E+C transportation network.
•
2035 Fiscally Constrained LRTP (Tier 3) – Includes all nonexempt projects funded for construction prior to or during year 2035 (Tier 3) of the fiscally constrained LRTP.
The above nine datasets have been provided to TDOT and GDOT as part of this Volume 3 submittal.
1.3 Overview of Model Performance and Documentation This technical report, which constitutes Volume 3 of the three-volume LRTP series, provides detailed information on the development and validation of the TransCAD travel demand model. Section 2.0 describes the data development and review process, including traffic analysis zones (TAZs) and highway network information. Section 3.0 describes the estimation of base year external trips. Section 4.0 provides information on the trip generation model while Section 5.0 explains the trip distribution model. Section 6.0 describes the mode choice model while Section 7.0 provides information on the highway assignment model. The report concludes with a summary and discussion of next steps and future model enhancements in Section 8.0. Section 8.0 also includes a summary bullet list of the overall model performance. Overall, the 2007 model is performing within acceptable limits with an overall volume-to-count ratio of 0.96 and a Root Mean Square Error (RMSE) of 34.6 percent.
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2.0 Data Development and Review Section 2.0 describes in detail the traffic analysis zone (TAZ) structure, socioeconomic data, highway network, traffic count data, screenline locations, and travel surveys.
2.1 Traffic Analysis Zones As part of the previous 2030 LRTP Update, the TPO converted the old MINUTP model to TransCAD and refined the TAZ structure significantly resulting in 445 total TAZs for the entire model region. After the 2030 LRTP was adopted, the TPO added more TAZs to Catoosa County as the remaining sliver of Catoosa County not in the previous model was added for the purpose of calculating emissions for air quality conformity. This addition resulted in a total of 450 TAZs for the entire model region. As part of this current 2035 LRTP Update, the TPO has further refined the TAZ structure by splitting internal zones mostly in the outlying regions of the model and within the downtown area of Chattanooga. Previously, the Enterprise South Industrial Park (ESIP) area was included within one TAZ. As part of this update, the ESIP TAZ has been split into eight TAZs based on the ESIP future site plan. In addition to splitting several internal zones, eight more external zones were added to the current model, as indicated in Table 2.1 below. All of these TAZ splits have resulted in a current total of 628 TAZs (590 internal + 38 external) in the entire model region, an increase of 178 TAZs, or 40 percent more zones. Maps illustrating the TAZ splits are attached.
Table 2.1
Number of TAZs in TransCAD Model
2030 LRTP Model
Expanded Catoosa Model
2035 LRTP Model
Internal TAZs
415
420
590
External TAZs
30
30
38
Total TAZs
445
450
628
The following criteria were used to determine if a TAZ should be split, when feasible: •
Greater than 15,000 productions per TAZ in 2030;
•
Irregular shaped or large sized TAZs;
•
Major existing or planned roads bisecting TAZ; and
•
Potential special generator located in TAZ (i.e., isolated TN Aquarium).
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Chattanooga TPO 2035 LRTP – Volume 3: Travel Demand Model Documentation and User’s Guide
The following guidelines were used to split the TAZ boundaries, when feasible:
6
•
Existing and future roadways;
•
Existing and future land use;
•
Railroads;
•
Water bodies; and
•
Census block group boundaries.
Chattanooga TPO 2035 LRTP – Volume 3: Travel Demand Model Documentation and User’s Guide
Figure 2.1 TAZ Splits
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Chattanooga TPO 2035 LRTP – Volume 3: Travel Demand Model Documentation and User’s Guide
2.2 Socioeconomic Data RPA staff developed the 2007 and 2035 socioeconomic data as part of the ChattanoogaHamilton County/North Georgia 2035 LRTP Update. Historically, the Coosa Valley Regional Development Center (RDC) has developed the socioeconomic data for the Georgia portion of the TPO. However, development of the socioeconomic data for the Georgia side has since become the responsibility of the TPO due to funding limitations. Year 2015 and 2025 socioeconomic data used to develop the Tier 1 and 2 models, respectively, were interpolated using 2007 and 2025 socioeconomic data and then adjusted in the Enterprise South area to reflect build-out of the Volkswagen manufacturing plant by model year 2015. Since model years 2002 and 2009 are used for air quality conformity purposes only, they are documented in the Conformity Determination Report constituting Volume 2 of the threevolume LRTP series.
Variables The socioeconomic data included in the TransCAD travel demand model can be broken in to four categories, as follows: •
Household Data – Includes total population, school-age children (population between ages 3 and 18), and total housing units.
•
Employment – Includes total number of employees and number of employees for each of the five employment categories: - Agricultural/mining/construction; - Manufacturing/transportation; - Retail; - Service; and - Government.
•
School Enrollment – Includes number of grade school students at the location of the school, number of university students at the location of the university, and total school enrollment (grade school students plus university students). University student enrollment includes community, technical, or vocational colleges and universities.
•
Hotel-Motel Units – Includes number of hotel-motel units.
Methodology The RPA collected the number of building permits issued between 2000 and 2007 for each of the four counties, geocoded their locations, and added the new building permits to the 2000 households by TAZ to achieve 2007 households. Population for the year 2007 was
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Chattanooga TPO 2035 LRTP – Volume 3: Travel Demand Model Documentation and User’s Guide
calculated by applying the persons per household ratio in each of the year 2000 zones to the total number of households in 2007. If a zone was split, the persons per household ratio from the parent zone in the year 2000 was applied for each split zone. However, subsequent logic checks determined that some manual adjustments were necessary in Dade and Hamilton Counties to reflect more reasonable persons per household ratios and thus, the overall persons per household ratio for the entire county were applied to those specific zones. The proportion of the total population attributable to school-age children was calculated using 2007 American Community Survey (ACS) data for each of the four counties, with the exception of Dade County, which utilized the same school-aged children factor in Walker County as ACS data was not available for Dade County. Building permit data for Hamilton County were acquired from the municipal building permit files, whereas building permit data for Catoosa and Walker Counties were acquired from The Market Edge, an information reporting service. Since building permits are not required in Dade County, electrical inspection records were acquired from the County as proxy for building permits. As part of the current 2035 LRTP Update, the RPA evaluated a number of sources for employment data as there were significant discrepancies in the employment control totals between the different data sources within the region. After careful review, it was determined that year 2007 ES202 employment data from the Bureau of Labor Statistics (BLS) be used. Previously, as part of the 2030 LRTP Update, RPA staff utilized the employment control totals from the Bureau of Economic Analysis (BEA) while using Dun & Bradstreet point data to distribute the BEA employment by TAZ. This previous method was used due to some of the suspect employment numbers in the Dun & Bradstreet data. Since then, it has been determined that the ES202 employment data is more comparable to other data sources and the BEA control totals for the year 2000 may have been overestimated. As a result, when comparing the 2000 employment to the 2007 employment, there is a significant decrease in employment from the year 2000 to 2007. However, as mentioned above, it is likely that the 2000 employment was erroneous. School enrollment data were collected from local school boards, the phone book, Internet, and applying local knowledge. The number of hotel-motel units were collected from the Visitors Bureau, in-house Geographic Information Systems (GIS) file, a field survey, as well as the phone book and the Internet.
Observations As indicated in Table 2.2, between the years 2007 and 2035, the Chattanooga region is expected to grow by approximately 39 percent in population and employment. Since the number of school-age children is decreasing in the region, school enrollment is only expected to increase by 16 percent. Although employment decreased from the year 2000 to 2007, as discussed earlier, employment does increase by 39 percent from the year 2007 to 2035, consistent with household and population forecasts. Figure 2.2 compares the regional
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summary of each socioeconomic variable between the years 2007 and 2035. As expected, all variables increase from the year 2007 and 2035.
Table 2.2
Regional Summary of Socioeconomic Data for 2035 LRTP Update Total Region 2007
2015
2025
2035
Percent Growth from 2007 to 2035
Households
178,557
199,570
225,878
252,148
41%
Population
425,724
473,614
533,492
593,335
39%
Employment
218,612
251,377
278,244
305,061
40%
Hotel-Motel Units
9,693
10,274
11,001
11,729
21%
School Enrollment
69,102
72,547
76,851
80,357
16%
College Enrollment
24,459
25,679
27,202
29,520
21%
Variable
Figure 2.2 Regional Summary of Socioeconomic Data for 2035 LRTP Update 700,000 600,000 2007
500,000
2015
400,000
2025 300,000
2035
200,000 100,000 0 Households
Population
Employment
Hotel-Motel Units
School Enrollment
College Enrollment
Households Figure 2.3 below compares the number of households between the previous 2030 LRTP (years 2000 and 2030) and the current 2035 LRTP Update (years 2007 and 2035). With the exception of the Georgia counties in the year 2030, the households increase for each year.
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Chattanooga TPO 2035 LRTP – Volume 3: Travel Demand Model Documentation and User’s Guide
Growth in Georgia is expected to slow down between the years 2007 and 2035 and it is expected that 2030 households in Georgia were overestimated during the previous LRTP update.
157,459
2000 2007 2030 2035
35,136
24,129
20,320
15,275
16,649
12,882
12,528
931
839
760
50,000
1,190
100,000
43,919
150,000
140,707
200,000
124,447
250,000
200,351
Figure 2.3 Comparison of Households Between 2030 and 2035 LRTP Models
0 Hamilton
Dade
Walker
Catoosa
County Note: 2030 expanded after 2030 LRTP Update to include all of Catoosa County.
140,707
200,000 150,000
200,806
157,864
250,000
179,351
Figure 2.4 Comparison of Households Between All 2035 LRTP Model Years
2007 2015 2025 2035
0 Catoosa
12
Dade
County
Hamilton
Walker
15,275
14,421
13,565
12,882
931
898
866
839
35,136
31,208
27,275
50,000
24,129
100,000
Chattanooga TPO 2035 LRTP – Volume 3: Travel Demand Model Documentation and User’s Guide
Population As indicated in Figure 2.5, population in Hamilton County increases each year, regardless of which LRTP update. However, Dade County population decreased from the year 2000 to 2007, even though the number of households increased. This is as a result of adjusting the number of persons per household ratio to more accurately reflect existing conditions in Dade County, which are more consistent with the other counties in the TPO region. In addition, it is suspected that the year 2030 population in the Georgia counties was overestimated during the previous 2030 LRTP as growth is expected to slow down in Georgia.
400,000 350,000
328,674
450,000
307,897
463,347
500,000
362,330
Figure 2.5 Comparison of Population Between 2030 and 2035 LRTP Models
2000 2007 2030 2035
62,244
52,955
38,575
42,085
32,666
31,749
50,000
2,354
100,000
2,140
2,460
150,000
3,837
200,000
88,058
250,000
114,556
300,000
0 Hamilton
Dade
Walker
Catoosa
County Note: 2030 expanded after 2030 LRTP Update to include all of Catoosa County.
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Chattanooga TPO 2035 LRTP – Volume 3: Travel Demand Model Documentation and User’s Guide
328,674
450,000 400,000 350,000
464,348
415,905
500,000
367,443
Figure 2.6 Comparison of Population Between All 2035 LRTP Model Years
2007 2015 2025
300,000
38,575
34,353
32,666
2,354
2,277
2,202
2,140
50,000
88,058
78,843
100,000
69,616
150,000
62,244
200,000
36,467
2035
250,000
0 Catoosa
Dade
Hamilton
Walker
County
Employment As mentioned earlier, the source of the employment data has changed since the previous LRTP and thus, there is a significant reduction in employees from the year 2000 to 2007 due to suspected overestimation in the year 2000. Year 2007 employment data was based on ES202 records from the BLS and was supplemented by records from the Chamber of Commerce, schools, motel in-house records, and job announcements from the newspaper. Year 2000 data was compiled from the Dun & Bradstreet database and was factored up to BEA employment control totals. BEA derived the employment data in part from the BLS data which accounts for about 80 percent of its employment data. The difference between the BEA data and the BLS data is attributed to BLS only reporting employment covered by the State UI and UCFE programs while BEA also estimates employment for farms, part-time employees, private households, schools, religious organizations, railroads, military, and international organizations. Since BEA data did not include addresses and the 2000 approach would exacerbate errors from misgeocoding and misreporting, the RPA decided to geocode the BLS data and supplement it with the additional sources mentioned above for 2007 employment. Figure 2.7 compares the new 2007 and 2035 employment control totals to the old 2000 and 2030 employment control totals. Due to the change in data sources, there are significant differences between LRTP datasets. However, it is suspected that the new 2007 employment estimates and 2035 forecasts are more accurate.
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Chattanooga TPO 2035 LRTP – Volume 3: Travel Demand Model Documentation and User’s Guide
250,000 200,000
2000
194,977
300,000
240,320
350,000
274,622
308,469
Figure 2.7 Comparison of Employees Between 2030 and 2035 LRTP Models
2007 2030 2035
20,040
56,598
15,284
26,302
8,363
27,904
8,243
195
516
331
50,000
108
100,000
21,465
150,000
0 Hamilton
Dade
Walker
Catoosa
County Note: 2030 expanded after 2030 LRTP Update to include all of Catoosa County.
250,000 200,000
276,463
251,404
194,977
300,000
226,326
Figure 2.8 Comparison of Employment Between All 2035 LRTP Model Years
2007 2015 2025
150,000
2035
8,363
8,326
8,276
8,243
195
165
132
108
20,040
18,349
16,643
50,000
15,284
100,000
0 Catoosa
Dade
Hamilton
Walker
County
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Chattanooga TPO 2035 LRTP – Volume 3: Travel Demand Model Documentation and User’s Guide
Hotel-Motel Units As demonstrated in Figure 2.9, several hotels were constructed in Hamilton County between the years 2000 and 2007. The number of hotel-motel units in 2007 actually surpassed those projected in 2030 as part of the last 2030 LRTP. It is anticipated that the growth in hotel-motel units in Hamilton County will slow down between 2007 and 2035, although it will still increase by 22 percent. Similarly, Walker County hotel-motel units increased in 2007 beyond 2030 forecasted levels. However, it is suspected that the growth in hotel-motels units in Catoosa County was overestimated for the year 2030 during the previous LRTP update and it is expected to slow down by the year 2035, as the RPA is uncertain of future growth in Catoosa County.
10,876
Figure 2.9 Comparison of Hotel-Motel Units Between 2030 and 2035 LRTP Models
8,885
12,000
2007 2030 2035
4,105
8,000 6,000
2000
6,851
10,000
0 Hamilton
Dade
Walker County
Note: 2030 expanded after 2030 LRTP Update to include all of Catoosa County.
16
Catoosa
620
1,073
608
570
233
37
18
0
0
0
0
2,000
200
4,000
Chattanooga TPO 2035 LRTP – Volume 3: Travel Demand Model Documentation and User’s Guide
10,000
10,876
9,453
8,885
12,000
10,164
Figure 2.10 Comparison of Hotel-Motel Units Between All 2035 LRTP Model Years
2007 2015 2025 2035
8,000 6,000
233
221
209
200
0
0
0
0
620
616
608
2,000
612
4,000
0 Catoosa
Dade
Hamilton
Walker
County
School Enrollment The number of grade school students in Hamilton County decreased from the year 2000 to 2007 as there were a number of school closings. However, school enrollment is expected to increase by the year 2035. As demonstrated in Figure 2.11, the growth in school students in Walker County was faster than expected resulting in far more students in the year 2007 than originally forecasted by the year 2030 as part of the previous LRTP update. Since the RPA is uncertain of future long-term growth, there is only a minimal increase in school students between the years 2007 and 2035 in Walker County. In Catoosa County, it is suspected that the 2030 forecasted school enrollment may have been slightly overestimated and thus, year 2035 forecasts are slightly lower when compared to the year 2030.
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Chattanooga TPO 2035 LRTP – Volume 3: Travel Demand Model Documentation and User’s Guide
58,718
2000 2007 2030
50,000
2035
14,770
7,083
7,523
0
0
0
0
10,000
5,111
3,931
20,000
7,042
30,000
11,225
40,000
14,116
60,000
50,835 54,092
70,000
51,570
Figure 2.11 Comparison of School Enrollment Between 2030 and 2035 LRTP Models
0 Hamilton
Dade
Walker
Catoosa
County Note: 2030 expanded after 2030 LRTP Update to include all of Catoosa County.
58,718
60,000
53,370
50,835
70,000
56,536
Figure 2.12 Comparison of School Enrollment Between All 2035 LRTP Model Years
2007 2015
50,000
2025 40,000
0 Catoosa
Dade
Hamilton County
18
Walker
7,523
7,832
0
0
0
0
10,000
7,393
7,042
12,484
11,785
20,000
11,225
30,000
14,116
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Chattanooga TPO 2035 LRTP – Volume 3: Travel Demand Model Documentation and User’s Guide
College Enrollment College enrollment in Hamilton County increased by 23 percent between the years 2000 and 2007. However, growth is expected to slow down by the years 2030 and 2035, as indicated in Figure 2.13. Since the last LRTP update, the TPO TransCAD model was expanded to include all of Catoosa County. As a result, Harvest Deaf Bible College in Catoosa County is now included in the model, which accounts for the 27 college students in the year 2007 not previously in the model. In addition, Covenant College in Dade County was not included in the previous LRTP update and has since been added to the model.
25,000 20,000
18,780
27,932
25,059
30,000
23,082
Figure 2.13 Comparison of College Enrollment Between 2030 and 2035 LRTP Models
2000 2007 2030 2035
15,000
35
0
27
0
0
0
0
0
0
5,000
0
1,350
1,553
10,000
0 Hamilton
Dade
Walker
Catoosa
County Note: 2030 expanded after 2030 LRTP Update to include all of Catoosa County.
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25,000
27,932
25,670
23,082
30,000
24,233
Figure 2.14 Comparison of College Enrollment Between All 2035 LRTP Model Years
2007 2015
20,000
2025 2035
15,000
0
0
0
0
1,553
1,501
1,417
35
30
28
27
5,000
1,350
10,000
0 Catoosa
Dade
Hamilton
Walker
County
2.3 Updating Highway Network to 2007 Conditions In order to update the year 2000 model network to the year 2007, a list of capacity-adding transportation improvements completed between the years 2001 and 2007 was developed and distributed to the ICC for review and approval. Maps of these projects and the corresponding list are included in Appendix A. These projects were coded on top of the previously validated 2000 model network to reflect 2007 transportation network conditions. In addition, several roads were added to the model network to more accurately depict travel patterns and to assist with splitting several of the larger traffic analysis zones (TAZs). TRIMS and Roadway Characteristics (RC) data were obtained from TDOT and GDOT, respectively, to assist with reviewing the link characteristics (facility type and number of lanes) in the model network. To supplement this information, several windshield surveys were conducted to obtain area type, facility type, and number of lanes data for those roads being added to the model. Maps of the 2007 model network by area type, facility type, and number of lanes are provided in Figures 2.15, 2.16, and 2.17 below. As part of the 2007 model update, a new area type code representing industrial land uses were added to the model. This new area type provided the ability to reduce speeds in areas serving industrial facilities. The TPO conducted a windshield survey in 2008, during which time areas representing industrial
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land uses were noted and revised accordingly in the 2007 model. In addition, topography data was overlayed on top of the 2007 model network to assist with updating the mountainous area type codes added during the previous model/LRTP update. A complete list of facility type and area type codes is included in Tables 2.3 and 2.4, respectively.
Table 2.3
Facility Type Codes
Code
Description
1
Interstate
2
Expressway
3
Principal Arterial, Divided
4
Principal Arterial, Undivided
5
Minor Arterial
6
Collector
7
Ramp
8
One-Way
90
External Centroid Connector
99
Internal Centroid Connector
Table 2.4
Area Type Codes
Code
Description
1
Central Business District (CBD)
2
Central Business District Fringe
3
Residential
4
Outlying Business District
5
Rural
6
Urban Undeveloped
7
Mountainous
8
Industrial
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Figure 2.15 2007 Model Network by Facility Type
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Figure 2.16 2007 Model Network by Area Type
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Figure 2.17 2007 Model Network by Number of Lanes
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2.4 Traffic Count Data The validation of any travel demand model relies upon the existence of extensive base year traffic count data. Volume-to-count ratios generated by the model are used to measure the ability of a travel demand highway assignment model to simulate known traffic conditions. Traffic counts are needed for a variety of different roadway categories distributed throughout the study area in order to validate highway assignment performance among screenlines, facility types, area types, and lane configurations. As part of the 2007 model update and Congestion Management Plan Update, the TPO identified locations along CMP routes and in the 2007 model where additional counts were needed. The TPO collected these supplemental counts in 2008 to assist with validation. As a result, year 2007 traffic counts available from TDOT, GDOT, Hamilton County, and the City of Chattanooga were included in the 2007 traffic count field used to calculate validation statistics. However, a year 2008 traffic count field was added to the model network to include these supplemental traffic counts collected in 2008. Since the base year of the model was 2007, these 2008 counts were not included in the validation statistics. However, they were used to supplement validation efforts and compare to 2007 traffic counts for accuracy.
2.5 Screenline Locations Screenlines are drawn across the model network throughout various parts of the study area to summarize traffic volumes in subareas and along major corridors. These screenlines are used to report an aggregate volume-to-count ratio for all of the links that comprise any given screenline. This allows for measurement of travel flows between subareas of the study area. Screenlines typically follow natural features, major transportation facilities, or political boundaries. Also, screenlines can be used to cordon off certain portions of the study area in order to measure the flows into and out of those areas (such as measuring the flow of travel demand into and out of central business districts (CBDs) or the external model boundary). As part of the previous 2030 LRTP update, 10 screenlines were identified and added to the TransCAD model network. These screenlines were checked to ensure that their orientation coincided with traffic count locations. Included in these 10 screenlines is an external cordon line that measures behavior of the external model. Also included is a partial cordon line around downtown Chattanooga and a variety of cut lines to allow for more detail in observing trip flow behaviors. The model network includes a field to indicate screenline codes one through 10, which are illustrated in Figure 2.19.
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Figure 2.18 Screenline Locations
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Chattanooga TPO 2035 LRTP – Volume 3: Travel Demand Model Documentation and User’s Guide
2.6 Travel Surveys Household Travel Diary Survey In 2002, a household travel diary survey was conducted to determine trip generation rates, average trip lengths, auto occupancy factors, and other characteristics used in model development and validation. The same rates and parameters derived from the 2002 household travel diary survey for the last model update were used for the 2007 model update as part of this 2035 LRTP. Typically, household travel diary surveys are conducted every 10 years to accurately reflect travel characteristics of the region. Pending funding availability, the TPO intends to conduct a new household travel diary survey in calendar year 2011. The results of the 2011 travel diary survey will be incorporated into the new 2010 base year model for the next LRTP update.
External Origin and Destination Survey In 2002, a roadside origin-destination intercept survey designed to obtain characteristics of travelers entering, exiting, and passing through the region from locations outside the CHCNGA study area was conducted. During the last 2030 LRTP Update, it was determined that the results from the 2002 external origin and destination survey were biased. It was determined that the percentage of through trips were not reliable as the interstate surveys were conducted on ramps at interchanges and rest areas. Vehicles were not pulled off to the side of the road on the mainline interstate segments where most External-External (EE) trips occur. The vehicles that were surveyed already were stopping at the interchange or rest area. Therefore, the results provide a significant bias towards Internal-External (IE) trips and EE trips were thus underestimated. The percent IE/EE splits from the origin and destination survey were subsequently compared to the old 2000 MINUTP model and it was determined that the old 2000 MINUTP model percent splits appeared more reasonable. The MINUTP splits were used as a starting point for the previous 2000 model validation conducted in 2005 and were later modified during the 2000 model validation process. As a result, the 2002 roadside origin-destination intercept survey was not used within the TransCAD model for this current 2035 LRTP Update,. With the exception of new external stations, the updated model as part of this 2035 LRTP Update used the same IE/EE splits from the last model. Any new external stations, which are minor roads with low traffic counts, assumed 100 percent IE trips. However, the TPO intends to conduct a new external origin and destination survey during the fall of 2010. In the meantime, the TPO will be designing the sampling plan and survey instrument. The results of the 2010 external origin and destination survey will be used to validate the external model for the 2010 base year validation as part of the next LRTP update.
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3.0 External Trips 3.1 External Model Initial development of an external model requires that external trips be divided into at least two categories: internal to external (IE) trips and external to external (EE) trips. IE trips are those trips that either have an origin outside of the study area and a destination within the study area or vice versa. EE trips have both an origin and a destination outside of the study area, but pass through the study area. EE trips are preloaded in the CHCNGA model, as it is not usually expected that EE trips will reroute due to congestion. This is because EE trips generally consist of long-distance travelers not familiar with the local street system. There are two input files that describe external trips in the model. These are the TAZ geography file and the EE trips matrix file. Although the TAZ geography input file is part of the trip generation process, it is integral to generating the IE trips for the external model. As noted in Section 2.6, the percent IE/EE splits for each external zone were initially derived from the old MINUTP 2000 external model and refined during the last model update. The percent IE trips were applied to the 2007 AADT to calculate the total number of IE trips at each external zone for the TAZ geography file. The EE trips input matrix file (year_EXTERNAL-EXTERNAL.mtx) is generally the residual left after estimating IE trips in the TAZ geography file (TAZ_2007.dbd). The percentage of EE trips was applied to the AADT per external zone and then distributed from each origin zone to each destination zone using distribution patterns from the 2000 model EE trips file. Eight new external stations were added to the 2007 model above and beyond the 30 external stations included in the previous 2000 model. Year 2007 traffic counts at each of the 38 external stations were utilized to determine the total external trips. The same percent distribution of external-external (EE), or through trips, versus internal-external (IE) trips at each of the original 30 external zones used in the 2000 model was used for the 2007 model. Since the eight new external stations in the 2007 model were located along minor facilities, it was assumed that 100 percent of the external trips were attributed to IE trips, or those with one trip end inside the TPO region and one trip end outside the TPO region. It should be noted that traffic counts for the external stations were coded in to the adjacent link to the external centroid connector in the model network so that the correct area type, facility type, and number of lanes is associated with the link. Table 3.1 below demonstrates the percentage of IE and EE trips at each of the 38 external stations in the 2007 model.
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Table 3.1
Internal-External (IE) and External-External (EE) Percentage Splits Percent Split
Zone 2007
36
Description
IE
EE
800
(I-75 S)
67%
33%
801
(US-41 Chattanooga Road)
69%
31%
802
Old Ringgold Road
98%
2%
803
(GA SR 151 Alabama Highway)
81%
19%
804
GA SR 95
100%
0%
805
Ringgold Road
65%
35%
806
(GA SR 1, U.S. 27 S)
58%
42%
807
Straight Gut Rd.
100%
0%
808
(GA SR 341 Cove Road)
93%
7%
809
GA SR 193
92%
8%
810
Lula Lake Road
91%
9%
811
(GA SR 157/ 189 Lookout Mountain Scenic Highway)
97%
3%
812
(GA SR 58 , U.S. 11, Birmingham Pike)
75%
25%
813
I-59
82%
18%
814
I-24
64%
36%
815
TN SR 134
98%
2%
816
U.S. 64, U.S. 72, U.S. 41, TN SR 2
63%
37%
817
TN SR 27 Suck Creek Road
98%
2%
818
(TN SR 8, U.S. 127 Taft Highway)
58%
42%
820
(U.S. 111)
62%
38%
821
Retro Hughes Road
2%
98%
822
(TN SR 309 Leggett Road)
12%
88%
823
(TN SR 29, U.S. 27 N, Rhea Co. Highway)
31%
69%
825
TN SR 58
72%
28%
826
Old State Highway 58
66%
34%
827
TN SR 60 Georgetown Road
23%
77%
828
TN SR 312 Harrison Pike
100%
0%
829
(I-75 N)
71%
29%
830
(U.S. 11, U.S. 64, SR 2 S. Lee Highway)
94%
6%
831
McDonald Road
100%
0%
832
Old Alabama Road SW
100%
0%
833
Candies Creek Road SW
100%
0%
834
Tunnel Hill Road
100%
0%
835
TN SR 317 Weatherly Switch Trail SW
95%
5%
836
Bill Stewart Road
98%
2%
837
TN SR 2 Varnell Road
94%
6%
Chattanooga TPO 2035 LRTP – Volume 3: Travel Demand Model Documentation and User’s Guide
Figure 3.1 External Station Locations
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3.2 External Validation Adjustments Validation adjustments to the external model consisted of modifying the TAZ geography and EE trips files. Several iterations of the external model were executed in order to balance volumes at the external stations in such a manner so the addition of IE and EE trips matched the total AADT of each external station. Special generator attractions were added to some of the external stations in an attempt to correct overassignments that were occurring in their vicinity. In the south of the model, there was major overassignment on several north-south arteries and the thought was that some of the trips trying to go north into Chattanooga should really be headed towards Dalton and areas to the South. To correct that, attractions were added to some of the external stations, such as I-75 South, to pull the trips in that direction. Similarly, the roads coming off the Cumberland Escarpment (Walden Ridge) into the Tennessee River Valley and I-75 and SR 60 leading into the Cleveland, Tennessee area received the same treatment with attractors being placed to pull some trips in that direction, rather than going into Chattanooga.
3.3 External Validation Results Model validation results are described later in Section 7.0 on the highway assignment. In particular, a review of the external cordon line and other screenlines close to the model boundary indicate a reasonable match of external travel movements. The external cordon line achieves a volume-over-count ratio of 1.00.
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4.0 Trip Generation Just as with the previous 2000 model, the CHCNGA 2007 model uses a cross-classification trip generation process for trip productions along with trip rate equations for trip attractions. Trip productions and attractions are generated by zone using trip production rates derived from the Chattanooga household travel survey and trip attraction rates borrowed from the Knoxville household travel survey. This section discusses the Trip Generation model step.
4.1 Trip Generation Process During the previous 2030 LRTP Update adopted in 2005, the 2002 Chattanooga Household Travel Survey data was evaluated to determine what variables impact travel patterns the most in the Chattanoga region. As a result, a cross-classification method based on auto availability and children per household was implemented. This same method was used during this 2035 LRTP update. Other potential explanatory variables from the survey, such as household size and income, were evaluated. However, trip rate matrices derived from these variables showed inconsistent patterns. Therefore, both the CHCNGA 2000 and 2007 models used trip rates developed for the four following auto availability categories: •
Zero autos per household;
•
One auto per household;
•
Two autos per household; and
•
Three or more autos per household.
Trip rates for the four auto availability categories are cross-classified by categories, as follows: •
Zero children per household;
•
One child per household; and
•
Two or more children per household.
Auto availability and children per household data were derived from the 2000 Census. Trip production rates were developed for the following trip purposes: •
Home-Based Work (HBW);
•
Home-Based School (HBSchool);
•
Home-Based Shop (HBShop);
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Chattanooga TPO 2035 LRTP – Volume 3: Travel Demand Model Documentation and User’s Guide
•
Home-Based Social/Recreation (HBSR);
•
Home-Based Other (HBO); and
•
Nonhome Based (NHB).
Trip production rates by purpose are provided in Table 4.1. Trip production rates for hotelmotel units are provided in Table 4.2. Trip attraction rates for HBW, HBSchool, HBShop, HBSR, HBO, and NHB purposes were borrowed from the Knoxville model as these rates were more appropriate for use in Chattanooga than the Northeast Florida Regional Planning Model trip attraction rates used in the previous 2000 model. New trip attraction rates for the CHCNGA model specific to Chattanooga would have required an employer survey in addition to the household travel survey. Trip attraction rates for the light-duty truck, medium-duty truck, and heavy-duty truck trip purposes were derived from the FHWA Quick Response Freight Manual and did not change since the last 2000 model. Trip attraction rates are depicted in Table 4.3. Further detail on adjustments made to trip rates are included in the following section. The productions and attractions output from the trip generation process are stored by zone by trip purpose in the TAZ geography file (TAZ_2007.dbd). This same master file includes the socioeconomic data for each model year. As a result, the number or density of productions and attractions can be illustrated by TAZ within TransCAD or a GIS.
4.2 Trip Generation Validation Adjustments Adjustments were made to the trip attraction rates and special generators in order to validate the trip generation step in the travel demand model. Further detail is provided below.
Trip Attraction Rates As noted above, trip production rates utilized in the 2007 model are the same as those utilized in the 2000 model. However, trip attraction rates were modified in the 2007 model as they were borrowed from the Jacksonville, Florida region for the previous 2000 model. Trip attractions for some purposes, such as HBW, differed appreciably from the trip productions and it was therefore decided to borrow trip attraction rates from the Knoxville model and adjust where appropriate in an attempt to achieve closer matches. Utilizing Knoxville trip attraction rates is likely more appropriate for the Chattanooga region due to potential differences in travel characteristics in the Jacksonville, Florida region. The Knoxville trip attraction rates documented in the Knoxville Regional Travel Demand Model Validation Report of March 2004 were based on their household travel survey using regression analysis. Using the Knoxville attraction rates resulted in some improvement in the unbalanced ratios for most trip purposes in Chattanooga. Adjustments were necessary to some of the trip attraction rates as trip purposes did not correlate perfectly between the
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Knoxville and Chattanooga models. The final Chattanooga 2007 model trip production and attraction rates are listed below.
Total Employment
Agricultural/Mining/ Construction
Manufacturing/ Transportation
Retail
Service
Government
School Enrollment
Total Population
New Chattanooga Trip Production and Attraction Rates
Total Households
Table 4.1
Home-Based Work
0.00
0.51
0.00
0.00
0.00
0.00
0.00
0.00
0.00
Home-Based School
0.00
0.00
0.00
0.00
0.00
0.00
0.00
1.72
0.00
Home-Based Shop
0.00
0.00
0.00
0.00
0.78
0.11
0.19
0.00
0.20
Home-Based Social Recreation
0.00
0.00
0.00
0.00
0.48
0.06
0.12
0.00
0.12
Home-Based Other
0.00
0.00
0.00
0.00
1.38
0.19
0.35
0.00
0.36
Nonhome-Based
1.54
0.36
0.00
0.00
3.83
0.31
0.64
0.00
0.00
Light-Truck
0.10
0.00
0.30
0.25
0.25
0.15
0.15
0.00
0.00
Medium-Truck
0.05
0.00
0.10
0.10
0.10
0.05
0.05
0.00
0.00
Heavy-Truck
0.05
0.00
0.05
0.05
0.05
0.05
0.05
0.00
0.00
Special Generators The addition of special generators is a subjective and iterative process. Ideally, a model should only have special generators where standard trip rate equations would not calculate any trips (e.g., recreational areas and group quarters). However, most models also need special generators to account for locations where trips are significantly under- or overestimated due to the unique nature of the land use (airports, colleges, universities, and tourist attractions typically fall into this category). Volume-to-count ratios in the areas surrounding each of these potential special generators were reviewed to determine whether or not special generators were needed. Special generator trips are derived by manually calculating trips using special generator trip rates and substituting the manual results for the machine-generated results.
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Chattanooga TPO 2035 LRTP – Volume 3: Travel Demand Model Documentation and User’s Guide
Although the 2000 TransCAD model included special generators at the airport, the University of Tennessee at Chattanooga, Chattanooga State College, and Chester Frost National Park, no special generators were assumed at the beginning of 2007 model validation effort. During the validation process, several of the special generators included in the 2000 model were added back in to the 2007 model, as well as several new special generators. A complete listing of special generators used in the model is provided in Table 4.2.
Table 4.2
Special Generator Locations
Zone 17a
Description UTC Dorms
18
UTC Dorms
19
UTC Dorms
48*
UTC Dorms
49
UTC Dorms and students
50
UTC Dorms and students
135 157
Lovell Field (CHA) Chattanooga Metro Airport a
190
Newly added – Hamilton Place Mall Chattanooga State College
197
Chester Frost Park
800
a
I-75 South External Station
801
a
U.S. 41/Chattanooga Road External Station
805
a
Ringgold Road External Station
806a
GA SR 1/U.S. 27 South External Station
818
a
TN SR 8/U.S. 127/Taft Highway External Station
820
a
U.S. 111 External Station
822
a
TN SR 309/Leggett Road External Station
823
a
TN SR 29/U.S. 27/N. Rhea Co. Hwy. External Station
827
a
TN SR 60/Georgetown Road External Station
829
a
I-75 North External Station
a
Indicates new special generator added to 2007 model.
As noted in Section 3.2, special generator attractions were added to some of the external stations in an attempt to correct overassignments that were occurring in their vicinity. In the south of the model, there was major overassignment on several north-south arteries and the thought was that some of the trips traveling north into Chattanooga should really be traveling towards Dalton and areas to the South. To correct that, attractions were added to
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Chattanooga TPO 2035 LRTP – Volume 3: Travel Demand Model Documentation and User’s Guide
some of the external stations, such as I-75 South, to attract trips in that direction. Similarly, the roads coming off the Cumberland Escarpment (Walden Ridge) into the Tennessee River Valley and I-75 and SR 60 leading into the Cleveland, Tennessee area received the same treatment with attractors being placed to pull some trips in that direction, rather than going into Chattanooga. Special generators are contained in the special generator input file in the format of number of productions or attractions by trip purpose by TAZ. The special generators input file is specific to each year and is titled, year_SPGEN.bin.
4.3 Trip Generation Validation Results Table 4.3 provides comparisons of aggregate trips per household, person, and employee, along with persons per household between the CHCNGA 2007 TransCAD model and the previous 2000 model. There were approximately nine person trips per household in the Chattanooga region in the 2007 model, within TDOT’s target range of 8.5 to 10.5.
Table 4.3
Aggregate Trip Rates Chattanooga
Standards
Unit of Measure
2007
2000
TDOT
FHWA
Persons per Household
2.38
2.50
n/a
n/a
Internal Trips per Household
9.00
9.44
8.5-10.5
8.0-14.0
Internal Trips per Person
3.78
3.78
n/a
3.5-4.0
HBW Trips per Employee
1.12
0.74
n/a
n/a
Employees per Person
0.51
0.73
n/a
n/a
Total Population
425,666
395,061
Total Households
178,905
158,055
Total Employment
218,612
287,918
Table 4.4 demonstrates the average number of trips per household by trip purpose in the 2007 model.
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Chattanooga TPO 2035 LRTP – Volume 3: Travel Demand Model Documentation and User’s Guide
Table 4.4
2007 Trips per Household by Trip Purpose
Trip Purpose
2007 Trips Per Household
Home-Based Work
1.37
Home-Based School
0.55
Home-Based Shop
1.05
Home-Based Socrec.
0.64
Home-Based Other
1.87
Non Home-Based
2.75
As indicated in Table 4.5 below, HBW trips represent approximately 16.6 percent of all the trips generated in the Chattanooga region, slightly below TDOT’s target of 18 percent (excludes commercial vehicle and external trips). Approximately 50 percent of trips in the Chattanooga region can be attributed to HBSchool, HBShopping, HBSR, and HBO trips purposes, within TDOT’s target of 47 to 54 percent. NHB trips are slightly higher than the desired range of 22 to 31 percent at 33 percent. Commercial vehicles represent approximately seven percent of the trips in the 2007 model, a reduction compared to the 2000 model. It must be noted, however, that employment in the 2007 model is lower than for the 2000 model, contributing to the reduced commercial vehicles, as demonstrated in technical submittal #2. It should be noted that part of this low-simulation problem is a function of the household travel survey which has shown somewhat surprising results based on previous trip rate analyses of the survey data. The TPO intends to conduct a new household survey when the budget is available so that a new cross classification matrix of trip rates might be calculated.
Table 4.5
Percent of Trips by Purpose Percent Trips
Trip Purpose
46
2007
Home-Based Work
17%
Home-Based School
7%
Home-Based Shop
13%
Home-Based Socrec.
8%
Home-Based Other
23%
Non Home-Based Total
TDOT Target 17%
18-27%
50%
47-54%
33%
33%
21-31%
100%
100%
100%
Chattanooga TPO 2035 LRTP – Volume 3: Travel Demand Model Documentation and User’s Guide
5.0 Trip Distribution Trip Distribution models link trip productions and attractions between pairs of TAZs. These interchanges are typically calculated through application of a Gravity Model. Gravity Models distribute trips among zones directly proportional to the relative attractiveness of each individual zone and inversely proportional to the friction between zones (i.e., distance). The result is a matrix of person trips that is later balanced in order to be defined in terms of origins and destinations (as opposed to productions and attractions). Resulting person trip matrices are processed later in the model chain during mode choice to convert these to balanced vehicle trips.
5.1 Trip Distribution Model Structure The trip distribution step of the model estimates or predicts the spatial pattern of trips between origin and destination zone pairs. The general distribution process includes the building of highway networks and travel-time skims as well as application of the Gravity Model. This includes updating the travel-time skims with intrazonal and terminal times, distributing trips between zones using a Gravity Model, and producing a set of congested highway skims. The primary input data used for trip distribution is the friction factor (F_FACTORS.bin) file. This file is used by the Gravity Model to measure the effects of spatial separation between zones for the purpose of trip distribution. It is generally assumed that trips are less likely to be allocated to destinations with greater travel times if alternative destinations with lesser travel times and similar attractiveness are available. Friction factors from the previous CHCNGA 2000 model were used as a starting point for the new CHCNGA 2007 TransCAD model. They were further modified during the model validation process as discussed in Section 5.2. Intrazonal times represent the travel time within or across a zone. These times are calculated as one-half the travel time from one zone to the nearest adjacent zone. Terminal times represent the time involved at either end of a trip to travel from an origin to a vehicle or from the vehicle to a final destination. More specifically, this accounts for the time necessary to walk to or from the vehicle used for any given trip. Table 5.1 lists the terminal times by area type used in the CHCNGA 2007 TransCAD model. Terminal times inside the study area are typically greatest in central business districts.
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Chattanooga TPO 2035 LRTP – Volume 3: Travel Demand Model Documentation and User’s Guide
Table 5.1
Terminal Times
Terminal Times
Area Types
Area Type Descriptions
5
1
Central Business District (CBD)
3
2
Central Business District (CBD) Fringe
1
3
Residential
2
4
Outlying Business District
1
5
Rural
1
6
Urban Undeveloped
1
7
Mountainous
2
8
Industrial
10
9
External Centroid Connector
5.2 Trip Distribution Model Development and Validation Validation of the CHCNGA 2007 trip distribution model primarily involved modification of the highway network, friction factors, and K-factors. Evaluation of the trip distribution model was accomplished by comparing statistics for average trip length and the percentage of intrazonal trips between the CHCNGA 2007 model and other comparable models in the southeast, including the previous CHCNGA 2000 model.
Network Link Attributes As part of the model validation process, the TPO conducted an in depth review of the highway network, particularly in downtown Chattanooga and in the Enterprise South Industrial Park. Network characteristics were updated to more accurately reflect the conditions of the roadway system in the CHCNGA study area for the year 2007. In addition to updating existing roadway characteristics, the TPO added a new area type (8-Industrial). Field review also resulted in some changes to network characteristics. The master network, which includes all network years, is titled LRTP_MASTER_NETWORK.dbd.
Friction Factors Initially, friction factors from the previous 2000 model, which were borrowed from the earlier MINUTP model, were used as part of the validation of the 2007 model. However, upon review of the average trip lengths, it was determined that adjustments to the friction factors were necessary. As a result, the TPO first developed and calibrated new friction factors to match the Chattanooga 2002 Household Travel Diary Survey data. However,
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these new friction factors resulted in unsatisfactory results. Average trip lengths were proving to be shorter than expected and overall validation results were consequently worse. As a result, the original friction factors from the previous 2000 model were iteratively adjusted to achieve better trip length distribution characteristics. Several iterative runs were performed to arrive at the final friction factors used for the remainder of the model validation runs. The final friction factors (F_FACTORS.bin) are included in the complete model dataset that is being provided to TDOT and GDOT as part of this submittal.
K-Factors K-Factors are sometimes used during the validation process to adjust the trip patterns estimated or predicted by the Gravity Model. K-Factors are typically used at water crossings and between areas with different socioeconomic characteristics, (e.g., rural verses urban conditions). Just as was included in the previous 2000 model, K-factors were necessary between areas north and west of the Tennessee River and areas south and east of the Tennessee River, as well as between Georgia and Tennessee. However, unlike the previous model, the K-factors were not directionally skewed to/from Georgia and Tennessee. K-Factors are stored in a zone-to-zone matrix file (K_FACTORS.mtx) in TransCAD. Tables 5.2 and 5.3 demonstrate the number of trips between K-Factor districts for the years 2007 and 2035, respectively.
Table 5.2
2007 Trips Between K-Factor Districts 2007 K-Factor District Trip Interchanges
North of River
South of River in Tennessee
Georgia
External Stations
North of River
295,216
48,598
13,033
54,204
South of River in Tennessee
124,147
717,149
115,740
110,646
Georgia
13,969
59,732
187,369
40,186
External Stations
12,768
12,938
9,754
34,391
District
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Chattanooga TPO 2035 LRTP – Volume 3: Travel Demand Model Documentation and User’s Guide
Table 5.3
2035 Trips Between K-Factor Districts 2035 K-Factor District Trip Interchanges
District
North of River
South of River in Tennessee
Georgia
External Stations
North of River
412,044
79,091
19,644
77,977
South of River in Tennessee
167,164
1,045,880
156,318
163,274
Georgia
16,718
75,241
252,564
55,793
External Stations
18,603
20,753
13,464
48,564
Penalties and Prohibitors A turn penalty and/or prohibitor file allows for the adjustment of travel times on specific links by either inducing a time penalty to pass from one link to another or prohibiting the movement all together. Prohibitors are typically confined to ramp intersections. However, since interstates and expressways are dual-line coded in the model network, the need for turn prohibitors at interchanges is eliminated. As a result, no prohibitors were included in the CHCNGA 2007 TransCAD model. Furthermore, K-factor and speed adjustments provided satisfactory distribution results without requiring travel-time penalties. However, it was found necessary to add penalties, primarily along the Tennessee River bridges, to correct local imbalances. Table 5.4 below lists the locations and amount of the penalties. In addition, there is a penalty along Mountain Creek Road, as this corridor is a
winding, narrow roadway with a steep grade. Other characteristics coded into the network fail to fully address the hazards of taking this route, which was dramatically overassigning. Penalties are stored in a binary file titled CHATT_TURN_PENALTY.bin.
Table 5.4
Penalties
Roadway
50
Penalty (minutes)
U.S. 27 Bridge
1.35
N. Market Street Bridge
1.10
Dupont Parkway
0.25
Mountain Creek Road
2.00
Chattanooga TPO 2035 LRTP – Volume 3: Travel Demand Model Documentation and User’s Guide
5.3 Trip Distribution Model Results The two fundamental Gravity Model checks discussed in this section are the average trip length by purpose and the percentage of intrazonal trips. An analysis of volume-to-count summaries along screenlines also can be helpful in establishing the accuracy of trip distribution. However, as screenline summaries apply more significantly to the analysis of traffic assignment, these will be discussed later in Section 7.0.
Average Trip Length by Purpose Table 5.5 demonstrates the final average trip lengths for each trip purpose in comparison to the old 2000 model. In addition, year 2007 HBW trip lengths were compared to those included in the Census Transportation Planning Package (CTPP) for the year 2000 in Hamilton, Catoosa, and Walker Counties. HBW trip lengths improved in the 2007 model compared to the 2000 model as they are closer to the CTPP trip lengths. However, the 2007 model HBW trip lengths are still slightly shorter when compared to the CTPP trip lengths. This is as a result of the daily nature of the model compared to the highly peak hourweighted CTPP figure. The modest expansion of the model to include all of Catoosa County since the last LRTP partially explains the reduction in Internal-External trip times. All of the 2007 trip lengths are within acceptable limits provided by the Federal Highway Administration (FHWA). No trip length targets have been established by TDOT at this time.
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Table 5.5
Average Trip Length (in Minutes) 2007
2000
Chattanooga (TransCAD)
Chattanooga (TransCAD)
CTPP (Hamilton)
CTPP (Catoosa)
CTPP (Walker)
FHWA Target
Home-Based Work
18.26
16.36
21.20
23.70
26.50
11.2-35.4
Home-Based School
13.85
14.48
n/a
n/a
n/a
8.9-15.9
Home-Based Shop
12.84
13.78
n/a
n/a
n/a
8.6-18.7
Home-Based Social Recreation
13.55
11.38
n/a
n/a
n/a
10.4-17.3
Home-Based Other
12.44
14.41
n/a
n/a
n/a
Nonhome-Based
14.18
15.44
n/a
n/a
n/a
8.1-17.1
Commercial Vehicles
17.88
19.64
n/a
n/a
n/a
n/a
Light-Truck
17.78
18.79
Medium-Truck
17.20
17.95
Heavy-Truck
20.75
22.17
Internal-External
37.38
41.04
n/a
n/a
n/a
n/a
Total
14.53
18.68
n/a
n/a
n/a
n/a
Purpose
Intrazonal Trip Distribution The 2007 model validation effort involved significant splitting of zones, particularly towards the periphery. This reduced the average size of zones. Consequently, as indicated in Table 5.6, the percent intrazonal trips fell slightly to below nine percent as compared to above nine percent for the 2000 model. As expected, given the tendency of individuals to travel further for work purposes, the percent intrazonal trips for HBW are lower than for other purposes at just under two percent. Providing the percent of intrazonal trips by purpose assists with assessing zone size and the attenuation of trips.
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Table 5.6
Intrazonal Trips by Trip Purpose Chattanooga (TransCAD) Percent Intrazonal
Purpose
2007
2000
Home-Based Work
1.93%
7.04%
Home-Based School
6.63%
11.12%
Home-Based Shop
12.51%
9.93%
Home-Based Social Recreation
11.98%
21.08%
Home-Based Other
12.96%
11.16%
Nonhome-Based
9.61%
8.02%
Commercial Vehicles
2.77%
3.06%
Light-Truck
2.74%
2.95%
Medium-Truck
3.46%
4.15%
Heavy-Truck
1.27%
1.19%
8.89%
9.18%
Total
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6.0 Mode Choice Currently, the Chattanooga TransCAD model does not include a transit network/ pathbuilding component. At the beginning of the 2035 LRTP Update, the TPO intended to add transit to the TransCAD model contingent upon the availability of existing data to validate the new transit component. However, upon review of the data, it was determined that an on-board transit survey was needed in order to validate a new transit model. The TPO will be developing the survey instrument for the on-board transit survey shortly after the adoption of the 2035 LRTP Update. Subsequently, the TPO will conduct the on-board survey in the fall of 2010, in preparation for the next base year 2010 model for the LRTP Update to be adopted in 2014. The TPO intends to add the transit network/pathbuilding component to the next generation of the TransCAD model in time for the next LRTP update. In the interim, the same auto occupancy model used in the model from the previous 2030 LRTP Update is being used for the current 2035 LRTP Update. Ratios of persons per vehicle were derived from the local household diary survey conducted in the Chattanooga region in 2002. These persons per vehicle ratios by trip purpose were used to convert person trips to vehicle trips. Although the current model does not include a transit network, it does include a vehicle occupancy allocation component that disaggregates vehicle trips by single occupancy vehicle (SOV) and high-occupancy vehicle (HOV) categories. Trips also are allocated by truck categories. This is useful in evaluating HOV lanes or truck-exclusive lanes. This section of the report describes the different mode choice structures used to generate the three types of trip tables for input into their respective assignment processes, as follows: •
General Highway Assignment;
•
Exclusive HOV or Truck Lane Assignment; and
•
Time-of-Day Assignment.
Each of the three mode choice processes are detailed below.
6.1 Mode Choice Model Structure for General Highway Assignment The CHCNGA 2007 model was validated using the General Highway Assignment process. The CHCNGA 2007 mode choice model first balances the External-External (EE) trip table and then adds these preloaded EE trips to the trip table, including all of the other trip purposes. The six internal passenger vehicle trip purposes (HBW, HBSchool, HBShop, HBSR, HBO, and NHB) are then converted from person trips to vehicle trips using the auto occupancy rates included in Table 6.1. Auto occupancy rates were calculated by purpose
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Chattanooga TPO 2035 LRTP – Volume 3: Travel Demand Model Documentation and User’s Guide
from the household travel characteristics survey. The three truck purposes (LDTK, MDTK, and HDTK) and the Internal-External (IE) trip purpose already are in vehicle trips and are therefore not converted during mode choice.
Table 6.1
Auto Occupancy Rates
Purpose
Persons/Auto
Home-Based Work
1.12
Home-Based School
1.12
Home-Based Shop
1.48
Home-Based Social/Recreational
1.72
Home-Based Other
1.65
Nonhome-Based
1.68
Auto occupancy rates are only applied when running the General Highway Assignment option. This model option was used to produce the validation summary statistics found in Section 7.0 of this report.
6.2 Mode Choice Model Structure for Exclusive HOV or Truck Lanes As noted earlier, a vehicle occupancy allocation component is included in the mode choice model in order to evaluate the impact of exclusive HOV or truck lanes. This component disaggregates vehicle trips into the following three categories: •
SOVs;
•
HOVs with two persons per vehicle; and
•
HOVs with three or more persons per vehicle.
The share of SOV and HOV trips were generated from the Chattanooga household travel diary survey and are provided by trip purpose in Table 6.2 below. An iterative process was used to adjust the factors during the last model update, as the initial run using the factors directly from the survey were significantly overestimating the number of trips in the model. As a result, the factors were adjusted proportionately to achieve the correct number of trips. The same factors used in the final 2000 model were used in the current 2007 model.
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Table 6.2
Vehicle Occupancy Allocation by Trip Purpose Trip Purpose
Vehicle Occupancy
HBW
HBSchool
HBShop
HBSR
HBO
NHB
SOV
80.5%
80.0%
41.0%
25.0%
28.7%
26.6%
HOV 2
14.6%
15.0%
44.3%
56.3%
53.5%
46.4%
HOV 3+
4.9%
5.0%
14.8%
18.8%
17.8%
27.0%
100.0%
100.0%
100.0%
100.0%
100.0%
100.0%
Total
Based on the Chattanooga external origin/destination survey, approximately 39 percent of external trips were allocated to SOV trips, 24 percent to HOV2 (two persons/vehicle) trips, and 23 percent to HOV3 (three or more persons/vehicle) trips. The remaining 14 percent of external trips were allocated to truck purposes. Trips also are allocated by truck categories, as described earlier in this report. These trips already are in vehicle trip equivalents so vehicle occupancy conversions are not needed: •
Light-Duty Truck;
•
Medium-Duty Truck; and
•
Heavy-Duty Truck.
Based on the Chattanooga external origin/destination survey, approximately five percent of external trips were allocated to light-duty truck trips, five percent to medium-duty truck trips, and four percent to heavy-duty truck trips. The share of truck and SOV/HOV trips are only applied when running the HOV Only or Truck Only Assignment processes.
6.3 Mode Choice Model Structure for Time-of-Day Model Once all trip purposes are converted to vehicle trips, a.m. and p.m. peak hour trip tables can be generated using the peak hour factors derived from the household travel diary survey. As part of the evaluation of the household travel survey, the percent of trips that occur within each hour of the day (peak hour factors) were calculated and are depicted in Table 6.3. The a.m. peak hour occurs between 8:00 a.m. and 9:00 a.m., as the highest percent of trips in the morning occurs during that hour in Chattanooga, at approximately 7.4 percent. The p.m. peak hour occurs between 5:00 p.m. and 6:00 p.m., as the highest percent of trips in the afternoon occurs during that hour, at approximately 8.7 percent.
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The time-of-day model is an optional step that can only be applied to the General Highway Assignment model and is done by checking the a.m. Assignment and/or p.m. Assignment boxes in the user interface before running the General Highway Assignment. It should be noted that the time-of-day factors are applied after the trips are assigned and thus, do not account for diversion in trips as a result of peak hour congestion. Therefore, it is not a true time-of-day component. The TPO is exploring the possibility of developing a true time-of-day model for the Chattanooga region that will be validated based on traffic counts by time-of-day. Since time-of-day models are necessary for transit modeling, it will likely be a combined model enhancement effort.
Table 6.3
Temporal Distribution of Trips
Hour 12:00 to 1:00 a.m.
0.4%
1:00 to 2:00 a.m.
0.1%
2:00 to 3:00 a.m.
0.2%
3:00 to 4:00 a.m.
0.0%
4:00 to 5:00 a.m.
0.1%
5:00 to 6:00 a.m.
0.5%
6:00 to 7:00 a.m.
2.3%
7:00 to 8:00 a.m.
7.0%
8:00 to 9:00 a.m.
7.4%
9:00 to 10:00 a.m.
4.7%
10:00 to 11:00 a.m.
5.3%
11:00 a.m. to 12:00 p.m.
6.1%
12:00 to 1:00 p.m.
6.9%
1:00 to 2:00 p.m.
6.8%
2:00 to 3:00 p.m.
6.6%
3:00 to 4:00 p.m.
8.0%
4:00 to 5:00 p.m.
7.5%
5:00 to 6:00 p.m.
8.7%
6:00 to 7:00 p.m.
8.1%
7:00 to 8:00 p.m.
5.3%
8:00 to 9:00 p.m.
3.5%
9:00 to 10:00 p.m.
2.6%
10:00 to 11:00 p.m.
1.3%
11:00 p.m. to 12:00 a.m.
0.5%
Total Note: Percent of trips based on trips ending during time period.
58
Percent of Trips
100.0%
Chattanooga TPO 2035 LRTP – Volume 3: Travel Demand Model Documentation and User’s Guide
7.0 Highway Assignment The purpose of highway assignment models is to load vehicle trips onto the highway network. This results in traffic estimates on individual links that ultimately attempt to simulate general vehicular travel throughout the study area. Supplemental assignment processes were generated for simulating HOV and truck exclusive facilities, and time-of-day simulations. Validation of the highway assignment involved iterative modifications to centroid locations, verification of counts, and adjustment of speeds, capacities, K-Factors and other parameters related to trip distribution. A number of key evaluation statistics are generated during the assignment phase of the model. Volume-to-count ratios are compared by area type, facility type, laneage, and screenlines. Along with these statistics, the root mean squared error (RMSE) was generated by volume group. This section describes validation of the highway assignment model. It includes an overview of the model structure, development and adjustment of model parameters, and a review of model results.
7.1 Highway Assignment Model Structure Trips are loaded onto the network by means of an iterative equilibrium highway load program based on an all-or-nothing capacity restrained assignment. A total of 11 iterations are conducted during base year model execution (maximum iterations are set to 15) and the convergence parameter is set to 0.001. A series of statistical summaries are subsequently generated as a result of code added to the model script to report validation statistics. The supplemental exclusive lane assignment model is used to test scenarios where selected vehicle classes (e.g., single-occupant autos) are restricted from using selected lanes and ramps (e.g., HOV lanes). The time-of-day assignment model is used to obtain assignment volumes for specific time periods. These supplemental models are not normally executed when conducting a general traffic assignment where only total daily traffic volumes are desired.
7.2 Development and Validation of Highway Assignment Model In total, 23 major model runs were executed in order to validate the CHCNGA 2000 TransCAD model. In addition, several model runs were made inbetween major model runs to iterate minor adjustments. Model validation was accomplished by minimizing the difference between model simulated volumes and observed counts for the year 2007 on network links throughout the study area. As many count locations were accounted for as
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possible in order to ensure a wide range of coverage geographically as well as to incorporate as many examples of facilities and land uses located within the study area. Adjustments were made to key elements in the modeling process to achieve this validation. After each run, a summary of the results was compiled and analyzed in order to identify areas for improvement in the model and successful strategies toward validation. Appropriate changes consistent with the discoveries revealed during analysis were then implemented and subsequent runs were executed. This iterative process was continued until validation was achieved. Changes made to the model during highway assignment validation consisted mainly of iterative adjustments to speeds and highway network editing, including adjustment of centroids and centroid connectors. Other adjustments discussed elsewhere in this report also impacted highway assignment results.
7.3 Highway Assignment Validation Results In validating traffic assignment, final outcome of a travel demand model, common performance metrics include the following: •
Systemwide volume-to-count ratio;
•
Volume-to-count ratios by link group (area type, facility type, and number of lanes);
•
Volume-to-count ratios along screenlines;
•
Percent difference in model volumes and counts by volume group;
•
Systemwide coefficient of determination between assigned volumes and counts;
•
Systemwide percent root mean square error; and
•
Percent root mean square error by volume group.
Table 7.1 includes the volume-to-count ratios by facility type, area type, and number of lanes. Overall, the model is validating at 0.96, within acceptable limits. This also is an improvement in the overall validation since the 2000 model with a volume-to-count ratio of 0.95. Although the validation of expressways improved in the 2007 model, the validation of undivided principal arterials, minor arterials, and one-way facilities got worse when compared to the 2000 model. This can be attributed to the correction in the network coding in the 2007 model reflecting the 3rd and 4th Street one-way facilities in downtown Chattanooga. Furthermore, additional network detail was included in some portions of the model as a result of further TAZ splits, as well as a significant amount of more traffic counts being provided in the 2007 model. Therefore, although the 2007 model may indicate lower volume-to-count ratios for some facility type categories, it is likely more accurate than the 2000 model due to the additional traffic counts. In addition, no ramp counts were available in the 2000 model and have since been added to the 2007 model validating at a 2007 volume-
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to-count ratio of 0.99. Four of the six facility type categories that have targets set by TDOT are within acceptable limits. Although no targets have been established to date by TDOT for volume-to-count ratios by area type, seven of the eight area type categories are validating within +/- 10 percent. In addition, the new industrial area type category is validating at 0.90. The CBD area in downtown Chattanooga is validating at 0.74, which has historically validated lower than other categories in the Chattanooga model. With the exception of one-lane facilities (by direction), the 2007 model is validating better within each lane category compared to the old 2000 model.
Table 7.1
Volume Over Count Ratios by Facility Type, Area Type and Number of Lanes Chattanooga Volume/Count Ratio 2007
2000
TDOT Target
1. Interstate
1.02
0.98
+/- 7%
2. Expressway
1.04
0.94
+/- 7%
3. Principal Arterial Divided
0.98
0.98
+/- 10%
4. Principal Arterial Undivided
0.86
0.94
+/- 10%
5. Minor Arterial
0.80
0.88
+/- 15%
6. Collector
0.98
0.98
+/- 25%
7. Ramp
0.99
8. One-Way
0.49
0.71
1. CBD
0.69
0.88
2. CBD Fringe
0.97
0.92
a
Facility Type
n/a n/a
Area Type
3. Residential
0.92
0.96
4. OBD
0.95
0.92
5. Rural
1.07
1.10
6. Urban Undeveloped
1.04
1.02
7. Mountainous
1.09
0.95
8. Industrial
0.90
Number of Lanes by Direction 1
0.88
0.93
2
0.99
0.98
3
0.98
0.95
4
1.03
0.92
Total
0.96
0.95
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Chattanooga TPO 2035 LRTP – Volume 3: Travel Demand Model Documentation and User’s Guide
The 10 screenlines from the previous model were kept and utilized to assist in model validation for the 2007 model. Their positions capture all the major traffic flows in the Chattanooga Region and thus further adjustments and additions were deemed unnecessary. A map of the screenline locations was provided in Section 2.0 (Figure 2.18). Maps of volume-to-count ratios on each link in the model with a count are included in Appendix E. For eight of the 10 screenlines, the volume-to-count ratios fall within the +/- 10 percent target range of TDOT. Table 7.2 compares the volume-to-count ratio for each screenline in the 2007 model against the old 2000 model.
Table 7.2
Comparison of Volume-to-Count Ratios by Screenline Chattanooga Volume/Count Ratio
Screenline
2007
2000
1
1.00
0.97
2
1.01
0.94
3
0.88
0.97
4
0.99
0.91
5
0.82
0.90
6
0.93
0.99
7
1.10
1.09
8
0.91
1.06
9
1.06
1.02
10
1.00
1.00
Table 7.3 indicates the percent difference in model volumes and observed counts by volume group. All volume groups within the 2007 model achieve the established TDOT targets.
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Table 7.3
Percent Difference for Daily Volumes (Calculated for Links with Counts)
AADT
Chattanooga 2007TransCAD
TDOT Targeta
50,000
-5.90%
+/- 21%
The correlation coefficient of observed counts to model volumes (R2) is performing well at 0.95, exceeding TDOT’s target of 0.88, as demonstrated below in Figure 7.1.
Figure 7.1 Correlation of Assigned Versus Observed Volumes Assigned Volume 70,000 60,000 50,000 40,000 30,000 20,000 10,000 0 0
10,000
20,000
30,000
40,000
50,000
60,000
70,000
2007 AADT
As indicated in Table 7.4, the overall RMSE for the 2007 model is 34.6 percent, within acceptable Federal limits. TDOT has established an overall RMSE target of 30 percent. However, based on discussion with TDOT during the June 30, 2009 teleconference, it was
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determined that 30 percent was just a target and was not required as Federal standards indicate a RMSE range of 32 to 39 percent is within acceptable limits (according to the FHWA Model Validation and Reasonableness Checking Manual). Although the previous 2000 model indicated an overall RMSE of 23 percent, it is suspected that it was not as accurate due to the reduced amount of traffic counts available at that time. All volume groups within the 2007 model achieved a RMSE value close to or within Federal and/or TDOT targets. It should be noted that volume-over-count ratio charts relative accuracy and whether there is a systemwide under- or over-assignment, whereas RMSE measures assignment accuracy irrespective of whether these are generally over- or under-assignments. Achieving 0.96 in the 2007 model instead of 0.95 in the 2000 model is indicative of higher traffic assignments overall, which might not impact the overall percent error in a positive manner. The 0.96 overall volume/count ratio is reflective of the possibly low simulation of HBW trips, discussed earlier. Another consideration is that several outlying lower volume roads were added to the model near the boundary which could potentially negatively affect the 2007 RMSE results in particular.
Table 7.4
Root Mean Square Error (RMSE) by Volume Group Chattanooga TransCAD 2007
2000
TDOT Target
FHWA and New FDOT Guidelines and Standards
0-4,999
83.70%
73.10%
115.76
45-100
5,000-9,999
46.30%
33.60%
43.14
35-45
10,000-14,999
36.40%
18.10%
28.27
27-35
Count Range
15,000-19,999
25-30 21.70%
20,000-29,999
25.40%
25.38
30,000-39,999
16.90%
40,000-49,999
4.40%
15-27 15-25
12.10% 50,000-59,999
30.25 7.20%
10-20
60,000-69,999 10-19 70,000-79,999
15.50%
n/a
19.20
34.60%
23.40%
30.00%
79,999-89,999 Overall
32-39%
Table 7.5 summarizes the vehicle miles traveled (VMT) by model facility type, as well as the percent of VMT that falls within each model facility type compared to TDOT targets. With the exception of minor arterials, all of the facility types fall within or close to TDOT’s targets
64
Chattanooga TPO 2035 LRTP – Volume 3: Travel Demand Model Documentation and User’s Guide
for percent of VMT by facility type. In addition, the overall ratio of VMT to Highway Performance Monitoring System (HPMS) VMT is 1.06 (excluding external centroid connectors). While this general VMT distribution might be off for freeways and arterials, volume-over-count ratios show a favorable validation of these links. As a result, the only way to better match the VMT distribution would be to worsen the volume-over-count statistics.
Table 7.5
Vehicle Miles Traveled by Model Facility Type
Facility Type
Chattanooga 2007 Model VMT
Interstate
4,228,041 (31.4%)
Expressway
1,496,818 (11.1%)
Principal Arterial Divided
2,067,224 (15.4%)
TDOT Target 33-38%
27-33% Principal Arterial Undivided
835,239 (6.2%)
Minor Arterial
1,384,961 (10.3%)
18-22%
Collector
1,465,718 (10.9%)
8-12%
Ramp
215,118
n/a
One-Way
16,672
n/a
External Connectors
921,730
n/a
Centroid Connectors
827,412
n/a
Total
13,458,933
Comparison to Observed Speeds During November 2008, the TPO conducted travel time runs during the a.m. and p.m. peakperiods along all routes in their Congestion Management Plan (CMP). The results of these travel time runs were used to calculate average peak-period congested speeds. These observed speeds were then compared to the daily congested speeds in the model during the 2007 model validation process. Appendix D includes a map of the observed 2008 a.m. peakperiod congested speeds, as well as a map of the daily congested speeds from the 2007 model. As expected, the model speeds compared to the observed speeds are slightly different in some instances since the model speeds are daily and the observed speeds are peak-period. However, there was a significant improvement in congested speeds along interstates in the 2007 model as they were too low in the 2000 model.
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Chattanooga TPO 2035 LRTP – Volume 3: Travel Demand Model Documentation and User’s Guide
8.0 Summary and Conclusions Section 8.0 provides a bullet list summary of the 2007 model validation observations, as well as details on future model enhancements and data collection efforts planned by the TPO.
8.1 Summary of 2007 Model Validation Observations Below is a summary of 2007 model validation observations: •
The overall 2007 model is validating at an RMSE of 34.6 percent, within acceptable Federal limits;
•
The 2007 model is validating at a systemwide volume-to-count ratio of 0.96, within acceptable limits and improved since the 2000 model;
•
The correlation coefficient of observed counts to model volumes (R2) is performing well at 0.95, exceeding TDOT’s target of 0.88;
•
Eight of 10 screenlines are validating within acceptable limits;
•
The overall ratio of model VMT to HPMS VMT is 1.06;
•
Average trip lengths increased for some trip purposes and decreased for others, although HBW trip lengths did improve;
•
The percent of intrazonal trips attributed to HBW trips are now within a more reasonable range;
•
Congested speeds along the interstate and other higher facilities are improved compared to the 2000 model and observed congested speeds;
•
Overall, higher facilities are generally comparable to the 2000 model, however, minor facilities got worse in the 2007 model due to additional traffic count availability and network detail;
•
Overall, the 2007 model has more counts with almost 10 percent of the network having counts. As a result, the 2007 model includes improved accuracy and reliability of the model statistics;
•
Employment in the 2007 model is lower than in the 2000 model, resulting in lower commercial trips; and
•
As with all models, there is always room for improvement. However, this model should be sufficient for updating the 2030 LRTP to the year 2035.
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Chattanooga TPO 2035 LRTP – Volume 3: Travel Demand Model Documentation and User’s Guide
8.2 Future Model Enhancements Several enhancements are planned for the next generation of the Chattanooga travel demand model to be used for the next LRTP update scheduled for adoption in 2014. These enhancements, as well as the planned data collection efforts necessary to support these enhancements, are detailed below.
Data Collection In preparation for the next LRTP Update due for adoption in 2014, the TPO is planning for multiple data collection and compilation efforts over the next two years. Below are some of the data collection efforts planned:
68
•
Socioeconomic Data – Once the Census 2010 population and household data is released, likely in 2012, the TPO will use the data to develop the base year 2010 model socioeconomic data. In the meantime, the TPO will be providing guidelines to the counties and municipalities in the TPO region stating what socioeconomic data is required to assist with compiling the data. Additionally, proprietary employment datasets for the year 2010 may be evaluated for accuracy to determine the most appropriate data source for the Chattanooga region. In addition to year 2010, the TPO will be forecasting socioeconomic data to the horizon year for the next LRTP Update, likely year 2040.
•
Traffic Counts – During calendar year 2010, the TPO will be identifying and collecting traffic counts at key locations throughout the TPO to assist with validating the 2010 base year model as part of the next LRTP update. The traffic counts will be collected by vehicle class and 15-minute intervals in order to validate trips at the truck level and to include a new time-of-day component in the model.
•
External Origin and Destination Survey – In 2002, a roadside origin-destination intercept survey designed to obtain characteristics of travelers entering, exiting, and passing through the region from locations outside the CHCNGA study area was conducted. During the last 2030 LRTP Update, it was determined that the results from the 2002 external origin and destination survey were biased. As a result, during the last 2030 LRTP Update, as well as this current 2035 LRTP Update, the 2002 roadside origindestination intercept survey was not used within the TransCAD model. Therefore, the TPO intends to conduct a new external origin and destination survey during the fall of 2010. In the meantime, the TPO will be designing the sampling plan and survey instrument. The results of the 2010 external origin and destination survey will be used to validate the external model for the 2010 base year validation as part of the next LRTP update.
•
On-Board Transit Survey – As mentioned earlier, the TPO intends to conduct an onboard transit survey in order to validate a new mode choice/transit component in the TransCAD travel demand model. The TPO will be designing the sampling plan and
Chattanooga TPO 2035 LRTP – Volume 3: Travel Demand Model Documentation and User’s Guide
survey instrument in the spring/summer of 2010 with the survey being conducted in the fall of 2010. •
Household Travel Diary Survey – In 2002, a household travel diary survey was conducted to determine trip generation rates, average trip lengths, auto occupancy factors, and other characteristics used in model development and validation. Typically, household travel diary surveys are conducted every 10 years to accurately reflect travel characteristics of the region. Pending funding availability, the TPO intends to conduct a new household travel diary survey in calendar year 2011. The results of the 2011 travel diary survey will be incorporated into the new 2010 base year model for the next LRTP update.
•
Bicycle and Pedestrian Counts – If a nonmotorized component is added to the travel demand model prior to validating the 2010 base year model for the next LRTP Update, the TPO will collect bicycle and pedestrian counts. Currently, the TPO owns three bicycle and pedestrian counters and has begun collecting counts in key locations.
Travel Demand Model Enhancements The above mentioned data collection efforts will be used to incorporate several enhancements to the current CHCNGA TPO TransCAD model. These enhancements could potentially include the following additions to the TransCAD model prior to the next LRTP Update: •
Updated external model based on 2010 external data;
•
Updated trip generation structure based on 2011 household travel diary survey data;
•
New mode choice/transit component not previously included in the model to be used to forecast transit ridership;
•
New nonmotorized component not previously included in the model to be used to forecast bicycle and pedestrian trips;
•
New time-of-day component used to disaggregate daily trips into three to four time periods. This will improve the accuracy in calculating air quality emissions and is typically necessary for transit models; and
•
Validate truck trips in addition to total trips, whereas in the past, only total trips were validated.
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Chattanooga TPO 2035 LRTP – Volume 3: Travel Demand Model Documentation & User’s Guide
Appendix A: Network Project Lists
Chattanooga TPO 2035 LRTP – Volume 3: Travel Demand Model Documentation & User’s Guide
This Page Intentionally Left Blank
LRTP ID
I-75
Moore Rd.
SR 153
Chattanooga
Masters Rd.
STP-M-9202(51) Chattanooga Shallowford Rd.
Hixson Pike
Chattanooga
From
Chapman
Roadway
Jurisdiction
STP-M-9202(50) Chattanooga Shallowford Rd.
TIP ID
2002 Model Network Projects (Since 2000)
Wilcox
Noah Reid Rd.
Amnicola Hwy.
Hideaway Ln.
To
0.2
0.5
6.3
3.4
Length (miles)
Widening
Widening
Widening
Widening
Type of Project 2000
2001
2001
2002
Widen from 2 to 4 lanes
Widen from 4 to 6 lanes Widen from 2 to 5 lanes (4 thru lanes) Widen from 2 to 5 lanes (4 thru lanes)
2002
2002
2002
2002
No
No
No
No
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Construction Model Completion Network Regionally Year Full Description Year Exempt? Significant? Modeled?
TN07-LOC01
33041 TN01-MC011
STP-99-2
STP-98-3
21c
21d 58
96
98
111*
642210
650440
107637.02 101432
33015
DOT PIN
TN01-MC002 (TN)/ 101029 (TN)/ STP-99-1 (GA) 650430 (GA) STP-M-9202 (36)/ TN01-MC006 101557
STP-M-9202(52)
107*
102
TIP/STIP ID
LRTP ID
2009 Model Network Projects (Since 2002)
Hixson Pike
I-75
I-75
Chattanooga
Chattanooga
Chattanooga
Chattanooga
East Ridge (TN)/Catoosa County (GA)
Catoosa County
Catoosa County
Chattanooga Chattanooga
Chattanooga
Chattanooga
Ashland Terrace
Ringgold Rd.
SR 146
SR 146
Enterprise Blvd. SR 317 Connector (Proposed) Shallowford Rd.
3rd St./4th St.
I-75
SR 8/US 127
Chattanooga
Chattanooga
Roadway
Jurisdiction
Norcross Rd.
CR 40
I-75
Lakeview Dr.
Knollwood Drive
Frawley Rd.
SR 3/US 41
I-75
Apison Pike @ Old Lee Hwy. West of Center St.
I-75 Enterprise South Interchange Standifer Gap
1.3
0.03
0.6
1.3
0.6 1.2
1.1
Enterprise South Blvd. cul-desac
Enterprise Pkwy. Fork
3.1
1.2
2.4
1.4
0.5
1.1 mile south of SR 2/US 11
SR 317
Dallas Hollow Rd.
Suck Creek Rd.
To
Broad St./Georgia Ave.
Lindsay
New Interchange at Mile 9 (Enterprise South)
SR 317
Shallowford Rd.
Hideaway Ln.
US 27
From
Length (miles)
Widen from 2 to 4 lanes
New Interchange at Mile 9 (Enterprise South)
Widen from 4 to 8 lanes
Widen from 4 to 6 lanes
Widen from 2 to 6 lanes
Widen from 4 to 6 lanes
Full Description
Widening
Widening
Widening
Widening
New Construction Widening
Widen from 2 to 4 lanes
Widen from 2 to 5 lanes (4 through lanes)
Widen from 2 to 4 lanes
Widen from 2 to 4 lanes, including bridge reconstruction
New 4-lane facility Widening from 2 to 5 lanes (4 thru lanes)
New Construct new 4-lane roadway from Enterprise Construction Pkwy to existing cul-de-sac
Widening
New Interchange
Widening
Widening
Widening
Widening
Type of Project
2008
2008
2009
2009
No
No
No
2009 (construction 2009 (remove from won't be 2009 network for air complete until quality) 2010)
No No
No
No
No
No
No
No
No
Yes
Yes
Yes
Yes
Yes Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Regionally Exempt? Significant?
No
2009 2009
2009
2007 & 2009
2007 & 2009
2007 & 2009
2007 & 2009
2007 & 2009
2007 & 2009
Model Network Year
2009 (construction 2009 (remove from won't be 2009 network for air complete until quality) 2010)
2009 2008
2008
2003
2007
2007
2005
2005
2005
Construction Completion Year
Yes
Yes
Yes
Yes
Yes Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Modeled?
33020
TN01-MC007
101
108
178
170****
142***
141***
140***
139***
138***
137***
136***
135***
134***
133***
132***
131***
130***
129***
128***
126
33027
33045
TN01-MC007
94
108
88 91
33025
33043
17b
21e e 23
33042
17a
11
10
5
4
621530
81908.2
21b
3
33042
In FY '08-'11 TIP (Amended Feb '09)
17a
15
LRTP ID
TN
Chattanooga (Hamilton Co.) Chattanooga (Hamilton Co.)
Collegedale (Hamilton Co.) Chattanooga ((Hamilton a to Co.) Co ) Fort Oglethorpe Chattanooga (Hamilton Co.) Catoosa Co. Chattanooga (Hamilton Co.) Chattanooga (Hamilton Co.) Chattanooga (Hamilton Co.) Chattanooga (Hamilton Co.) Chattanooga (Hamilton Co.) Chattanooga (Hamilton Co.) Chattanooga (Hamilton Co.) Chattanooga (Hamilton Co.) Chattanooga (Hamilton Co.) Chattanooga (Hamilton Co.) Chattanooga (Hamilton Co.) Chattanooga (Hamilton Co.) Chattanooga (Hamilton Co.) Chattanooga (Hamilton Co.) Chattanooga (Hamilton Co.) Chattanooga (Hamilton Co.) Chattanooga (Hamilton Co.) Chattanooga (Hamilton Co.)
TN
Chattanooga/ Collegedale (Hamilton Co.)
TN
TN
TN
TN
TN
TN
TN
TN
TN
TN
TN
TN
TN
TN
TN
TN
US 27/Olgiati Bridge
SIA Road for VW (Industrial Access Rd.)
Street O
Street N
Street M
Street L
Street K
Street J
Street I
Street H
Street G
Street F
Street E
Street D
Street C
Street B
Street A
Hickory Valley Rd.
TN
TN
Shallowford Rd.
US 27/I-124 Three Knotch Rd. SR 320/East Brainerd Rd.
Enterprise te p se Parkway a ay Lakeview Dr.
SR 317/Apison Pike
SR 317/Apison Pike
Central Ave. Extension
Gadd Rd.
SR 151/Alabama Hwy.
Deitz Rd.
US 27
Shallowford Rd.
I-75
Enterprise Pkwy.
Termini
SR 321
I-75
To
Riverfront Pkwy.
Street N Enterprise Boulevard/Discovery Dr.
Middle Street
Sindey St
Chestnut
Street D
Street D
Street D
Street D
Street F
Street D
Street F
I-24
Street A
Street A
Street A
Gunbarrel Rd. Enterprise Parkway Extension
East of Graysville Rd.
I-24 Boynton Rd.
Hickory c o y Valley a ey Road oad Page Rd.
SR 321
Old Lee Hwy.
3rd St.
Norcross Rd.
Holcomb Rd.
Gunbarrel Rd. North of Tennessee River Bridge SR 146/Cloud Springs Rd.
Manufacturer's Rd.
SR 58
Street N
Middle Street
Broad st.
W 26th st.
Chestnut
Street E
W 28th st.
Street F
Street H
W 28th st.
Broad st
Chestnut
Street E
Street A
Street C
Highway 58
Jenkins Rd.
Bel Air Rd.
East Brainerd Rd. 1 mile south of Highway 58 Cross St. South of Tennessee River SR 2
SR 321
Riverside Drive
SR 153
US 41/Nashville St.
Jenkins Rd. SR 8/Signal Mountain Blvd. Reeds Bridge Rd./Boynton Rd.
Enterprise Pkwy./I-75 Enterprise Blvd./Pkwy. Interchange Fork 1.1 Mi south of SR 0.2 Mi north of SR 2/US 2/US 11 11
Old Lee Hwy.
SR 17
SR 317/Bonny Oaks Drive
SR 317/Apison Pike
From
Road Name
TN
TN
TN GA
TN GA
TN
TN
GA
GA
TN
TN
TN
TN
TN
TN
State
Fort Oglethorpe Ringgold (Catoosa Co.) Chattanooga (Hamilton Co.) Chattanooga (Hamilton Co.)
Chattanooga Chattanooga (Hamilton Co.)
Chattanooga
Chattanooga
Chattanooga Chattanooga/Colle gedale
City (County)
Jurisdiction
2015 Model Network Projects (Since 2009)
Widening
New Roadway
New Roadway
New Roadway
New Roadway
New Roadway
New Roadway
New Roadway
New Roadway
New Roadway
New Roadway
New Roadway
New Roadway
New Roadway
New Roadway
New Roadway
New Roadway
Widening
Widening
Widening
Widening Widening
New e Alignment g e t Widening
Widening
Widening
Widening New Roadway (Extension)
Widening
Widening Widening/ Realignment
Widening
Widening
New Construction
Widening
Widening
Type of Project
2.3 Widen from 4 to 6 lanes
0.1
New two lane road
0.3
0.1
0.1
0.2
0.1
0.2
0.2
0.1
0.3
0.4
0.6
0.4
0.1
0.7
1.1
1.0
1.9
1.5 0.3
0.6 06 0.7
4.0
2.1
0.6
0.2
1.7
2.1
2.7
1.1
1.3
Industrial access road for Volkswagen
New two lane road
New two lane road
New two lane road
New two lane road
New two lane road
New two lane road
New two lane road
New two lane road
New two lane collector road
New two lane collector road
New two lane collector road
New two lane road
New two lane road
New two lane road
Widen from 2 to 4 lanes
Widen from 2 to 4 lanes Widening from 2 to 5 lanes (4 thru lanes)
Widen from 4 to 8 lanes Widen from 2 to 4 lanes
Widen from 2 to 4 lanes
Widen from 2 to 4 lanes
Widen from 2 to 4 lanes
2-lane extension
Widen from 2 to 4 lanes
Widen from 2 to 4 lanes Widen from 2 to 4 lanes with turn lanes as needed
Widen from 4 to 8 lanes
Widen from 4 to 8 lanes Widening from 2 to 5 lanes (4 thru lanes)
Construct new 4-lane roadway (Enterprise Pkwy.) from Enterprise Pkwy./I-75 Interchange to Enterprise Blvd./Pkwy. Fork
2.17
4.9
Widen from 2 to 4 lanes (already four lanes either direction of listed termini specifically from Silverdale Road east to I-75 and from Preservation Drive west to SR 17) Widen from 2 to 4 lanes
Length (miles)
Project Description
2010
2010
2010
2010
2010
Construction Completion Year
2015
2015
2015
2015
2015
2015
2015
2015
2015
2015
2015
2015
2015
2015
2015
2015
2015
2015
2015
2015
2015 2015
2015 0 5 2015
2015
2015
2015
2015
2015
2015
2015
2011 E+C & 2015 2011 E+C & 2015 2011 E+C & 2015
2011 E+C & 2015 2011 E+C & 2015
Model Network Year
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No No
No o No
No
No
No
No
No
No
No
No
No
No
No
No
Exempt?
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes Yes
Yes es Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Regionally Significant?
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes Yes
Yes es Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Modeled?
TN
TN
Chattanooga (Hamilton Co.)
Chattanooga (Hamilton Co.)
104
106
116
107
TN
TN
TN
Chattanooga (Hamilton Co.)
71
Chattanooga (Hamilton Co.) Chattanooga (Hamilton Co.)
TN
Chattanooga (Hamilton Co.)
64
Yes
TN
33
TN
TN
TN
39
Chattanooga (Hamilton Co.) Chattanooga (Hamilton Co.)
Chattanooga (Hamilton Co.) Chattanooga (Hamilton Co.)
20
18
TN
Chattanooga (Hamilton Co.)
Yes
15
GA
TN/GA
Ringgold (Catoosa Co.)
Ringgold
Yes
6
5
LRTP ID
In FY '08-'11 Jurisdiction TIP (Amended Feb City (County) State '09)
2025 Model Network Projects (Since 2015)
Hickory Valley Rd
Central Ave.
3rd St./4th St.
Mahan Gap Rd./SR 312 I-75 northbound to I-24 westbound lane extension
Jenkins Rd.
East Brainerd Rd.
Wauhatchie Pike
Snow Hill Rd.
US 11/US 64/Lee Hwy.
SR 317/Bonny Oaks Drive
SR 151/Alabama Hwy. SR 321 (TN)/SR 151 (GA)/Ooltewah-Ringgold Rd.
Road Name
Standifer Gap Rd
3rd St.
Lindsay St.
Beyond Belvoir Road Overpass
SR 58
Standifer Gap
Banks Rd.
US 11
I-75
McCutcheron Rd.
SR 17
Lee Hwy.
Holcomb Rd.
From
To
Enterprise Parkway
I-24
Hampton St.
Snow Hill Rd.
Shallowford Rd.
US 41/US 64 SR 321/OoltewahRinggold Rd.
SR 312/Mahan Gap Rd.
SR 317
I-75
US 41/US 76
US 41/Nashville St.
Termini
Widening
Operational (Center Turn Lane)
Widening & Extension
Interchange Reconstruction
Widening
Widening
Widening
Widening
Widening
Widening
Widening
Widening
Widening
Type of Project
From 1 to 2 lanes Widening of 3rd/4th from Lindsay St. to Hampton St. to twoWiden from 4 to 5 lanes to include center turn lane Widen from 2 to 4 lanes
Widen from 2 to 4 lanes
Widen from 2 to 4 lanes
Widen from 2 to 4 lanes Widen from 2 to 4 lanes
Widen from 2 to 4 lanes Widen from 2 to 4 lanes
Widen from 2 to 4 lanes Widen from 2 to 4 lanes (already four lanes either direction of listed termini specifically from Silverdale Road east to I-75 and from Preservation Drive west to SR 17)
Project Description Widen from 2 to 4 lanes with turn lanes as needed
1.4
1.9
1.2
2.0
0.7
0.8
1.6
2.8
6.7
1.6
5.1
12.1
1.7
Length (miles)
2025
2025
2025
2025
2025
2025
2025
2025
2025
2025
2025
2025
2025
Model Network Year
No
No
No
No
No
No
No
No
No
No
No
No
No
Exempt?
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Regionally Significant?
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Modeled?
East Ridge Chattanooga (Hamilton Co.) Chattanooga (Hamilton Co.) Chattanooga (Hamilton Co.) Chattanooga (Hamilton Co.) Chattanooga (Hamilton Co.)
38
92
81a
73
70
67
63
55
54
East Ridge Chattanooga (Hamilton Co.) Chattanooga (Hamilton Co.)
Fort Oglethorpe
35
28b
Rossville Chattanooga (Hamilton Co.)
Chattanooga (Hamilton Co.) Chattanooga (Hamilton Co.) Chattanooga (Hamilton Co.)
24_25
19
13b
13
8
LRTP ID
TN
TN
TN
Dupont Pkwy. Extension
Goodwin Rd. Extension
Moore Rd.
SR 58
SR 153
TN
Standifer Gap
TN
SR 153
Dodson Ave.
SR 2/Battlefield Pkwy. Camp Jordan Pkwy. Extension
Graysville Road
McFarland Ave.
Amnicola Hwy.
Shallowford Rd
Shallowford Rd.
Central Ave. Extension
Road Name
TN
TN
TN
TN
GA
TN
GA
TN
TN
TN
In Jurisdiction FY '08-'11 TIP (Amended Feb '09) City (County) State Chattanooga (Hamilton Co.) TN
2035 Model Network Projects (Since 2025)
SR 153
Gunbarrel
Ringgold Rd.
Champion Rd.
SR 319/Hixson Pike
Walker Rd.
Gothard Rd.
Wilcox Blvd.
Camp Jordan Rd.
South Cedar Ln.
E Brainard
Chickamauga Ave.
Riverport Rd.
Airport Rd
Airport Rd.
Lee St.
From
SR 312
SR 17/SR 58
Bill Reed Rd.
Dayton Blvd.
Glass St.
Gunbarrel Rd.
I-75
Dug Road
SR 341
SR 153
Jersey Pike
N Moore Rd
SR 193
To
Hixson Pike
Hamilton Place Blvd.
North Terrace Rd.
Termini
New Roadway
New Roadway
Widening
Widening
Widening
Widening
Widening
Widening
New Roadway
Widening
Widening
Widening
Widening
Widening
Widening
New Roadway
Type of Project
Widen from 2 to 4 lanes Widen from 2 to 4 lanes Widen from 4 to 6 lanes New 2-lane facility (extension) Widen from 2 to 4 lanes Widen from 4 to 6 lanes Widen from 2 to 4 lanes Widen from 4 to 6 lanes Widen from 4 to 6 lanes Widen from 2 to 4 lanes New 4-lane facility (extension) New 2-lane facility (extension)
Widen from 2 to 4 lane Widen from 4 to 6 lanes
Project Description New 2-lane facility (extension) Widen from 2-4 lanes from Airport Rd to West of SR 153 at Palmer Rd or TDOT Bridge Replacement Project shallowford RD over SR 153 - 4 lanes
1.2
0.3
0.9
8.7
5.9
1.6
1.5
0.8
2.5
5.0
2.0
6.6
3.3
0.9
0.6
1.0
Length (miles)
2035
2035
2035
2035
2035
2035
2035
2035
2035
2035
2035
2035
2035
2035
2035
2035
Model Network Year
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
Exempt?
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Regionally Significant?
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Modeled?
Chattanooga TPO 2035 LRTP – Volume 3: Travel Demand Model Documentation & User’s Guide
Appendix B: Technical Memorandum #1
Chattanooga TPO 2035 LRTP – Volume 3: Travel Demand Model Documentation & User’s Guide
This Page Intentionally Left Blank
Memorandum TO:
Bob Rock, TDOT Jerry Yuknavage, TDOT Tyrhonda Edwards, GDOT
CC:
Angie Midgett, TDOT
FROM:
Melissa Taylor, CHCNGA TPO Keli Paul, AICP, Cambridge Systematics
DATE:
September 18, 2008
RE:
Model Certification Submittal #1: Outline of TransCAD Model Assumptions Chattanooga-Hamilton County/North Georgia 2035 LRTP Update
Effective March 1, 2008, the Tennessee Department of Transportation (TDOT) Long Range Planning Division, Systems Planning and Policy Office, implemented a Division Procedure for the MPO model approval process. On August 20, 2008, the RPA met with its consultants along with TDOT, GDOT, and CARTA to discuss the TransCAD modeling efforts for the CHCNGA 2035 LRTP Update. It was agreed at that time that the following four submittals would be provided to TDOT and GDOT as part of TDOT’s model approval process: 1. Outline of the model, planning assumptions to date, and model validation worksheet template; 2. Year 2007 and 2035 socioeconomic data files (TransCAD and GIS) for the TPO region, including any maps, graphs, charts, or tables developed as part of the RPA’s internal review; 3. Populated validation worksheet upon completion of draft validated model. This worksheet will include statistics for Trip Generation, Trip Distribution, Mode Choice (if applicable), and Traffic Assignment. If the assumptions included in submittal #1 change as part of the validation process, they will be documented and submitted for approval at this time; and 4. Full model documentation report and user’s guide, along with all TransCAD files, after the draft LRTP has been documented. This technical memorandum constitutes Submittal #1 defined above. Below is an outline of modeling inputs and structure for each step of the traditional four-step modeling process. Further details addressing each output statistic or map required as a result of the TDOT Division Procedure are attached, both for the previous 2000 model and what is anticipated as part of the 2007 model. The attached table also incorporates recommendations from the report developed by the University of Tennessee, Center for Transportation Research, titled “Minimum 2457 Care Drive, Suite 101 Tallahassee, FL 32308 tel 850 219 6388
www .ca msys .co m
fax 850 219 6389
Travel Demand Model Calibration and Validation Guidelines for State of Tennessee.” This report is also referenced in the TDOT Division Procedure. 1.0 TRIP GENERATION (includes Network data) 1.1 Network Data – The base year model network is being updated from year 2000 to 2007. 1.1.1 Network Refinement - Several roads are being added to the model network to more accurately depict travel patterns and to assist with splitting several of the larger traffic analysis zones (TAZs). TRIMS and Roadway Characteristics (RC) data were obtained from TDOT and GDOT, respectively, to assist with reviewing the link characteristics (facility type and number of lanes) currently in the model network. In addition, several windshield surveys were conducted to obtain area type, facility type, and number of lanes data for those roads being added to the model. 1.1.2 Traffic Counts – Daily traffic counts will also be updated in the 2007 network using available count data from TDOT, GDOT, Hamilton County and the City of Chattanooga. Count data was not available from Catoosa, Dade, or Walker Counties. Supplemental 24-hour count data by vehicle classification will be collected in late September 2008 to supplement model validation efforts and assist with evaluating existing conditions for the Congestion Management Plan (CMP). Transportation Projects – Several lists of capacity-adding transportation projects included in each model year are being or will be developed as part of the LRTP update process. Each of these project lists will be provided upon completion to TDOT and GDOT, as well as the entire Interagency Consultation Committee (ICC). They are as follows: •
Year 2007 Projects - Projects that completed construction between the years 2000 and 2007 (currently being developed)
•
Existing-Plus-Committed (E+C) Projects - Projects that are expected to complete construction between the years 2008 and 2011 (i.e. those in the Transportation Improvement Program (TIP)) (currently being developed)
•
Year 2035 Financially Feasible Plan Projects – Projects funded in LRTP
•
Year 2025 Funded Projects – Interim year 2025 funded projects
•
Year 2015 Funded Projects – Interim year 2015 funded projects
1.2 Socioeconomic Data – The Regional Planning Agency (RPA) is currently developing the 2007 and 2035 socioeconomic data for the entire TPO region. Upon completion, Cambridge Systematics (CS) will conduct a thorough review of the data at the TAZ level, including the development of population, household, employment, hotel-motel, and school enrollment density maps. The TransCAD and GIS files, as well as the maps and any tables, charts, or graphs, will be provided to TDOT and GDOT for review as part of Submittal #2.
-2-
1.3 TAZ Refinement – The RPA is taking this opportunity to refine the TAZ structure in the current TransCAD model. Many of the TAZs are rather large in the outlying areas. Additional network detail being added to the model will also effect the TAZ structure, including external zones. 1.4 Travel Survey Data – During the 2030 LRTP Update adopted in 2005, the Chattanooga Household Travel Diary Survey conducted in 2002 was used to determine trip production rates for person trips. The Federal Highway Administration (FHWA) Quick Response Freight Manual (QRFM) was used to supply trip production rates for the truck trip purposes. Trip attraction rates were borrowed from the Northeast Regional Planning Model (NERPM) in Jacksonville, FL, as local data was not available. These same trip production and attraction rates will be used for this model update. Although the percent split of Internal-External (IE)/External-External (EE) trips at each external station was developed from the Chattanooga Urban Area Origin-Destination Study conducted in 2002, it was found that the original MinUTP model had more reasonable IE/EE splits due to how the O-D study was conducted. With the exception of new external stations, the updated model as part of the 2035 LRTP Update will use the same IE/EE splits from the MinUTP model. Any new external stations, which will likely be minor roads with low traffic counts, will likely assume 100 percent IE trips. 1.5 Trip Generation Method – During the 2030 LRTP Update adopted in 2005, the 2002 Chattanooga Household Travel Survey data was evaluated to determine what variables impact travel patterns the most in the Chattanoga region. As a result, a crossclassification method based on auto availability and children per household was implemented. This same method will be using during this update. 1.6 Trip Purposes – The current TransCAD model includes the following trip purposes, which will remain the same during this update: •
Home-Based Work (HBW)
•
Home-Based School (HBSchool)
•
Home-Based Shop (HBShop)
•
Home-Based Social/Recreation (HBSR)
•
Home-Based Other (HBO)
•
Non-Home Based (NHB)
•
Light-Duty Truck (LDTK)
•
Medium-Duty Trucks (MDTK)
•
Heavy-Duty Trucks (HDTK)
1.7 Special Generators – The current TransCAD model includes special generators at the airport, the University of Tennessee at Chattanooga, Chattanooga State College, and
-3-
Chester Frost National Park. No special generators will be assumed at the beginning of 2007 model validation effort, however, it is anticipated that some special generators may eventually be necessary. 2.0 TRIP DISTRIBUTION 2.1 Friction Factors - The friction factor file used in the new CHCNGA 2000 TransCAD model is similar to the file used in the CHCNGA 2000 MINUTP model. The key difference is the number of trip purposes. Since separate friction factors were not available for the expanded home-based other purposes, the same home-based other friction factors were used for home-based school, home-based shop, and home-based social recreation trips. Gamma functions from the Quick Response Freight Manual were used for truck purposes. These same friction factors will be assumed for the 2007 model and future years. If time permits, the friction factors may be calibrated. 2.2 Terminal Times – Terminal times were used in the 2000 model and will also be used in the 2007 model. 2.3 K-Factors – K-Factors were used in the 2000 model. To improve the Georgia/Tennessee State Line screenline in the 2000 model, a 0.25 K-Factor was added from zones in Georgia to zones in Tennessee. To improve the Tennessee River Crossing screenline, a 0.25 K-Factor was added to zones from the north side of the bridges to the rest of the model region. No K-Factors will be assumed at the beginning of the 2007 model validation process, however, they may be added if necessary. 3.0 MODE CHOICE The current TransCAD model for Chattanooga does not include a mode choice/transit component. Instead, it includes an auto occupancy model that converts person trips to vehicle trips using auto occupancy factors by trip purpose derived from the 2002 Household Travel Diary Survey conducted in the Chattanooga region. Dependent upon available data, the RPA was considering adding a mode choice/transit pathbuilding component to the TransCAD model as part of the 2035 LRTP Update. However, since the August 20, 2008 modeling workshop referenced above, it was determined that there is not enough data currently available to validate a mode choice/transit pathbuilding model. As a result, the RPA, in coordination with CARTA, is considering conducting an on-board transit survey in the Spring of 2009 with the intention of building a mode choice model in the Summer and Fall of 2009. However, it will not be included as part of the 2035 LRTP Update. Therefore, the current auto occupancy model will remain in place for the 2035 LRTP Update. 4.0 TRIP ASSIGNMENT 4.1 Time-of-Day – Currently, the Chattanooga model does not include a true time-of-day component. Instead, peak hour factors based on the temporal distribution from the 2002 Household Travel Diary Survey are applied to the daily volumes after the assignment process to achieve AM and PM peak hour volumes. There is the potential
-4-
for adding a true time-of-day component to the Chattanooga 2007 model, but not in time for the 2035 LRTP Update. NEXT STEPS Below is a list of the next information to be provided to TDOT and GDOT for review and approval upon completion: •
2007 and 2035 socioeconomic data (currently expected in November 2008)
•
List and corresponding map of capacity-adding transportation projects added to the 2000 model to update to 2007
•
Populated validation worksheet once validation complete
As noted earlier, once the modeling efforts and draft LRTP document have been completed, full model documentation, including a user’s guide and all model files, will be provided to TDOT and GDOT. As discussed during the modeling workshop held on August 20, 2008, please provide any comments back to the RPA within 10 days, if not sooner. We thank you in advance for understanding our time constraints and look forward to coordinating with you throughout the development of our model and LRTP. If you have any questions about the model, please do not hesitate to contact Melissa Taylor at the RPA via email at
[email protected] or phone at (423) 757-0077.
Attachments: Table of TDOT Validation Requirements Empty Validation Worksheet
-5-
Attachment #1
Model Validation Documentation Requirements Specified in TDOT Division Procedure: MPO Model Approval and “Minimum Travel Demand Model Calibration and Validation Guidelines for State of Tennessee,” University of Tennessee, Center for Transportation Research
Attachment #1: MPO Model Certification Requirements CHCNGA 2035 LRTP TDOT's MPO Model Approval Requirements (Effective 3/1/08) Socioeconomic Data TAZ Maps with corresponding existing and future SE data, including external stations Person trips/household by purpose Travel Survey Data
Source, year, and type of travel survey information
If no survey, provide source of trip data Network Data Provide files (networks, turn penalties/prohibitors, speed/cap, FT codes) Table of significant projects added to network by model year Explanation of how MPO dealing with crossborder traffic Trip Generation
Description of trip generation method (P/A, O/D, Special Generators; Cross-Class, Regression, or Discrete Choice)
Description of trip purposes
Description of how EE and EI trips addressed Whether trip rates developed for vehicle and/or person trips Special generators (how and where) Trip Distribution Files (friction factors, terminal time, and Kfactors) Trip length by trip purpose for base and future year Comparison of HBW mean trip length compared to Census JTW mean trip length Trip Length Frequency Distribution (TLFD) by Trip Purpose Compared to Census JTW and Household Travel Survey (Charts) Area-to-Area Flow of Trips
Type of Submittal
Source of Requirement
PDF Maps Validation Worksheet
TDOT*
Text (overview provided in Submittal #1) Text (overview provided in Submittal #1)
2000 Model
2007 Model
TDOT*
Household travel diary survey (2002) used to determine trip generation rates, average trip lengths, auto occupancy factors, and other characteristics used in 2000 model development and validation. Percent IE/EE splits were calculated from the Chattanooga Urban Area Origin-Destination Study conducted in 2002. However, it was determined that these percentages were not reliable as the interstate surveys were conducted on ramps at interchanges and rest areas. Vehicles were not pulled off to the side of the road on the mainline interstate segments where most EE trips occur. The vehicles that were surveyed were already stopping at the interchange or rest area. Therefore, the results provide a significant bias towards IE trips and EE trips are underestimated. The percent IE/EE splits from the origin and destination survey were subsequently compared to the old 2000 MINUTP model and it was determined that the old 2000 MINUTP model percent splits appeared more reasonable.
Will need to modify TAZ structure to account for new minor roads added that may represent external stations; if so, will assume 100% IE split.
TDOT*
QRFM used for truck trip production rates; NERPM for attraction rates
U Tenn**
Files
TDOT*
Excel Table
TDOT*
Text
TDOT*
K-factor and screenline at state line
Determine during validation
TDOT*
Cross-Classification method based on auto availability and children per household; Trip production rates for HBW, HBSCHOOL, HBSHOP, HBSR, HBO, and NHB calculated using 2002 HH Travel Diary Survey; Truck production rates from QRFM; Attraction rates from NERPM; Special generators included
same
TDOT*
HBW, HBSCHOOL, HBSHOP, HBSR, HBO, NHB, LTTK, MDTK, HDTK
same
Text
TDOT*
The MINUTP splits were used as a starting point and were later modified during the validation process. The percent IE trips were applied to the 2000 AADT to calculate the total number of IE trips at each external zone for the TAZ geography file. The EETRIPS input matrix file is generally the residual left after estimating IE trips in the TAZ geography file. The percentage of EE trips was applied to the AADT per external zone and then distributed from each origin zone to each destination zone using distribution patterns from the old MINUTP 2000 model EETRIPS file. For external zones added to the TransCAD model, and not in the MINUTP model, it was assumed that 100 percent of these trips were EE trips since these were low volume roadways.
Adding new external stations; For external zones added to the TransCAD model, assume that 100 percent of these trips are EE trips since these were low volume roadways.
Text
TDOT*
Person trips
Text
TDOT*
Files Validation Worksheet Validation Worksheet Validation Worksheet (add charts) Map
TDOT*
Text (overview provided in Submittal #1) Text (overview provided in Submittal #1)
TDOT* TDOT*
U Tenn** U Tenn**
same Determine during Yes; Airport, UTC, Chatt State College, Chester Frost National Park validation
Attachment #1: MPO Model Certification Requirements CHCNGA 2035 LRTP TDOT's MPO Model Approval Requirements (Effective 3/1/08)
Were friction factors in gravity model kept constant between base and future years?
Were terminal times used?
Were K-factors used and if so, what was the basis? Mode Split Description of mode split and choice analysis method (i.e. nested logit?) Were vehicle occupancy factors by trip purpose used to convert person trips to vehicle trips? Were they kept constant between years? Source? What network model coding logic was used to code access to transit in the network? Trip Assignment Files (loaded network, summary table including estimated link vols & costs, text file with user inputs and model outputs) Comparison of screenline vols with counts (2 N/S, 2 EW) Comparison of cutline, screenline, and cordon line vols with counts
Type of Submittal
Text (overview provided in Submittal #1) Text (overview provided in Submittal #1)
Text (overview provided in Submittal #1)
Percent Difference in Peak Hour Volume by FT Percent RMSE by Link Volume Group Scatter Plot of Assigned vs. Observed Link Traffic Volume Correlate coefficient by link volumes Overall Performance VMT, VHT, and average speed for entire system and by FT VMT per capita (VMT/population) Final Files (complete datasets) Final Documentation (complete model validation report, including user's guide)
TDOT*
TDOT*
TDOT* TDOT*
2000 Model Yes. The friction factor file used in the new CHCNGA 2000 TransCAD model is similar to the file used in the CHCNGA 2000 MINUTP model. The key difference is the number of trip purposes. Since separate friction factors were not available for the expanded home-based other purposes, the same home-based other friction factors are used for home-based school, home-based shop, and home-based social recreation trips. Also, as discussed, gamma functions from the Quick Response Freight Manual were used for truck purposes.
2007 Model
same
Yes same Yes; To improve the Georgia/Tennessee State Line screenline in the CHCNGA 2000 TransCAD model, a 0.25 K-Factor was added from zones in Georgia to zones in Tennessee. To improve the Tennessee River Crossing screenline, a 0.25 K-Factor was added to zones from the north side of Determine during the bridges to the rest of the model region. validation
Text (n/a)
TDOT*
n/a
n/a
Text (overview provided in Submittal #1)
TDOT*
Yes; Yes; Source is HH Travel Survey
same
Text (n/a)
TDOT*
n/a
n/a
Files Validation Worksheet Validation Worksheet Text (overview provided in Submittal #1)
TDOT*
TDOT*
No
same
TDOT*
Peak hour factors applied to achieve temporal distribution based on 2002 Household Travel Diary Survey
same
Was time-of-day assignment performed? If so, details. If no time-of-day assignment, how were 24-hour vols converted to peak hour vols? What Text (overview conversion factors used? Relationship between provided in peak hour & 24-hour vol? Submittal #1) Validation Fraction of total VMT assigned to IZ and centroid connector trips? Is it reasonable? Worksheet (add) Traffic counts on 10% of regionwide highway segments by functional calss (freeways and principal arterials at a minimum & screenlines) Percent Differences in Daily Volume by FT and screenline
Source of Requirement
Table Validation Worksheet Validation Worksheet (add) Validation Worksheet Validation Worksheet (add chart) Validation Worksheet (add) Validation Worksheet Validation Worksheet (add) Files PDF of Final Report
TDOT* TDOT*
TDOT*
U Tenn** U Tenn** U Tenn** U Tenn**
U Tenn** U Tenn**
TDOT* TDOT* TDOT* TDOT*
Attachment #2
Model Validation Worksheets (Template – Not Populated with 2007 Statistics)
0
Commercial Vehicles Light-Truck Medium-Truck Heavy-Truck Internal-External External-External SOV HOV Light-Truck Heavy-Truck TOTAL
% by Productions #DIV/0! #DIV/0! #DIV/0! #DIV/0! #DIV/0!
*2 FHWA Target
*2 New FDOT Guidelines
Person Trips / Household Region Chattanooga (TransCAD) Chattanooga (TransCAD) Chattanooga (MINUTP) *1 TDOT Target
Persons per Household Internal Trips per Household Internal Trips per Person Internal Trips per Employee Employees per Person Total Population Total Households Total Employment
Unit of Measure
Year 2007 2000 2000
#DIV/0! 0.00 0.00 0.00 #DIV/0! 0 0 0
n/a
8.00 to 10.00
Person Trip/HH 0.00 9.44 7.44 8.50 to 10.50
2.50 9.44 3.78 5.18 0.73 395,061 158,055 287,918
2007 2000 Chattanooga (TransCAD)
Aggregate Trip Rates & Socioeconomic Summaries
#DIV/0! #DIV/0! #DIV/0! #DIV/0! #DIV/0! 0 #DIV/0! 0 #DIV/0! #DIV/0! #DIV/0! #DIV/0! 0 #DIV/0!
0 0 0 0 0 0
Productions
Home-Based Work Home-Based School Home-Based Shop Home-Based Socrec. Home-Based Other Non Home-Based
Purpose
2007 Chattanooga 2007 (TransCAD)
Comparison of Total Trips by Purpose
Trip Generation
TEMPLATE 9/18/2008
Chattanooga 2007 MODEL VALIDATION SUMMARY
Run# DATE: Description:
Productions % by Productions 212,113 12.72% 85,068 5.10% 159,420 9.56% 92,919 5.57% 289,013 17.33% 434,513 26.06%
2000 Chattanooga (TransCAD)
Memphis 2.65 8.20 3.09 6.41 0.51 761,346 310,412 457,796
2004
2000 Montgomery*5 2.68 8.64 3.23 4.91 0.66 1,181,701 416,830 604,578
163,330 9.80% 120,286 73.65% 31,580 19.34% 11,464 7.02% 0 230,906 13.85% 30,025 0.00% 0.00% 0.00% 0.00% 1,667,282 100.00%
0
0 0 0 0 0 0
Nashville 2.56 8.59 3.36 4.86 0.69 1,206,665 471,298 833,862
2002
Attractions
Unbalanced
2004
2000
Knoxville 2.45 8.40 3.43 5.70 0.60 299,180 111,793 196,799
2000
Savannah 2.53 7.66 3.03 5.54 0.55 232,011 91,834 127,000
2001
TDOT Target*1 n/a 8.5-10.5 n/a n/a n/a
100.00%
100.00%
100.00%
13.00% 3.00%
Memphis Montgomery 25.15% 16.00% 11.02% 7.17% 39.00% 7.67% 28.10% 18.00% 20.89% 11.00%
8.82%
26.42% 8.79%
39.18%
Nashville 16.79%
2004
New FDOT Guidelines*2 2.0-2.7 8.0-10.0 3.3-4.0 n/a n/a
22-31%
47-54%
TDOT Target *1 18-27%
FHWA Target*3 n/a 8.0-14.0 3.5-4.0 n/a n/a
New FDOT Guidelines*2 12-24% 5-8% 10-20% 9-12% 14-28% 20-33% *4 FHWA Target *3
= Statistics in green-colored cells will be updated when 2007 validated model is ready.
Home-Based Work Home-Based School Home-Based Shop Home-Based Socrec. Home-Based Other Non Home-Based Commercial Vehicles Light-Truck Medium-Truck Heavy-Truck TOTAL
Purpose
Intrazonal Travel
Home-Based Work Home-Based School Home-Based Shop Home-Based Socrec. Home-Based Other Non Home-Based Commercial Vehicles Light-Truck Medium-Truck Heavy-Truck Internal-External TOTAL
Purpose
2000 Chattanooga (TransCAD) 16.36 14.48 13.78 11.38 14.41 15.44 19.64 18.79 17.95 22.17 41.04 18.68 23.70 n/a n/a n/a n/a n/a n/a
n/a n/a
n/a n/a
2000 CTPP (Catoosa)
21.20 n/a n/a n/a n/a n/a n/a
2000 CTPP (Hamilton)
n/a n/a
26.50 n/a n/a n/a n/a n/a n/a
2000 CTPP (Walker) 2000 6
14.37
TDOT Target*1
8.50
Nashville Knoxville * 19.26 12.05 n/a 6.82 n/a n/a n/a n/a 11.48 7.98 12.36 7.14
2002
2007 2000 Chattanooga 2007 (TransCAD) Chattanooga 2000 (TransCAD) Two-Digit Two-Digit Intrazonal Intrazonal Total Trips Trips % Intrazonal Total Trips Trips % Intrazonal 0 #DIV/0! 14,931 7.04% 0 212,113 0 #DIV/0! 9,459 11.12% 85,068 0 0 #DIV/0! 15,828 9.93% 0 159,420 0 #DIV/0! 19,585 21.08% 92,919 0 0 #DIV/0! 32,266 11.16% 0 289,013 0 #DIV/0! 34,853 8.02% 0 434,513 0 #DIV/0! 4,995 3.06% 163,330 0 0 #DIV/0! 120,286 3,550 2.95% 0 0 #DIV/0! 31,580 1,309 4.15% 0 0 #DIV/0! 11,464 136 1.19% 0 0 #DIV/0! 131,917 9.18% 0 1,436,376
2007 Chattanooga (TransCAD) 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
Average Trip Length (in Minutes)
Trip Distribution
2000
2001 7
3-5%
1-4% 10-12% 3-9% 4-10% 3-7% 5-9%
New FDOT Guidelines*2
14.36
FHWA Target*3
27.80 19.80
19.95 16.58
Memphis Montgomery Savannah * 19.00 19.90 19.80 n/a n/a n/a 12.30 n/a 15.10 13.90 n/a n/a 13.40 17.40 15.40 13.20 16.70 13.40 17.20 15.80
2004
TDOT Target*1
26-58 n/a
12-35 n/a 9-19 11-19 8-20 6-19 n/a
New FDOT Guidelines*2
n/a n/a
8.1-17.1 n/a
10.4-17.3
11.2-35.4 8.9-15.9 8.6-18.7
FHWA Target*3
0 0 0 0 0 0 0 0 0 0
1 2 3 4 5 6 7 8 9 10
1 2 3 4 5 6 7
1 2 3 4 5 6 7 8
CBD CBD Fringe Residential OBD Rural Urban Undeveloped Mountainous 1 2 3 4 5
Interstate Expressway Principal Arterial Divided Principal Arterial Undivided Minor Arterial Collector Ramp One-Way
0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
1.00
21%
11
5-20% * 21%
22%
25%
60% 47% 36% 29%
2
* FHWA Target: R more than 0.88
3
* New FDOT Target: N/A
2
Coefficient of Determination R (Correlation Coefficient of Actual Counts and Model Volumes) 1 2 * TDOT Target: R more than 0.88
2
0.00%
>50,000
15-25% *
10
10
20-30% *
22%
25%
0.00%
0.00%
25,000 - 50,000
25-50%
60% 47% 36% 29%
0.00% 0.00% 0.00% 0.00%
65
25.01 - 35.00 35.01 - 45.00 45.01 - 55.00 55.01 - 65.00 > 65
County Boundary
MPO Boundary
Water Bodies
2007 Model Network
< 15 15.01 - 25.00
Southbound and Westbound Direction < 15
Northbound and Eastbound Direction
AM CMP Routes
.83
39.7 2/3 6
Inset 1
Inset 1
2
1
0
2
4
6 Miles
K
County Boundary
MPO Boundary
Water Bodies
> 65.00
55.01 - 65.00
45.01 - 55.00
35.01 - 45.00
25.01 - 35.00
15.01 - 25.00
< 15.00
Congested Speed (MPH)
2007 Model Network
24
153
153
153
24
75
75
2
1
Enterprise South
27
Chat tanooga Airport Hamilton Place
Northgate Mall
27
National Military Park
Inset 1
27
2007 Transcad Model Daily Congested Speeds
Inset 1
0
75
2
75
4
6 Miles
136,524
7.38% 72.85% 19.82% 7.33% 205,036 11.08% 34,391 1.86% #DIV/0! #DIV/0! #DIV/0! #DIV/0! 100.00% 1,849,845
99,457 27,060 10,007
Productions % by Productions 244,728 13.23% 98,303 5.31% 188,092 10.17% 115,148 6.22% 334,833 18.10% 492,790 26.64%
Year 2007 2000 2000
Person Trips / Household Region Chattanooga (TransCAD) Chattanooga (TransCAD) Chattanooga (MINUTP)
*2 FHWA Target
*2 New FDOT Guidelines
*1 TDOT Target
2.38 9.00 3.78 1.12 0.51 425,666 178,905 218,612
Persons per Household Internal Trips per Household Internal Trips per Person HBW Trips per Employee Employees per Person Total Population Total Households Total Employment
n/a
8.00 to 10.00
Person Trip/HH 9.00 9.44 7.44 8.50 to 10.50
2.50 9.44 3.78 0.74 0.73 395,061 158,055 287,918
2007 2000 Chattanooga (TransCAD)
Unit of Measure
Aggregate Trip Rates & Socioeconomic Summaries
Commercial Vehicles Light-Truck Medium-Truck Heavy-Truck Internal-External External-External SOV HOV Light-Truck Heavy-Truck TOTAL
Home-Based Work Home-Based School Home-Based Shop Home-Based Socrec. Home-Based Other Non Home-Based
Purpose
2007 Chattanooga 2007 (TransCAD)
Comparison of Total Trips by Purpose
Trip Generation
Productions % by Productions 212,113 12.72% 85,068 5.10% 159,420 9.56% 92,919 5.57% 289,013 17.33% 434,513 26.06%
2000 Chattanooga (TransCAD)
2002 Nashville 2.56 8.59 3.36 0.99 0.69 1,206,665 471,298 833,862
Memphis 2.65 8.20 3.09 1.71 0.51 1,103,539 416,830 533,378
2004
2000 Montgomery*5 2.68 8.64 3.23 0.75 0.66 299,180 111,793 196,799
163,330 9.80% 120,286 73.65% 31,580 19.34% 11,464 7.02% 237,104 230,906 13.85% 30,025 0.00% 0.00% 0.00% 0.00% 1,592,105 1,667,282 100.00%
99,435 27,064 10,010
136,524
Attractions 111,374 160,925 124,929 74,855 223,357 523,037
Unbalanced
2004
2000
2000
Savannah 2.53 7.66 3.03 1.42 0.55 232,011 91,834 127,000
2001
New FDOT Guidelines*2 2.0-2.7 8.0-10.0 3.3-4.0 n/a n/a
TDOT
8.06% 1.19%
Target*1 n/a 8.5-10.5 n/a n/a n/a
100.00%
100.00%
100.00%
13.00% 3.00%
Knoxville 2.45 8.40 3.43 5.70 0.60 761,346 310,412 457,796
2000
Memphis Montgomery Knoxville 25.15% 16.00% 13.09% 11.02% 8.16% 7.17% 39.00% 7.67% 28.10% 37.72% 31.78% 18.00% 20.89% 11.00%
8.82%
26.42% 8.79%
39.18%
Nashville 16.79%
2004
Target*3 n/a 8.0-14.0 3.5-4.0 n/a n/a
FHWA
22-31%
18-27% 47-54%
Target *1
9/27/2009 As for Run 21a but a few outstanding 2007 SE issues fixed after consulation with Yuen. Some very short network link area types and number of lanes also fixed.
Chattanooga 2007 MODEL VALIDATION SUMMARY
Run# 23 DATE: Description:
New FDOT
20-33% *4
Guidelines*2 12-24% 5-8% 10-20% 9-12% 14-28%
FHWA Target *3
2874671
231569 34278
1084215 913665
376294 234650
Run# 23
TEMPLATE 9/27/2009
2000 CTPP (Walker) 2002
2000
14.37
Purpose p
Smaller percentage of HBW intrazonal trips due to smaller zone sizes (zone splits)
n/a n/a
Comments:
n/a n/a
n/a n/a
26.50 n/a n/a n/a n/a n/a n/a
Home-Based Work Home-Based School Home-Based Shop Home-Based Socrec. Home-Based Other Non Home-Based Commercial Vehicles Light-Truck Medium-Truck Heavy-Truck TOTAL
23.70 n/a n/a n/a n/a n/a n/a
21.20 n/a n/a n/a n/a n/a n/a
6
TDOT Target*1
8.50
Nashville Knoxville * 19.26 12.05 n/a 6.82 n/a n/a n/a n/a 11.48 7.98 12.36 7.14
2007 2000 Chattanooga 2007 (TransCAD) Chattanooga 2000 (TransCAD) Two-Digit Two-Digit Intrazonal Intrazonal Total Trips Trips % Intrazonal Total Trips Trips % Intrazonal 4,730 1.93% 14,931 7.04% 244,728 212,113 6,517 6.63% 9,459 11.12% 98,303 85,068 23,534 12.51% 15,828 9.93% 188,092 159,420 13,795 11.98% 19,585 21.08% 115,148 92,919 43,379 12.96% 32,266 11.16% 334,833 289,013 47,349 9.61% 34,853 8.02% 492,790 434,513 3,786 2.77% 4,995 3.06% 136,524 163,330 2,723 2.74% 3,550 2.95% 99,457 120,286 936 3.46% 1,309 4.15% 27,060 31,580 127 1.27% 136 1.19% 10,007 11,464 143,090 8.89% 131,917 9.18% 1,610,418 1,436,376
Intrazonal Travel
Purpose
CTPP trip lengths longer since they were based on peak period and TransCAD model is daily
2000 CTPP (Catoosa)
Comments:
2000 CTPP (Hamilton)
Home-Based Work Home-Based School Home-Based Shop Home-Based Socrec. Home-Based Other Non Home-Based Commercial Vehicles Light-Truck Medium-Truck Heavy-Truck Internal-External TOTAL
2000 Chattanooga (TransCAD) 16.36 14.48 13.78 11.38 14.41 15.44 19.64 18.79 17.95 22.17 41.04 18.68
2007 Chattanooga (TransCAD) 18.26 13.85 12.84 13.55 12.44 14.18 17.88 17.78 17.20 20.75 37.38 14.53
Average Trip Length (in Minutes)
Trip Distribution
DATE:
2000
2001 7
3-5%
1-4% 10-12% 3-9% 4-10% 3-7% 5-9%
New FDOT Guidelines*2
14.36
FHWA Target*3
27.80 19.80
19.95 16.58
Memphis Montgomery Savannah * 19.00 19.90 19.80 n/a n/a n/a 12.30 n/a 15.10 13.90 n/a n/a 13.40 17.40 15.40 13.20 16.70 13.40 17.20 15.80
2004
Page 2 of 4
TDOT Target*1
26-58 n/a
12-35 n/a 9-19 11-19 8-20 6-19 n/a
New FDOT Guidelines*2
n/a n/a
8.1-17.1 n/a
10.4-17.3
11.2-35.4 8.9-15.9 8.6-18.7
FHWA Target*3
TEMPLATE 9/27/2009
345,072 200,101 58,310 157,697 161,845 186,882 86,810 79,891 335,995 298,244
1 2 3 4 5 6 7 8 9 10
1 2 3 4 5 6 7 8
1 2 3 4 5 6 7 8
CBD CBD Fringe Residential OBD Rural Urban Undeveloped Mountainous Industrial 1 2 3 4 5 -31% -3% -8% -5% 7% 4% 9% -10% 10% -12% -1% -2% 3% -4%
0.69 0.97 0.92 0.95 1.07 1.04 1.09 0 90 0.90 0.88 0.99 0.98 1.03 0.96
Chattanooga 2007 Volumes Over % Difference Counts Interstate 1.02 2% 1.04 Expressway 4% 0.98 Principal Arterial Divided -2% 0.86 Principal Arterial Undivided -14% 0.80 Minor Arterial -20% 0.98 Collector -2% 0.99 Ramp -1% 0.49 One-Way -51%
Chattanooga 2007 Total Count Vol/Count Ratio 343,472 1.00 198,576 1.01 67,059 0.88 158,856 0.99 198,514 0.82 202,070 0.93 79,242 1.10 87,602 0.91 316,594 1.06 298,668 1.00
-5.90%
>50,000
21%
22%
10
5-20% *
11
15-25% *
2
2
* FHWA Target: R more than 0.88
3
* New FDOT Target: N/A
1 Central City Partial Cordon 2 Tennessee River Crossing 3 North-South Downtown 4 East-West Downtown 5 Missionary Ridge 6 South Chickamauga Creek 7 North-South North Hamilton Co. 8 Ringgold 9 TN/GA State Line 10 External Cordon Line
Page 3 of 4
21%
22%
25%
FHWA Target *3 60% 47% 36% 29%
-6.8 -1.6 -5.3 -7.8 -4.7
0.93 0.98 0.95 0.92 0.95
0
10000
20000
30000
40000
50000
60000
70000
-11.8 -8.2 -4.0 -8.4 9.7 1.9 -5.0
0.88 0.92 0.96 0.92 1.10 1.02 0.95
0
10000
TDOT 2000 Volumes Over % Difference Counts Accuracy Level *1 0.98 +/- 7% -1.6 0.94 +/- 7% -5.6 0.98 +/- 10% -2.1 0.94 +/- 10% -6.1 0.88 +/- 15% -12 0.98 +/- 25% -2.2 n/a 0.71 n/a -29.1
2000 Vol/Count Ratio 0.97 0.94 0.97 0.91 0.90 0.99 1.09 1.06 1.02 1.00
Coefficient of Determination R 2 (Correlation Coefficient of Actual Counts and Model Volumes) 2 0.95 *1 TDOT Target: R 2 more than 0.88 R
1.50%
25,000 - 50,000
Percent Difference for Daily Volumes (calculated for Links with Counts) TDOT New FDOT Chattanooga 2007 AADT TransCAD Target *1 *9 Guidelines *2 48.90% 60%
