Unsignalised Junction Capacity

1. INTRODUCTION Capacity is the ability of a junction or roadway to accommodate traffic. It is important to be analyzed to estimate the maximum amount of traffic that can be accommodated by a roadway or junction while maintaining its quality. This can be determined by finding the Level of Service (LOS). Level of service (LOS) uses qualitative measures that characterized both operational condition within a traffic stream and motorists’ and passengers’ perception of them. The concept of LOS at unsignalised intersections is the resulting stopped delay per vehicle which gives indications of driver frustration, discomfort, lost travel time and fuel consumption. 2. OBJECTIVE The objective of the experiment is: i.

To determine the capacity and the LOS for the unsignalised interception

3. LEARNING OUTCOME At the end of the laboratory session, student should be able: i Known how to operate with SIDRA INTERSECTION application. ii Analyses how to interpret the output of the study. iii Work in a group to produce the relevant technical report. iv 4. THEORETICAL BACKGROUND

5. PROBLEM STATEMENT

Traffic can operate smoothly when the rate of flow is less than at capacity, but excessive delay and congestion can occur when the rate of flow is at or near capacity. In planning and design of highway facilities, the principal purpose is to design or plan facilities that will operate at flow rates below their optimum rates. However, this objective can be achieved only if a good estimate of the optimum flow of a facility can be made. Inefficient junction operations can cause severe traffic congestion, thus affecting the surrounding environment. There are several factors that need to be considered including the safety of road users and adequacy of road infrastructure. Long-standing traffic woes received very little attention despite the huge investment that has been spent in developing and enhancing expertise in traffic and transportation engineering. In this road traffic study, three (3) problems need to be tackled in order to solve traffic congestion, safety and related environmental issues such as: i Ensure the safety issues for road user. ii Evaluate the junction performance. iii Use an appropriate software to verify the field works result. 6. PROCEDURE

7. ANALYSIS DATA (MASUKKAN YANG PRINTSCREEN)

8. DISCUSSION

As we have conducted both site observation and software calculation, we compare the result of Level of Service (LOS) from both activities. From the site observation, after we get the volume per hour we calculated the conflicting flow (Vc), critical gap, Tc (Table 4.3) and potential capacity, Cp (Figure 4.2) and actual capacity (Cm). This calculation is only applicable for the delay movement. We also calculated the shared-lane capacity before we get the Level of Service (LOS) of each movement. Then, we inserted our junction layout and all the data into the SIDRA software. SIDRA stands for Signalised/Unsignalised Intersection Design and Research aid where it can be used to determine the Level of Serviceability (LOS), network capacity and performance analysis of an intersection. SIDRA Intersection is more convenient software used for LOS determination of an intersection (at the critical points) which has a large number of traffic volume compared to manual calculation obtained from Arahan Teknik Jalan. RESERVE CAPACITY (PCPH)

LOS

EXPECTED DELAY TO MINOR ROAD TRAFFIC

400

A

Little or No Delay

300-399

B

Short Traffic Delays

200-299

C

Average Traffic Delays

100-199

D

Long Traffic Delays

0-99

E

Very Long Traffic Delays

*

F Table 3.0 LOS Criteria for Unsignalized Intersections

(Adopted from A Guide to the Design of At-Grade Intersections in Arahan Teknik (Jalan) 11/87, Kuala Lumpur: Jabatan Kerja Raya Malaysia)

From SIDRA analysis, the LOS at lane 1, 2 and 5 is tabulated below:

Lane

Level of Service

Expected Delay to Minor Road Traffic

1

A

Little or No Delay

2

A

Little or No Delay

5

A

Little or No Delay

In the previous junction capacity laboratory, the LOS of lane 2, 5 and 6 is calculated manually using The Guide to the Design of At-Grade Intersections in Arahan Teknik (Jalan) and the result is shown as below : Lane

Reserved Capacity

LOS

1

417.5

A

2

421.5

A

5

793.5

A

Summary of the results obtained between calculation according to the guide and SIDRA Intersection is as below: Lane

SIDRA Intersection Software

A Guide to the Design of AtGrade Intersections in Arahan Teknik (Jalan)

1

A

A

2

A

A

5

A

A

Based on the summary, it is known that the LOS obtained from the calculation using the guide is the same as SIDRA Intersection software.

9. CONCLUSION

From the discussion, we can conclude that the junction capacity study is important to evaluate existing traffic conditions and highway systems deficiencies so we can proposed the changes on capacity and traffic condition/ The level of Service (LOS) at the selected junction is categorized as Category A because it has little or no delay. This can be observed from the site observation and also the software calculation. Therefore, any improvement is not required for the time being because the road is in a good condition and won’t create problems for the users.