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Estimation of Operation Capacity on the Exclusive Median Bus Lane

Wonho KimㆍSeungjun KimㆍTaejung Kim


Since the first introduction of the exclusive median bus lane (EMBL) in 1996, it has been continuously expanded to 120km on 12 arterial roads. In addition to the urban railway, it plays a role as the backbone of public transportation in Seoul and is responsible for a large part of the demand for wide-area transportation. However, continuous urbanization and construction of satellite cities require the addition of broad-area bus lines, causing traffic congestion in some sections in the EMBL. The urban sprawl will continue in the future and it is expected that the bottleneck will be extended to all EMBLs. Therefore, in order to recover the inherent functions of the EMBL, it is necessary to improve the operation in addition to the physical improvement.

The improvement of EMBL management and operation requires estimation of the operating capacity. The existing capacity estimation method, which is used as a design guideline for the EMBL, has a limitation that it can not consider the level of congestion and passenger service levels because the capacity obtained from the existing method is the maximum throughput of buses during a given time. It is necessary to estimate the maximum operating capacity that provides the level of service which the passengers can tolerate. The estimation method should be able to reflect the characteristics of the EMBL in Seoul, which is different from that in foreign countries. The capacity estimation method proposed in this study considers the user's required service level while maintaining the function as the EMBL.

The bus arrival distribution at the bus stop for the EMBL is determined by the traffic signal at the upstream intersection. Buses that pass through the stop line during green signal time arrive at a bus stop in a platoon and depart from the bus stop before the next bus platoon arrives. The concept of signal failure at the signalized intersection is introduced to define a service failure (S.F.) situation where none of the buses can complete the service at a bus stop during one signal cycle. The methodology and results are presented below.

Through the field survey and bus management system (BMS) data on most congested bus stops, bus behaviors, the number of bus arrivals, and bus queue lengths were investigated when S.F. occurred. The results of the investigation were utilized to estimate the maximum operating capacity for each stop so that S.F. does not occur. The suggested operating capacity was estimated to be about 30% lower than that with the existing estimation method. On comparing the results of the existing estimation method with those collected from the field, it is analyzed that the existing method tends to overestimate the maximum operating capacity. The capacity presented in this study is the capacity that can be tolerated from the viewpoint of the user rather than the operator.

The demand for the EMBL is expected to increase further due to the increase in the demand for wide-area transportation in the future. Therefore, there is an urgent need to establish an operating system that includes monitoring of the main function of the EMBL and the maintenance of the appropriate service level, and it is expected that the results presented in this study will be used as the basic data for establishing the management plan.




01 Major Causes for Congestion on EMBL

1_Traffic Congestion on EMBL

2_Development of DB for Operational Analysis

3_Major Influence Factors for Bus Travel Time

4_Congestion Mitigation Measure


02 Estimation Methods of Capacity on EMBL

1_Review of Conventional Estimation Methods

2_Needs for Estimation Method based on Bus Queue Length


03 Estimation of Maximum Operating Capacity

1_Development of Estimation Method for Operating Capacity

2_Estimation of Maximum Operating Capacity


04 Closing Remarks