A Passive Transit Signal Priority Approach for Bus Rapid Transit System

The objective of Bus Signal Priority (BSP) for Bus Rapid Transit System(BRT) is not only decreasing buses delay but also enhancing the reliability of bus service by keeping buses on schedule or maintaining bus headway adherence. One problem with existing bus priority strategies is that they do not care about the variances of sequential buses delay at intersections. Usually buses arrive at intersection at defined frequency and leave it at dramatically fluctuating headways because the signal statuses when each bus arrives at the intersection and delay for each bus are different. For BRT system, the travel time reliability of buses on links is improved dramatically, traffic signal control system may be the main sources to induce bus headway fluctuation and schedule deviation. This paper mathematically depicted the relationship between the departure frequency of a BRT bus line, cycle length of signalized intersection and number of Different Signal Status (DSS) when buses arrive at the intersection. The optimal number of DSS, which was found to be ONE, was obtained by analyzing their effects on the bus average delay and deviation of headways. This paper also presented a bus signal priority control strategies for different numbers of DSS. An intersection with an exclusive Bus Rapid Transit (BRT) lane, Wuyingshan-Beiyuan intersection, was adopted to test the proposed model. The results of high performance simulation software VISSIM validate that there are close relationships between bus frequency, signal cycle, number of DSS, bus headway deviation and bus delay. The proposed signal priority strategies can decrease average bus delay and bus headway deviation dramatically without significantly impacting motor vehicles delay.