Study on Tram Travel-Time Reliability Characteristics for Optimal Traffic Signal Control

Abstract

This paper quantitatively investigates the effects of the number of intersections between adjacent stations $(N)$ and different periods on tram travel-time reliability to provide a decision basis for adopting optimal signal-control methods. Station spacing data, intersection information on the line, 10 day planned operation schedules, and actual operation data of Zhangjiang tram line 1 were collected. The tram travel-time distributions were analyzed under seven typical scenarios (i.e., N = 0, 1, 2, 3, off-peak hours, morning peak hours, and evening peak hours). The results showed that the lognormal distribution described the tram travel time better than did the normal and gamma distributions. It was demonstrated that scenarios $N=0$ , $N=1$ , and off-peak hours were of high reliability; morning peak hours and evening peak hours were of medium reliability; and scenarios $N=2$ and $N=3$ were of low reliability. The unreliability of travel time increased along with the increase of the mean and the fluctuation of travel time. An optimized signal-control strategy based on travel-time reliability was put forward and VISSIM simulation of an interval was conducted, verifying the effectiveness of the proposed strategy. The findings will help tram-management agencies to adopt suitable and flexible signal-control strategies according to the actual varying condition.