The effects of pre-signals at an isolated intersection: Simulation results

Abstract

A pre-signal is an additional signal upstream of the main signal which can be used to provide bus priority. Its primary purpose is to allow buses to jump the car queues at the intersection while cars can still use all lanes at the main signal to fully utilize the capacity of the intersection. In this way, bus delay at the intersection is reduced without causing extra stress to the overall traffic. The effects of the pre-signals at an isolated intersection have been analytically studied and compared to empirical measurement. However, on the arterial and network level, it is very difficult to study the effects analytically and from our best knowledge there does not exist real work examples. Therefore a simulation model is needed. The goal of this research is to validate the simulation approach by showing that at the isolated intersection level a VISSIM simulation model calibrated with the collected empirical data produces similar results. Therefore, it can be used to understand the mechanism behind the operation of pre-signals and can provide direct visual insights into its effects on traffic flow. With the developed micro-simulation, the effects of the red time duration at the presence of buses could be examined. Recommendations could then be given regarding how long this red signal should be when implementing pre-signals.