A Dynamic Model for Adaptive Bus Signal Priority

The adaptive traffic signal control system, as well as the Transit Signal Priority (TSP) concept has both been viewed as important opportunities for reducing overall traffic congestions and improving bus transit services. However, few studies were conducted on combining them together. A dynamic signal timing optimization model was developed in this research, which aims at reallocating green times among the phases with considering the realtime traffic flow condition and the bus priority request. In the model, both arrival and departure flows are described by time-dependent functions, the arrival of a bus with priority request is represented by giving a weight factor to the traffic demand of the associated approach. The weight factor is also defined as a time-dependent function of three variables: present traffic demand and queuing conditions of the bus arriving approach vs. that of the intersection and the lateness of the target bus. As the bus is converted to a relevant number of arrivals of passenger vehicles by the weight factor, the objective of the dynamic model is to minimize the average delay at the intersection.