Development of a Dynamic Transit Signal Priority Strategy

Transit Signal Priority (TSP) is a popular strategy used to enhance the performance of transit systems by modifying the signal control logic to give transit vehicles priority at signalized intersections. Conventional TSP strategies used in most cities have been shown to offer significant benefits in reducing the delays of transit vehicles. However, there have been concerns about some shortcomings of conventional TSP strategies which limited their applications. The main concern is the potential negative impact on cross street traffic. Another concern is the static nature of conventional TSP strategies and the lack of responsiveness to real-time traffic and transit conditions. This paper describes the development and evaluation of a dynamic TSP control system which has the ability to provide signal priority in response to real-time traffic and transit conditions. The dynamic TSP system consists of three main components: a virtual detection system, a dynamic arrival prediction model, and a dynamic TSP algorithm. Two case studies are presented to test and compare the dynamic and the conventional TSP systems. In the first case study, a hypothetical intersection is simulated, while the second case study involves simulating a proposed Light Rail Transit (LRT) line. For both case studies, a virtual detection system was developed in VISSIM, along with a linear travel time arrival prediction model. Finally, a dynamic TSP algorithm was developed to determine what TSP strategy to use and when to apply it. The results showed that the dynamic TSP system reduced the total delay of transit vehicles and outperformed the conventional TSP system in terms of reducing the transit trip travel time.