A rule-based real-time traffic responsive signal control system with transit priority: Application to an isolated intersection

Previous experience has shown that real-time, traffic-responsive signal control has the ability to improve traffic operations in urban areas when compared to traditional fixed-time control. However, most of these experiences have focused primarily on the impact on private automobiles. This paper describes the development and evaluation of a fully distributed, real-time, traffic-responsive model named Signal Priority Procedure for Optimization in Real-Time that explicitly considers the impacts of transit vehicles. This model is unique in two ways. First, the model explicitly considers the interference caused to the general traffic by transit vehicles stopping in the right of way to board and discharge passengers. Second, when considering priority passage for transit vehicles, the potential effects that such preferential treatment might have on other traffic are explicitly quantified. This paper describes the structure of the model and demonstrates its capabilities on an isolated intersection for a range of traffic demands and with and without transit vehicles. The rule-based signal optimization procedure provided delay reductions for most of the traffic conditions examined when compared to both fixed-time and traffic actuated control. While the results reported in this paper are limited to an isolated intersection, the model is capable of being applied to a network of signals. Evaluation of its performance on a corridor has been conducted and will appear in the literature in the near future.