Traffic Signal Optimization with Application of Transit Signal Priority to an Isolated Intersection

Transit signal priority (TSP) is a control strategy that has been used extensively to improve transit operations in urban networks. However, several issues related to TSP deployment—including the effect of TSP on auto traffic and the provision of priority to transit vehicles traveling in conflicting directions at traffic signals—have not yet been addressed satisfactorily by existing control systems. This paper presents a real-time, traffic-responsive signal control system for signal priority on conflicting transit routes that also minimizes the negative effects on auto traffic. The proposed system determines the signal settings that minimize the total person delay in the network while assigning priority to the transit vehicles on the basis of their passenger occupancy. The system was tested through simulation at a complex signalized intersection located in Athens, Greece, that had heavy traffic demands and multiple bus lines traveling in conflicting directions. Results showed that the proposed system led to significant reductions in transit users’ delay and the total person delay at the intersection.