A Dynamic Programming Approach for Optimal Signal Priority Control Upon Multiple High-Frequency Bus Requests

This article presents a priority signal control model for multiple bus requests. The proposed model aims to generate the optimal priority serving sequence to maximize the utilization of available green times by buses, but not to incur excessive congestion for other vehicular traffic. This study first depicts the serving sequence for multiple priority requests as a multistage decision process and explicitly models three bus priority strategies under the constraints of minimum green time, acceptable degree of saturation, and length of priority window. Further, it formulates a dynamic programming model to optimize the serving sequence for multiple priority requests as well as the corresponding signal timing plans under various levels of bus occupancy, schedule deviation, and traffic demand. A rolling time horizon approach is employed to solve the proposed model in real time. Comparative analysis results have shown that the proposed dynamic programming model outperforms the first-come-first-serve policy in terms of reducing bus delays, improving schedule adherence, and minimizing the impacts on other vehicular traffic. Computational performance analysis has further demonstrated the potential of the proposed model and algorithm to be applied in real-time bus priority control system.