Signal Timing Optimization Models for Two-Stage Midblock Pedestrian Crossing

Finding an optimal signal timing plan is one of the most critical operational issues for signalized two-stage midblock crossings, which are increasingly being installed in highly populated areas in developing countries, such as China. In this paper, three signalization control types (simultaneous, progressive, and separate signalization) for two-stage midblock pedestrian crossings are proposed. Both vehicular traffic and pedestrian movements are considered in a unified framework by solving two problems: the optimization of cycle length and the optimization of offsets. The cycle length optimization problem is formulated as a mixed-integer linear programming problem to minimize the cycle length with constraints of the maximum acceptable degree of saturation of vehicle movements, the minimum clearance time, the pedestrian green time, and the maximum number of pedestrians waiting on a central refuge island. The optimization problem of the offset of the two-stage pedestrian signal is also formulated as a mixed-integer linear programming problem to provide the maximum green bandwidth for two successive pedestrian crossings. A VISSIM simulation and a case study in Shanghai, China, were carried out to validate the proposed models. The proposed models are promising in determining the signalization control type and optimizing the signal timings of two-stage midblock pedestrian crossings. Analysis of the sensitivity of the performance of the system was also conducted to assist traffic engineers with selecting appropriate signalization control types and acceptable degrees of saturation. The results from this study offer a basis for traffic practitioners, researchers, and authorities to design and assess signal plans for two-stage midblock pedestrian crossings.