Signal Timing Optimization Models for Two-Stage Midblock Pedestrian Crossing.

Finding an appropriate signal timing plan is one of the most critical operational issues for signalized two-stage midblock crossing which has been increasingly installed in highly populated areas in developing countries such as China. In this paper, three signalization 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: cycle length optimization and offset optimization. The cycle length optimization is formulated as a mix integer linear programming problem to minimize the cycle length with constrains of the maximum acceptable saturation degree 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 for the offset of two-stage pedestrian signal is also formulated as a mix integer linear programming problem to provide maximum green bandwidth for two successive pedestrian crossings. A case study in Shanghai, China has been performed using VISSIM simulation to validate the proposed models. Results reveal that the proposed models are promising in determining the signalization type and optimizing the signal timings for two-stage midblock pedestrian crossings. Sensitivity analysis with respect to the system performance was also conducted to better assist traffic engineers in selecting appropriate signalization types and acceptable degrees of saturation. The analysis results from this study will offer the basis for traffic practitioners, researchers, and authorities to design and assess signal plans for two-stage midblock pedestrian crossings.