Timetable Optimization for a Two-Way Tram Line With an Active Signal Priority Strategy

Modern trams typically run along semi-exclusive right-of-way. Although tram lanes isolate trams from other traffic in the running sections, the operation process will be affected by signal control. To improve the service quality of trams and reduce the negative impact on intersections caused by bidirectional priority requests, we propose a timetable optimization method for a single two-way tram line based on active transit signal priority strategy. Combining with the characteristics of bidirectional signal priority strategy, trams can pass through the intersections without stopping by adjusting the running times and dwell times. A multiobjective optimization model of a tram timetable is established to minimize the total travel time, dwell time increment, and negative effect of the signal priority strategy. For obtaining a timetable with equal satisfaction for the three objectives, we adopt the fuzzy mathematical programming approach to transform the problems into mixed integer linear programming (MILP) problems, which can be solved by using standard solvers. The case study of Nanjing Qilin Tram Line 1 shows that the timetable optimization method designed in this paper can effectively improve the service efficiency of trams, and reduce the negative impact of the signal priority strategy on social vehicles. These empirical findings can give us some useful insights on the optimum design of tram timetable.