Two-Layer Optimization Based Timetable Rescheduling in Speed Restriction for High Speed Railway

A mixed integer linear programming (MILP) based two-layer optimization model is proposed within a simulation framework to handle timetable rescheduling in high speed railway during speed restriction period. The capacity of high speed line may become deficient when speed is restricted. To avoid extensive delay, four common rerouting actions are discussed, including merging trains, canceling trains, making detour to existing railway lines and advancing trains' departure time. In the proposed two-layer rescheduling model, the top-layer (rerouting) objective is to make an optimal rerouting plan with selected rerouting actions. Given a specific rerouting plan, the second layer (time adjustment) of the rescheduling model focuses on minimizing the total delay as well as the number of seriously impacted trains. In addition, two peripheral modules are designed for facilitating the interaction with dispatchers, who may iteratively invoke the rescheduling model with different settings. One is a line capacity evaluation module executed before rescheduling, which is innovatively used to generate constraints for the rerouting optimization. The other one is a decision tree based result assessment module. It is used at the end of each execution of the rescheduling model to determine if the result is acceptable. The proposed rescheduling model is simulated on the busiest part of a high speed railway line in China. The entire case study shows the significance of rerouting in case of speed restriction. The results shed light on how we could better use line capacity in case of speed restriction, so that passengers can be satisfied and cost can be reduced as much as possible.