A subway timetable optimization model for maximizing the utilization of recovery energy

Since the regenerative braking technique can recover considerable electricity from braking trains, it is maturely applied in subway systems. Generally speaking, except a small part of the recovery energy is used by the on-board auxiliary services, most of them is fed back into the overhead contact line. If the feedback energy cannot be absorbed by adjacent accelerating trains timely, it will be consumed by resistances. For maximizing the utilization of recovery energy, this paper proposes a timetable optimization model to coordinate the accelerating and braking processes of up trains and down trains. Firstly, we analyze the coordinating rules. Secondly, we propose an integer programming model to maximize the utilization of recovery energy with headway time and dwell time control. Furthermore, we design a genetic algorithm to solve the optimal timetable. Finally, we conduct numerical examples based on the operation data from Beijing Yizhuang subway line of China. The results illustrate that the proposed model can significantly save energy by 21.58% compared with the current timetable.