An integrated energy-efficient and transfer-accessible model for the last train timetabling problem

Subway is considered to be one of the most energy-intensive transportation modes for its high operating frequency. However, energy-efficient operations for the subway system are of great importance yet have not been paid much attention to. In this study, we first develop an integrated energy-efficient and transfer-accessible model to minimize the tractive energy consumption and maximize the number of last train connections, which could contribute to the development of high energy-efficient strategies and the construction of wide-accessibility timetables for the subway system. Four tractive modes, which are accelerating–braking (A–B) mode, accelerating–coasting–braking (A–Co–B) mode, accelerating–cruising–braking (A–Cr–B)​ mode, and the mixed mode, are proposed to facilitate the last train operations. A real-life case study of the Beijing subway network is solved by a tailored genetic algorithm. Results show that the A–B mode is the most energy-intensive with an energy consumption of 466.9 kWh, while the A–Co–B mode becomes the most energy-efficient (402.5 kWh). The A–Cr–B and the mixed modes consume 442.2 kWh and 412.8 kWh, respectively. The findings are of significant value for subway companies in addition to their academic merits.