Saving Energy and Improving Service Quality: Bicriteria Train Scheduling in Urban Rail Transit Systems

This paper formulates a two-objective model to optimize the timetables of urban rail transit systems based on energy-saving strategies and service quality levels. With time-dependent passenger demands, the calculation process of passenger travel time simulates boarding and alighting activities with some constraints to guarantee traffic capacity and meet passenger requirements, particularly in the over saturated conditions. Traction and auxiliary energy consumption are considered in the operational energy consumption calculation. The regenerative energy, which is generated from braking trains and simultaneously used by traction trains, is also taken into account in the calculation with transmission loss. Through adjusting the headway, this model makes a tradeoff between passenger travel time and operational energy consumption with guaranteed traffic capability. Furthermore, a genetic algorithm with the binary encoding method is designed to obtain high-quality timetables. Based on the operational data of the Beijing Yizhuang subway line, we implement some numerical experiments to demonstrate the effectiveness of the proposed approaches.