Integrated optimization of train services plan and passenger flow control on an oversaturated suburban metro line

Suburban metro lines play an important role in daily commuting, which transport passengers from suburban areas to the city center in the morning peak. However, the excessive commuting demand leads to oversaturation on trains and platforms, especially at the stations near the city center. To ease the oversaturation of suburban metro lines, an integrated optimization on inbound passenger control and train service planning including short-turn and non-periodic services has been proposed. The proposed approach aims to reduce the maximum number of stranded passengers at the platforms while the total number of waiting passengers outside stations and the running kilometers of all train services are also minimized. To ensure the feasibility of solutions, the train connections and available rolling stock fleet size have been formulated. A genetic algorithm embedded with brute force is adopted to efficiently solve the proposed large-scale nonlinear model. Finally, a real case of Beijing subway Fangshan line shows that the inbound passenger control and short-turn services help to evidently reduce the stranded passengers at the stations near the city center. Compared with the practical train services without inbound passenger control and the integrated model without short-turn services, the integrated model is able to improve the sum of three objectives by more than 14.8%.