Integrated Optimizing Train Operational Plan For Urban Rail Transit Considering The Space–time Dependent Passenger Demand

Prioritizing the development of public transportation systems such as urban rail transit can help reduce urban traffic congestion and improve the quality of travel for residents.With the rapid development of urban rail transit systems in China’s megacities,the growth of passenger demand is accompanied by uneven distribution over operation period and urban rail networks.The optimization of train operational plan can improve the passenger service and resource utilization efficiency in the urban rail system.Most of the existing studies independently optimize sub-problems in urban rail operation,such as train frequency setting,scheduling,and rolling stock circulation planning,which may lead the urban rail system to be operated in a suboptimal way.This study focuses on the uneven distribution of passenger demand in time and space,then optimizing the train operational plan for urban rail transit in an integrated way.Given time-dependent origin-destination(OD)passenger demand and the related facility and equipment parameters,the integrated urban rail train operational plan optimization problem can be defined as follows: considering passengers’ path choice,under the constraints of train running,turnaround and rolling stock circulation,determining the number of train services,departure and arrival times in schedule and rolling stock schedule,so that the passenger travel costs and urban rail operation costs are minimized.With considering multiobjectives,short-turning strategy and modular vehicles,this study proposed three integrated urban rail train operational plan optimization models,and provides decision support for railway companies in their daily operation and management.The main content of this study includes following four aspects:(1)Proposed a schedule-based passenger assignment method for urban rail systems.The space-time travel network is designed based on the schedule and time-dependent O-D demand,and proposed an equilibrium assignment model for urban rail with tight train capacity constraints.The sensitivity analysis is performed to capture the impacts of demand intensities on the outputs.It further shows that the proposed model can be used to obtain key indicators such as passenger travel costs and waiting time,making it possible to optimize the train operational plan based on passenger assignment.(2)Developed an integrated optimization model of urban rail train operational plan based on time-varying demand.The model considering passengers’ path choice,proposed systematic constraints of operational plan,finding the optimal number of train services,departure and arrival times in the schedule,and rolling stock schedule.An algorithm for largescale cases is proposed based on the Benders decomposition method.The case study shows the detail of optimal schedules and passenger service.Finally,the performance of the integrated optimization model is analyzed under different passenger demand intensity,train capacity and objective weights.(3)By introducing the short-turning strategy,a new integrated optimization model is proposed to address the uneven spatial distribution of passenger demand over the urban rail network,which incorporates decision on train path choice and related constraints at short-turning station.The model has good extensibility and can be further used to explore the optimization of train operational plan under different turning strategies.Besides,a variable neighborhood search algorithm is proposed for largescale cases.Comparative analysis shows that considering the short-turning strategy can better deal with the unbalanced spatial distribution of passenger demand on urban rail lines and reduce passenger travel costs.Meanwhile,it can also speed up the rolling stock circulation and improve the operational efficiency.(4)Incorporating modular trains in urban rail operation and train operational plan optimization.The new model simultaneously considers the modular trains and short-turning strategy.The comparison analysis indicates that the combination of two strategies can significantly improve the passenger service quality while reducing the operation cost.Furthermore,more flexible modular trains make the train operational plan more feasibility,which is beneficial to the improvement of passenger service and operation efficiency.The integrated optimization models of urban rail train operational planning in this study provides theoretical and decision support for the efficiency improvement of urban rail operation and organization.