关键词: 城市交通, 客货共运, 混合整数线性规划, 列车运行图, 车底周转计划

Abstract: The passenger demand of an urban rail transit line is relatively small, and the departure interval is large during off peak hours. Using the spare capacity of rail transit lines to transport freight can improve line utilization and bring economic benefits. Without adjusting passenger train service planning, this paper uses passenger and special freight trains to transport freights simultaneously. The study optimizes the bilateral freight train timetable and shipment allocation while considers rolling stock utilization. A collaborative optimization model is developed with the objective of maximizing the net freight profit to determine train stopping plans, train formation, schedules, rolling stock circulation plans, shipment allocation, and freight storage capacity to be reserved at stations. The proposed method considers the constraints of train operation safety, rolling stock circulation plan, freight transportation time requirements, and so on. The model is transformed into a mixed-integer linear programming model by the linearization method and then is solved by Gurobi software. The case analysis shows that compared to the step-by-step optimization model that optimizes train service planning and shipment allocation before the rolling stock circulation plan, the proposed method can reduce the number of rolling stocks in operation by 3, reduce the operating cost of freight trains by about 23.6% , and increase the net freight profit by 10.3% . The sensitivity analysis indicates that compared with passenger trains, improving the freight space and loading/unloading efficiency of the freight trains can increase net freight profit more effectively.

Key words: urban traffic, mixed transport of passenger and freight, mixed-integer linear programming, train timetable, rolling stock circulation plan