Optimization of Cross-Line Train Operation Scheme for Passenger Flow Corridors in Urban Rail Transit

Urban rail transit passenger flow corridor connect core urban areas with key functional zones across different urban spatial layers, representing concentrated areas of urban spatial resources and economic activities.Their transportation efficiency significantly impacts both the capacity of the rail transit network and socio-economic activities. Focusing on these corridors, this study adopts a" trunk line with multiple branches" topological structure to develop a multi-objective nonlinear optimization model that minimizes enterprise operational costs, passenger travel costs, and load factor imbalance. The model uses train frequency and marshaling plans as decision variables as decision variables, solved via an NSGA-Ⅱ algorithm. Using Beijing's Huilongguan/Tiantongyuan-Zhongguancun corridor as a case study, the model demonstrates effective accommodation of multi-directional travel demand between residential and employment hubs. To evaluate optimization performance, an improved distance-based optimal solution selection method identifies a solution with 2 639.17 h (passenger travel time), 103 716.24 yuan (operational cost), and 0.086 (load factor imbalance). Compared to isolated line operation schemes, this achieves 14.09%reduction in passenger travel time and 43.01% lower load factor imbalance, with a 17.22% increase in operational costs. At the same time, in complex line networks, the restrictions of the maximum carrying capacity of the main line section and the minimum service level of the branch section have a great impact on the effect of the optimization scheme. By increasing the upper limit of the main line capacity, the study investigates the impact of capacity restrictions on the optimization of train operation schemes in passenger flow corridors. The results show that under the condition of improving the line carrying capacity, the diversity of Pareto solutions increases, passenger travel time is significantly reduced, and the balance of service is improved. These findings provide empirical guidance for cross-line operation planning and practical rail transit management.