How to improve transportation capacity of oversaturated metro lines? A flexible operation approach with extra-long train compositions

Authors

Xiaopeng Tian
Lixing Yang

Document Type

Journal Article

Publication Date

2025

Subject Area

mode - subway/metro, operations - capacity, ridership - demand, planning - methods

Keywords

Metro, capacity, train composition lengths

Abstract

Under regular metro operation conditions, one critical bottleneck to improving metro transportation capacity is fixed-length train compositions. These fixed-length compositions are mandated to not exceed station platform lengths, thereby limiting the potential for increasing capacity to effectively accommodate oversaturated passenger demand. To this end, we focus on a flexible metro operating system equipped with extra-long train compositions, which allows trains to protrude beyond both ends of the station platforms for additional capacity. Driven by oversaturated and time-dependent passenger demand, we develop a compact integer linear programming model to determine train composition lengths and train-platform alignment relationships. When using commercial solvers to directly handle this model, complexity analyses and computational practice show that it is less efficient for large-scale experiments. We thus reformulate it as a column-based optimization model, while employing a column generation algorithm to solve its linear relaxation version and customizing a dynamic programming method to generate promising column variables. To achieve high-quality integer solutions, we carefully embed the column generation into a branch-and-bound procedure and elaborate some accelerating strategies through theoretical analyses. The approach is applied to several test instances defined by using hypothetical and real-world lines. The computational results demonstrate that the proposed approach can significantly reduce passenger waiting times and effectively handle large-scale problems.

Rights

Permission to publish the abstract has been given by Elsevier, copyright remains with them.

Comments

Transportation Research Part B Home Page:

http://www.sciencedirect.com/science/journal/01912615

Recommended Citation

Tian, X., & Yang, L. (2025). How to improve transportation capacity of oversaturated metro lines? A flexible operation approach with extra-long train compositions. Transportation Research Part B: Methodological, 195, 103188.