A Comparison of Optimization Methods for Solving the Depot Matching and Parking Problem

We consider the Train Unit Shunting Problem, an important planning problem for passenger railway operators. This problem entails assigning physical train units to scheduled train services in such a way that the resulting shunting yard operations are feasible. As such, it arises at every shunting yard in the railway network and involves matching train units to arriving and departing train services as well as assigning the selected matchings to appropriate shunting yard tracks. We present a comparison benchmark of multiple solution approaches for this problem. In particular, we have developed a Constraint Programming formulation, a Column Generation approach, and a randomized greedy heuristic. We compare and benchmark these approaches against slightly adjusted existing methods based on a a Mixed Integer Linear Program, and a Two-Stage heuristic. The benchmark contains multiple real-life instances provided by the Danish State Railways (DSB) and Netherlands Railways (NS). The results highlight the strengths and weaknesses of the considered approaches.