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

We consider the Train Unit Shunting Problem, an important plan- ning 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 Pro- gramming formulation, a Column Generation approach, and a random- ized greedy heuristic. We compare and benchmark these approaches against slightly adjusted existing methods based on a a Mixed Inte- ger Linear Program, and a Two-Stage heuristic. The benchmark con- tains multiple real-life instances provided by the Danish State Rail- ways (DSB) and Netherlands Railways (NS). The results highlight the strengths and weaknesses of the considered approaches.