An MIP-based heuristic solution approach for the locomotive assignment problem focussing on (dis-)connecting processes

Arising from a practical problem in European rail freight transport we present a heuristic solution approach that is based on a new generalized mixed integer problem formulation for the Locomotive Assignment Problem. A main focus is on the one hand on the (dis-)connecting processes between cars and locomotives and on the other hand on combining two or more locomotives, i.e., the process of building and busting consists (combination of locomotives). Furthermore, regional limitations for running certain types of locomotives and technical conditions for combining locomotives are taken into account. A generalized solution framework is developed that allows a gradual restricting of the solution space and enables an analysis and comparison of different solution procedures. Testing these for a real-world network as well as several newly generated instances shows that the framework outperforms previous approaches in the literature. Thus a suitable solution method for an application in practice is presented. (C) 2020 Elsevier Ltd. All rights reserved.