Using a general-purpose Mixed-Integer Linear Programming solver for the practical solution of real-time train rescheduling

At a planning level, train scheduling consists of optimizing the routing and scheduling for a set of trains on a railway network. In real-time operations, however, the planned schedule constantly needs to be verified and possibly updated due to disruptions/delays that may require train rerouting or cancelation. In practice, an almost immediate reaction is required when unexpected events occur, meaning that trains must be rescheduled in a matter of seconds. This makes the time-consuming optimization tools successfully used in the planning phase completely inadequate, and ad-hoc (heuristic) algorithms have to be designed. In the present paper we develop a simple approach based on MixedInteger Linear Programming (MILP) techniques, that uses an ad-hoc heuristic preprocessing on the top of a general-purpose commercial solver applied to a standard event-based MILP formulation. A computational analysis on real cases shows that our approach can be successfully used for practical real-time train rescheduling, as it is able to deliver (almost) optimal solutions within the very tight time limits imposed by the real-time environment.