A Constraint-Based Scheduling Model for Optimal Train Dispatching

Railway networks are faced to an increase demand of new services. This situation leads to train schedules close to the maximum capacity of the infrastructure. As the extension of the infrastructure is too expensive, an alternative solution is to improve traffic management in congested areas. This task can be formulated as an optimization problem which is a joint scheduling and allocation problems. The problem is considered to be a NP-hard problem which makes it difficult to solve using exact methods for a reasonable problem size. In this paper, we compare two heuristic methods for solving the problem. The first one uses a two-phase approach to perform independently resource allocation and scheduling. The second one performs incrementally the two kind of decisions at track section level, i.e. at each step, the algorithm performs decisions of allocation of a track section or of scheduling a pair of train runs on this section.