Shunting scheduling method in a railway depot for dealing with changes in operational conditions

A shunting schedule in a railroad depot consists of instructions to allocate or move train-units in the field. In this paper, we propose a scheduling method which can reconstruct solution in response to various changes in operational conditions. Under classification of train-units to be re-scheduled into two sets; one is a group of having invalid schedule (ISU) and another is a group of having valid schedule (VSU), the method is escalating the re-scheduling target by adding ISUs to a set of VSU and repeatedly solving a partial problem of the target until all the unit is processed. Based on the mathematical model which formalizes the problem as a kind of Flexible Job Shop Scheduling Problems (FJSSP), and two phase search process composed of resource allocation and time setting, the partial solution can be derived by an algorithm which uses Constraint Programming (CP) with domain-oriented heuristics. The proposed method was applied to three imaginary depots which have different layout structures each other (Fig.1) and tested numerically under several conditions. Fig.2 is an example of shunting schedulue made by the proposed method to Depot A. Feasible solutions of all the three depots can be generated from scratch, which means mak-