A MILP model to improve the robustness of a railway timetable by retiming and rerouting in a complex bottleneck area

Robustness is a crucial concept in railway timetabling. It is often related to the ability of a timetable to absorb small delays. We propose a MILP model to improve the robustness of an existing microscopic timetable in a complex and heavily used part of the network. The objective is to maximise the buffer times between each pair of trains, leading to a good spreading in time of the trains. Focusing on this objective will lead to less propagation of delays and therefore shorter and more reliable travel times for the passengers. The model can adapt both the timing and the routing of the trains. However, to ensure that the proposed timetable is practically relevant for the railway companies, constraints can be added easily depending on the properties that the resulting timetable should have. Due to the flexibility of the proposed model, it can also be used to analyse and optimise alternative scenarios. The model is applied to a case study of a bottleneck area of the Belgian railway network, located just outside of Brussels, where the traffic is very heterogeneous. The results show that the spreading objective can be improved with 18% compared to the current situation.