Design of a new railway scheduling model for dense services

We address the problem of generating a global detailed conflict-free railway schedule for a given set of train lines and frequencies and we propose a decomposition of the railway network into condensation and compensation zones in order to solve the train scheduling problem. Condensation zones lie in the proximity of main stations, where available capacity is limited and trains are therefore required to travel with maximum speed. On the other hand, traffic is less dense in the compensation zones, which connect the condensation zones. Thus, time reserves can be introduced to train runs in compensation zones in order to increase stability of the timetable. Each zone is then dealt with according to its specific properties. In this paper we focus particularly on the timetabling and routing problem in condensation zones. In order to gain structure in the schedule and therefore simplify the dispatcher’s work, we introduce a policy to schedule trains using a time discretisation. The problem is modeled as an independent set problem in a conflict graph, which is then solved using a fixed-point iteration heuristic. Results show that even large-scaled train scheduling problems with dense timetables and large stations can be solved within a minute.