An Application of the Semi Markovian Decision Approach for Train Conflict Resolution on a Vital Dutch Railway Section
A Al-Ibrahim, J van der Wal, University of Amsterdam, NL; R Klein Schiphorst, Prorail, NL
Many delays at railways arise from train conflicts. Efficiently Solving these conflicts can result in huge improvements on punctuality of trains. A lot of research is being conducted in this area and different approaches have been considered. In this paper we discuss a novel approach based on a Semi-Markovian Decision (SMD) technique. To our knowledge this approach has never been applied to railway problems before. The approach has some advantages in comparison to other techniques; The SMD's stochastic nature allows for incorporating the effects of current decisions on future arrivals. This way the trains will suffer less from the previous decisions which is very difficult to implement in other approaches. Moreover, since the large masses of the trains (especially that of the freight trains) the acceleration time losses of trains are considered as part of decision making together with the train speeds, the location of trains within the model and the statistical information about future arrivals. A drawback of the approach is that the state-space tends to grow exponentially as the complexity of the model increases. Thus, a balance between these aspects needs to be found.
In cooperation with Prorail, the Dutch railway infrastructure manager, a vital section is selected which is considered as one of the busiest in the Netherlands and one where conflicts do arise very often. In this paper, we will first discuss how a railway conflict resolution problem can be translated to the SMD formulation and will then apply this model on the selected section. By means of an extensive simulation study we will compare the performance of our SMD strategy with that of some heuristics and with the so called TAD strategy which is the conflict resolution strategy used by Prorail nowadays in the Netherlands.
Association for European Transport