A Timetable-Dependent Method for Railway Capacity Analysis: Validation and Case Studies

The paper describes a timetable-dependent method for assessing railway capacity, based on the generation and the analysis of sets of feasible timetables. This approach permits to consider all the major variables which characterise railway operations, together with their mutual interactions. These variables are evaluated as key performance indexes of nominal and operational timetables. The first are automatically generated by an heuristic greedy scheduling algorithm, while operational ones are provided by the discrete event simulation of traffic perturbations. The article focuses on two applications of this method. A comparison is carried out with a similar method - already presented in literature – which is based on a commercial software, providing an effective validation. Making use of a virtual case study, different approaches for obtaining “seeds” for the generation of feasible timetables are presented and discussed, pointing out their actual capability of being applied to real case studies and of encompassing different solutions. This case study is therefore used for presenting an analysis of the influence of buffer time on timetable stability. Finally an application for determining the capacity saturation limit of a line is presented. Timetables featuring a raising number of daily/hourly trains are simulated, tracking the trend of the timetable performance indexes. Considerations are presented, regarding the way of interpreting this trend for obtaining the practical capacity limit.