Railway freight node capacity evaluation: A timetable-saturation approach and its application to the Novara freight terminal

This paper presents a timetable-based approach to assess the capacity of a railway freight node, based on the microscopic simulation and saturation of the timetable. Saturation is done by scheduling additional saturation train paths without introducing any traffic conflict, while respecting the required technical and operational constraints, until no more paths can be added. The approach is applied to analyze the potential effects on capacity of some infrastructure improvements planned by Rete Ferroviaria Italiana (RFI) for the rail freight node of Novara, Italy. The capacity is evaluated by means of two KPIs computed on saturated timetables: the number of daily pairs of saturation freight trains and the infrastructure Occupancy Time Rate (OTR). The first KPI represents an absolute estimation of the capacity (theoretical or practical, depending on the presence of buffer times). Instead, the OTR is computed by the UIC 406R compression method and it is used to identify local bottlenecks. For the analysis, we use SASTRE, an analysis environment for railway systems developed at Politecnico di Torino, which combines a MILP formulation for the timetable saturation problem with a saturation strategy layer. The saturation strategy considers a given set of priorities between the different network areas and the train types to be used during the saturation process. The results reveal that using a microscopic model to schedule traffic flows on a complex railway node allows for a good accuracy of the timetable, but at a high computational cost.