Infrastructure design for robust operations on railway corridors – Quantifying the combined effects of overtaking tracks and dispatching strategies

Railway infrastructure in densely utilized European networks is coming under increasing stress, especially on main traffic corridors shared by passenger and freight services with different speed profiles and stopping policies. Siding tracks allowing to change the train order are important design features to optimize capacity and to ensure robustness by allowing to schedule more trains with different characteristics and to adjust train order in operations. This work presents a comprehensive analysis of the relationship between infrastructure layout, dispatching policy, and operational stability for double-track railway lines, investigating the effect of additional overtaking tracks on the performance of rail corridors. A timetable-ensemble generating approach is used and the operational robustness is evaluated using mesoscopic discrete-event simulation of train operations on the corridor considering a set of typical dispatching heuristics observed in practice. The method is then applied in a case study for a railway corridor in Southern Germany and the robustness of the infrastructure design is evaluated as a function of the strength of perturbations. Overall, the study demonstrates the importance of well-designed dispatching strategies for simulation-based scenario evaluation and shows how the benefit of additional overtaking tracks depends on timetable heterogeneity, traffic load, and the level of primary delays.