Running time re-optimization during real-time timetable perturbations

Abstract

This paper describes how, in the Netherlands, the railway network is heavily used by heterogeneous train traffic and characterized by short headway times. That is why even small initial delays may perturb the timetable causing consecutive delays. In such conflict situations, traffic controllers have the complicated task to decide upon the optimal train schedule in real-time. They could be assisted by sophisticated conflict-solving systems. Optimal train running profiles can be designed which fit better to the new train order and allow reducing delays and energy consumption at the same time. The paper presents a formulation for this complex problem that makes it suitable for quantitative analysis and for optimizing actual running times at network scale. A conflict solution system is developed, that models the train scheduling problem as an alternative graph. Adopting the blocking time model, safe headway distances between trains are assured by any real-time traffic control measure. The optimal solution from a network point of view can be improved by modifying the speed profiles locally for the individual train routes. A constructive heuristic algorithm for the dynamic modification of running times during operations is proposed that satisfies the timetable constraints of train orders and routes and guarantees the feasibility of the running profile, while taking into account the properties of the signaling and train protection systems in use. A real-world example from the Netherlands in case of the Dutch signaling system NS54 is presented to demonstrate the benefits of the proposed methodology.