Dispatching and coordination in multi-area railway traffic management

This paper deals with the development of decision support systems for traffic management of large and busy railway networks. Railway operators typically structure the control of complicated networks into the coordinated control of several local dispatching areas. A dispatcher takes rescheduling decisions on the trains running on its local area while a coordinator addresses global issues that may arise between areas. While several advanced train dispatching models and algorithms have been proposed to support the dispatchers’ task, the coordination problem did not receive much attention in the literature on train scheduling. As far as decision support systems are concerned, the control of a railway network can be achieved either by a centralized approach in which the whole scheduling problem is solved by a single scheduler, or by a distributed approach in which a coordinator sets constraints between areas and delegates scheduling decisions to local schedulers. This paper compares centralized and distributed procedures to support the task of dispatchers and coordinators. We adopt dispatching procedures driven by optimization algorithms and based on local or global information and decisions. Computational experiments on a Dutch railway network, actually controlled by ten dispatchers, assess the performance of the centralized and distributed procedures. Different types of traffic disturbances, including entrance delays and blocked tracks, are analyzed on various time horizons of traffic prediction. Results show that the centralized procedure faces increasing difficulty in finding feasible solutions in a short computation time. For seriously disturbed instances with a permanent track blockage, the distributed approach is more suitable than the centralized one in order to manage traffic in the overall area.