Section: Contracts and Grants with Industry

SNCF

Participants : Laurent Gely, Philippe Meurdesoif, Arnaud Pêcher, Pierre Pesneau, François Vanderbeck.

Our contract with SNCF, “Innovation et Recherche” ended officialy in March. In previous work, L. Gély produced timetables in the aim of maximizing the throughput (number of trains) that can be handled by a given network [84] . In this project, we considered the problem of managing perturbations [83] . Network managers must re-optimize train schedules in the event of a significant unforeseen event that translates into new constraints on the availability of resources. The control parameters are the speed of the trains, their routing and sequencing. The aim is to re-schedule trains to return as quickly as possible to the theoretic timetable and to restrict the consequences of the perturbation to a limited area. The question of formulation is again central to the approach that shall be developed here. The models of the literature are not satisfactory. Continuous time formulations have poor quality due to the presence of discrete decision (re-sequencing or re-routing). Other standard models based on arc flow in time-space graph blow-up in size. Formulations in time-space graphs have therefore been limited to tackling single line timetabling problems. We have develop a discrete time formulation that strikes a compromise between these two previous models. Based on various time and network aggregation strategies, we develop a 2-stage approach, solving the contiuous time model having fixed the precedence based on a solution to the discrete time model.