Section: New Results

Railway Time Tabling Optimization

Participants : François Fages, David Fournier, Thierry Martinez, Sylvain Soliman.

Metros are able to generate electricity on a metro line by braking. This energy is immediately available in the third rail and is lost if no metro in the neighbourhood can consume it. It is thus possible to decrease the total energy consumption of a metro line by synchronizing the accelerations and braking of the metros. In [2] , [9] , we propose a classification of energy optimization timetable problems and we present a model for optimizing energy consumption which does not significantly alter the quality of service, by subtly modifying dwell times. We show however that this optimization problem is NP-hard. We present a hybrid genetic/linear programming algorithm for computing the distribution of braking metros. In this hybridization, the objective function is computed by a linear program and by a heuristic, and the dwell times are modified by a genetic algorithm. On a typical example with real data, the savings exceed 7%. Furthermore, on a benchmark of the literature for a simpler problem, we discuss the results obtained with our genetic algorithm, a tabu search algorithm and the mixed integer linear program used by the authors.