Train scheduling desynchronization and power peak optimization in a subway system

Simultaneous train departures can induce important power peaks in subway systems. In this paper, the authors study the possibility of optimally reducing instantaneous power peaks by slightly delaying scheduled train departures. The problem consists of finding the optimal set of delays to reduce the maximum peaks seen at the system substations subject to frequency, safety and operation constraints. The problem was mathematically defined and solved by an heuristic approach based on a deterministic simulation of the system and an optimization module. The solutions found using rush-hour data yield up to 17% power economy over the current situation. This economy is achieved at little expense in terms of transit line delay: a maximum of 25 seconds of total cumulated delay was found for an individual train