In the kind of transportation system studied in this paper, cars are placed at the disposal of subscribers (customers) in stations. Customers have access to the cars using non-contact smart cards. They can use a car for a while and return it in the same or another station. At some times of the day, either an overflow or a shortage of cars may happen at one or more stations. The balancing process consists of redistributing the cars among the stations in order to avoid overflow and shortage, that is to guaranty a service ratio that is as high as possible, taking into account the number of cars available in the system. The goal of this paper is to make a systematic analysis of the balancing process and to propose an efficient balancing heuristic algorithm
