Journal of Intelligent Transportation Systems: Technology, Planning, and Operations

ABSTRACT Carsharing systems are an alternative to private transportation whereby a person may use an automobile without having to own the vehicle. The classical systems in Europe are organized in stations scattered around the city where a person may pick-up a vehicle and afterwards return it to the same station (round-trip). Allowing a person to drop-off the vehicle at any station, called one-way system, poses a significant logistics problem because it creates a significant stock imbalance at the stations, which means that there will be times when users will not have a vehicle available for their trip. Previous mathematical programming formulations have tried to overcome this limitation by optimizing trip selection and station location in a city in order to capture the best trips for balancing the system. But there was one main limitation: the users were assumed to be inflexible with respect to their choice of a station, and held to use only the one closest to their origin and destination. If the user is willing to use the second or even the third closest station he could benefit from using real-time information on vehicle stocks at each station and be able to select the one with available capacity. In this paper we extend a previous model for trip selection and station location that takes that aspect into account by considering more vehicle pick-up and drop-off station options and then apply it to a trip Origin-Destination matrix from the Lisbon region in Portugal. Through the extended formulation we were able to conclude that user flexibility allied with having information on vehicle stocks increases the profit of the company as people will go directly to a station with a vehicle available thus making the use of the fleet more efficient. Observing the size of the stations resulting from the model we also concluded that the effect of information is enhanced by large carsharing systems consisting of many small stations.