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Traditional car sharing systems are round trip shared vehicle systems and require advance reservations. The advances of GPS, communication techniques and vehicle automation allow us to improve car-sharing systems and to provide users with greater flexibility. As it concerns reservation, new car sharing systems offer users open-ended reservation and/or instant access. As it concerns the trip topology, new car sharing systems are multiple station shared vehicle systems (MSSVS). Round trips still occur in this type of system; however there are a large number of one-way trips made between the multiple stations. Operating an MSSVS is much more difficult than operating a round trip shared vehicle system. The problem is that the system can quickly become imbalanced with respect to the number of vehicles at the multiple stations. A review of user-based and operator-based relocation strategies is provided in the paper, as well as some details about some new possible car sharing systems, where vehicles are fully automated and can be accessed from any point within the intervention area.

Purpose The paper concerns a transport system for pedestrian areas, based on a fleet of fully-automated Personal Intelligent Accessible Vehicles. The following services are provided: instant access, open ended reservation and one way trips. All these features provide users with high flexibility, but create a problem of uneven distribution of vehicles among the stations. A fully vehicle based relocation strategy is proposed: when a relocation is required vehicles automatically move among stations. The paper focuses on a methodology that allows to plan the proposed transport system for wide pedestrian areas. The methodology aims to determine the fleet dimension and the relocation strategy parameters which minimize the system cost. The system cost takes into account the level of service and the efficiency. Relocation strategy parameters define when and among which stations relocations should be performed. Methods The problem faced is an optimisation problem where the search space is defined by all the possible fleet dimensions and relocation strategy parameters. As this cost function could be a multipeak function and since the search space is discrete and extremely large, a random search algorithm has been adopted. Because of the characteristics of the problem, a parallel optimization technique was required. Given a fleet dimension and relocation strategy parameters, a microsimulator models the activity of each user, as well as the activity of each vehicle over time with the aim of finding the level of service and the system efficiency.Results, conclusions and application The methodology has been applied to planning the proposed transport system for the centre of Barreiro, Portugal.