Introduction to the special issue on shared mobility systems

An increased use of shared mobility systems such as bike sharing, ride sharing or car sharing is evident in recent years. These systems gain popularity as an alternative to using private vehicles since they have the advantage of reducing traffic congestion, parking space shortage, and air pollution. Shared mobility systems serve as a good complementary to mass transit systems, for example, as a convenient solution to the first and last miles of a journey. In addition, members of vehicle sharing programs have a lower tendency to own a private car. Designing and operating vehicle sharing systems raises many interesting challenges. These problems range from long-term strategic issues to on-line operational decisions. On the strategic end of the spectrum, there are questions such as the economical, technological, and environmental viability of deploying new car or bike-sharing systems in a city. There are various possible modes of operation of vehicle sharing system: it can be station-based or free-float, round-trip or one-way (A to B). Next, the stations’ location and capacity should be determined and at a more tactical level, pricing incentives and reservation policies should be set. Finally, at the operational level, vehicles’ and stations’ maintenance as well as repositioning/ rebalancing decisions should be taken on a daily basis and sometimes in real time. Various tools may be used to solve the above problems: forecasting using statistical and data mining methods, stochastic modeling, simulation and optimization using exact and heuristic methods. Vehicle sharing systems use modern