Relocation strategies and algorithms for free-floating Car Sharing Systems

During the last two years so-called free-floating Car Sharing Systems became very popular. These systems in comparison to the conventional Car Sharing Systems allow short one-way trips. Today, the spatial distribution of vehicles within free-floating Car Sharing Systems is either self-organized, which means it is only dependent on the customer´s demand or in a few cases the positioning is manually controlled by system operators. None of the known free-floating Car Sharing Systems has a clear defined relocation strategy or is online optimized based on the current demand. Within this paper several relocation strategies are introduced and categorized. For each category a relocation algorithm is described and evaluated. Also a new integrated two-step algorithm for optimal positioning and strategy selection is described in detail. This new approach consists of an offline demand clustering that allows for strategy pre-selection. The online module of the approach measures the differences between optimal vehicle positioning and current positioning and selects the best relocation strategy for implementation.