Station-Based or Free-Floating? An Integrated Carsharing System with Dual Service Types

A specific service type is applied by most one-way carsharing operators, either station-based or free-floating, which depends on whether users are required to pick up and return vehicles in fixed parking lots. However, both of them have inherent limitations. The station-based carsharing system encounters the weakness of low parking-space utilization, whereas the free-floating system needs to face high parking and relocation costs. To overcome the limitations of single-type carsharing systems, this paper proposes an integrated system to apply the two types in different parts of the service area. A mixed-integer linear-programming model is established to maximize the operator profit, considering both strategic decisions of service type and operational decisions of relocation and trip selection. Despite the fact that the model can be solved by the CPLEX solver, it is limited by excessive memory usage and too long solving time in large-scale cases. To enhance the solving feasibility of the proposed model, a heuristic algorithm is proposed to effectively iterate feasible strategic options and solve the operational subproblem. The numerical results of the case study show that the proposed algorithm can achieve comparable objectives with the CPLEX solver in a much shorter computational time. Through system comparison, the integrated system achieves a larger profit and higher demand-fulfillment rate, compared with the single station-based or free-floating system.