Location Design and Relocation of a Mixed Car-Sharing Fleet with a CO2 Emission Constraint
Car-sharing companies have shown increasing support in the adoption of fuel efficient cars to reduce CO2 emissions and to meet heterogeneous demand. In this paper, we consider location design and relocation problems for sharing a mixed fleet of cars and propose integer linear programs that incorporate both one-way and round-trip demand and operations. To model car movements, we use a minimum-cost flow model on a spatial–temporal network given time-based demand. We maximize the total profit of renting cars minus the cost of relocation and maintenance, subject to limited budget for purchasing cars and given a CO2 emission limit. In addition, we enforce the first-come, first-served principle to eliminate denied trips. We conduct computational studies based on 2014 Zipcar data in Boston to provide insights for fleet location, car-type designs, and their environmental impacts. Our results show high utilization of cars and low demand losses and denied trips. Although the CO2 emission limit may lower car-sharing profit, high demand on new energy-efficient cars can compensate the loss and is worth being satisfied.