Quantifying the Efficiency of Ride Sharing

In unit-capacity mobility-on-demand systems, the vehicles transport only one travel party at a time, whereas in ride-sharing mobility-on-demand systems, a vehicle may transport different travel parties at the same time, e.g., if paths are partially overlapping. One potential benefit of ride sharing is increased system efficiency. However, it is not clear what the trade-offs are between the efficiency gains and the reduction in quality of service. To quantify those trade-offs, an open-source simulation environment is introduced, which is capable of evaluating a large class of operational policies for ride-sharing mobility-on-demand systems. The impact of ride sharing on efficiency and service level is assessed for several benchmark operational policies from the literature and for different transportation scenarios: first a dense urban scenario, then a line-shaped, rural one. Based on the results of these case studies, we find that the efficiency gains in ride sharing are relatively small and potentially hard to justify against quality of service concerns such as reduced convenience, loss of privacy, and higher total travel and drive times. Furthermore, in the assessed scenarios, the relatively low occupancy of the vehicles suggests that smaller vehicles with 4–6 seats, able to handle occasional ride sharing, may be preferable to larger and more expensive vehicles such as minibuses.

I. Introduction

Mobility-on-Demand (MoD) transportation systems promise to combine the convenience of motorized individual transport with the environmental friendliness and price of conventional public transit [1]. In this work, we consider coordinated MoD systems, in which there are no autonomous decisions at the vehicle level, thereby ruling out uncooperative behavior; this corresponds to the category of “dynamic real-time ridesharing” systems described in [2] with the additional condition that the vehicles belong to an operator, not the users. Such systems have the potential to improve existing transportation systems in many ways, e.g., by increasing accessibility [3], improving public transportation in rural areas [4], and lowering cost for users [5].