Impact of ride-pooling on the nature of transit network design

This paper examines the basic design trade-off in six distinctive transit systems, including two state-of-the-art fixed-route systems and four hybrid systems that use ride-pooling as an integrated feeder service. The systems are analyzed using a continuous approximation approach, and the resulting optimal design problem is formulated and solved as a mixed integer program. We find that ride-pooling changes little the fundamental laws inherent in transit design. Specifically, all six systems, despite their seemingly vastly different design features, display the following laws: (1) that the per capita agency cost correlates linearly with the per capita user cost, (2) that both costs are power functions of the demand density with an exponent close to −13 and −0.4 for agency and user costs, respectively, and (3) that the per capita agency cost is not significantly affected by city size but the user cost is. This finding suggests that ride-pooling may have a rather limited impact on the economy of scale in mass transit systems. However, mixing ride-pooling with fixed-route services does promise modest improvements to the overall system efficiency. It also tilts the balance of trade-off considerably in the user’s favor, at the operator’s expense.