Horizontal Cooperation in Dial-a-Ride Services

Abstract

A dial-a-ride system is an application of demand-dependent, collective people transportation. Users request a trip between an origin and a destination of choice, to which service level requirements are linked. The service provider attempts to develop efficient vehicle routes and time schedules, respecting these requirements and the technical constraints of a pickup and delivery problem. Given the ageing population, dial-a-ride systems gain importance to complement regular transportation modes. The current practice consists in that users choose a provider to submit their request. Multiple providers operating in the same area solve separate routing problems based on the requests they received. However, research in freight transportation suggests that joint route planning, i.e., a sharing of requests and vehicle capacity among providers, may cause joint operational benefits. The present research determines whether these benefits also apply to people transportation, characterized by tighter quality requirements. A new large neighborhood search algorithm is designed to solve the joint route planning problem, taking an integrated decision on (1) the assignment of requests to service providers and (2) the allocation of vehicles among the depots involved. A real-life case study confirms that such horizontal cooperation reduces joint distance traveled and required fleet size, without compromising the service level. A pattern is observed in which requests are exchanged among providers.