Checking the Feasibility of Dial-a-Ride Instances Using Constraint Programming

In the dial-a-ride problem (DARP), a fleet of vehicles must serve transportation requests made by users that need to be transported from an origin to a destination. In this paper we develop the first exact algorithm which is able to either efficiently prove the infeasibility or to provide a feasible solution. Such an algorithm could be used in a dynamic setting for determining whether it is possible or not to accept an incoming request. The algorithm includes solution space reduction procedures, and filtering algorithms for some DARP relaxations. Computational results show that the filtering algorithms are effective and that the resulting algorithm is advantageous on the more constrained instances.