Model for the multiple depots heterogeneous dial-aride problem with flexible depots

This paper studies a new dial-a-ride problem (DARP) called multiple depots heterogeneous dial-a-ride problem with flexible depots (MHDARP-FD), which considered multiple depots, heterogeneous vehicles and users, and flexible depots. The assumption of flexible depots allows the vehicle to end its route at any depot. As a result, the total travel cost may be reduced. A mixed integer nonlinear programming model was firstly formulated for the considered problem. To make the MHDARP-FD tractable, the original model was reformulated by linearizing constraints, aggregating variables, and strengthening model. The new model is solved by the state-of-the-art IP solver CPLEX. Computational results of numerical experiments show the validity of the proposed model and its effectiveness for addressing realistic problem.