Routing a heterogeneous fleet of vehicles

In the well-known Vehicle Routing Problem (VRP), a set of identical vehicles, based at a central depot, is to be optimally routed to supply customers with known demands subject to vehicle capacity constraints. An important variant of the VRP arises when a fleet of vehicles character-ized by different capacities and costs, is available for distribution activities. The problem is known as the Mixed Fleet VRP or as the Heterogeneous Fleet VRP. This paper gives an overview of approaches from the literature to solve het-erogeneous VRPs. In particular, we classify the different variants described in the literature and, as no exact algorithm has been presented for any variants of heterogeneous VRP, we review the lower bounds and the heuristic algorithms proposed. Computational results, comparing the performance of the different heuristic algorithms on benchmark instances, are also discussed