The Assignment of Customers in Multi-depot Vehicle Routing Problem with Fleet Size Constraint for Each Depot

This paper addresses a multi-depot vehicle routing problem with partial customers not yet assigned to depots and each depot having fleet size constraint. An integrated mathematical model has been constructed with the objective of minimizing both the total required fleet size and overall traveling distance. To overcome the computation difficulty resulting from high order mathematic model, the problem is decomposed into two sub-problems. Moreover, to keep the consistency between decomposed problems and original problem, partial decision of the second sub-problem is taken into the consideration of the first sub-problem. For larger instances, two heuristics have also been developed. The computation results tested on real-life data of auto spare parts show that taking partial second decision into the consideration of the first decision does improve solution quality and the heuristics could provide encouraging methods for practical use.