Heuristic for vehicle routing problem with perishable product delivery

The purpose of Vehicle Routing Problem (VRP) is to design the least costly (distance, time) routes for a fleet of identically capacitated vehicles to serve geographically scattered customers. There may be some restrictions such as the maximal capacity for each vehicle, maximal distance for each vehicle, time window to visit the specific customers, and so forth. This paper is concerned with VRP to minimize the sum of elapsed time from departure, where the elapsed time is defined as the time taken in a moving vehicle from the depot to each customer. It is important to control the time taken from departure in the delivery of perishable products or foods, whose freshness may deteriorate during the delivery time. An integer linear programming formulation is suggested and a heuristic for practical use is constructed. The heuristic is based on the set partitioning problem whose performances are compared with those of ILOG dispatcher. It is shown that the suggested heuristic gave good solutions within a short computation time by computational experiments.