A tabu search heuristic for the vehicle routing problem with time windows and split deliveries

The routing of a fleet of vehicles to service a set of customers is important in the field of distribution. Vehicle routing problems (VRP) arise in many real-life applications within transportation and logistics. In this paper, we study a variant of the general VRP, VRP with time windows and split deliveries (VRPTWSD). Time constrained routing is relevant for applications where a schedule has to be followed. The option of splitting a demand makes it possible to service a customer whose demand exceeds the vehicle capacity. Splitting also allows to decrease costs. Although VRPTWSD is a relaxation of the VRP with time windows, the problem does not become easier to solve, and is still NP-hard. In this work, we propose a solution method based on tabu search for solving the VRPTWSD without imposing any restrictions on the split delivery options. We also give an analysis of experimental results on problems with 100 customers.