Metaheuristic approaches for the vehicle routing problem with time windows and multiple deliverymen

In this paper, we address the vehicle routing pro blem with time windows and multiple deliverymen, a variant of the vehicle routing probl em which includes the decision of the crew size of vehicles, besides the usual scheduling and routing decisions. This problem arises in the distribution of goods in congested urban areas, where due to the re latively long service times it may be difficult to serve all customers during regular working hours. G iven this difficulty, an alternative consists in recurring to additional deliverymen to reduce the s ervice times, which typically leads to extra costs in addition to travel and vehicle usage costs. The obj ctive is to define routes for serving clusters of customers, while minimizing the number of routes, t he total number of assigned deliverymen and the traveled distance. To solve this problem, we propos e two metaheuristic approaches based on Iterated Local Search and Large Neighborhood Search. The per formance of the approaches is evaluated using sets of instances from the literature.