ILS with Multiple Variable Neighbourhood Descendent for the Vehicle Routing Problem with Multiple Trips

This paper describes a new approach to solving the vehicle route problem with Multiple Trips. The proposed algorithm (IVNDS) is based on the Iterative Local Search meta-heuristic which uses two consecutive Variable Neighbourhood Descendent (VND) procedures in the improvement phase. The VND procedures are differentiated by the search spaces they explore. The first VND performs moves in routes of the same vehicle and the second one relocates customers to routes of different vehicles. The algorithm has been tested against well-known benchmark instances and the results obtained are competitive with previous approaches found in the literature.