Cooperative Variable Neighborhood Search for the Vehicle Routing Problem with Simultaneous Pickup and Delivery

The vehicle routing problem with simultaneous pickup and delivery (VRPSDP) is a common transportation problem where a fleet of vehicles deliver goods from the depot to line haul customers and pick up goods from backhaul customers to the depot. This problem variation allows vehicles to make the delivery and pickup operations on same time by visiting all clients once with the aim of minimization of total travel distance. In this study, a very efficient cooperative variable neighborhood search (CVNS) is proposed to solve the problem. In this parallel search approach, variable neighborhood search (VNS), savings heuristic and perturbation mechanism are combined with the help of parallelization strategies. The proposed approach is able to solve a number of well-known benchmark instances by providing superior solutions compare to those reported in the literature.