Large neighborhood search with constraint programming for a vehicle routing problem with synchronization constraints

This paper considers an extension of the vehicle routing problem with time windows, where the arrival of two vehicles at different customer locations must be synchronized. That is, one vehicle has to deliver some product to a customer, like a home theater system, while the crew on another vehicle must install it. This type of problem is often encountered in practice and is very challenging due to the interdependency among the vehicle routes, but has received little attention in the literature. A constraint programming-based adaptive large neighborhood search is proposed to solve this problem. The search abilities of the large neighborhood search and the constraint propagation abilities of constraint programming are combined to efficiently determine the feasibility of any proposed modification to the current solution. Numerical results are reported on instances derived from benchmark instances for the vehicle routing problem with time windows with up to 200 customers.