A Branch-and-Cut Algorithm for the Single Truck and Trailer Routing Problem with Satellite Depots

In the single truck and trailer routing problem with satellite depots (STTRPSD), a truck with a detachable trailer based at a main depot must serve the demand of a set of customers accessible only by truck. Therefore, before serving the customers, it is necessary to detach the trailer in an appropriate parking place (called either a satellite depot or a trailer point) and transfer goods between the truck and the trailer. This problem has applications in milk collection for farms that cannot be reached using large vehicles. In this work we present an integer programming formulation of the STTRPSD. This formulation is tightened with several families of valid inequalities for which we have developed different (exact and heuristic) separation procedures. Using these elements, we have implemented a branch-and-cut algorithm for the solution of the STTRPSD. A computational experiment with published instances shows that the proposed branch-and-cut algorithm consistently solves problems with up to 50 customers and 10 satellite depots, and it has also been able to solve instances with up to 20 satellite depots and 100 clustered customers.