An exact method for the two-echelon location-routing problem

The two-echelon location-routing problem is a literature classic particularly focused on last-mile delivery. This problem involves facility location and vehicle routing in two echelons. It reflects the operational reality of many logistics networks, especially those in which there are deliveries in large urban centers. This problem has been largely studied with the proposal of optimization algorithms and extensions to the original problem. Nevertheless, to the best of our knowledge, no exact algorithm based on column generation has ever been proposed for this problem. In this work, this gap in the literature is filled, with the proposal of an algorithm capable of closing seventeen instances still open in the literature.