A Hybrid Metaheuristic Method for Two-Echelon Location-Routing Problem with Pickup and Delivery

Integrated optimization approach in supply chain has become one of the most important and interesting subjects for researchers in recent years. In this paper, a mathematical model is presented for two-echelon location-routing problem with simultaneous pickup and delivery, so that a layer of facilities with the name of “middle warehouse” are located between main distribution centers and customers. Each customer has demands for commodity reception and delivery simultaneously. In this paper, first a two-echelon integer programming mathematical model, which central/middle storerooms capacities are considered limited, is presented. Then, using genetic and simulated annealing algorithms, a hybrid metaheuristic method is delivered for solving the model. Numerical results of solving sample instances in different sizes confirm the good performance of our approach.