Coordination of truck departure times and scheduling the unloading operations in Aras kargo Ankara transfer center

The problems related to parcel delivery have started receiving attention in the literature in recent years. Determination of the vehicle routes for desired service levels, network design, consolidation decisions, operational planning of transfer centers are commonly studied problems. This study addresses the coordination of the vehicle departure times from branches and the scheduling of the inbound vehicles to unloading gates at a central cross docking terminal of Aras Kargo. The objective is to maximize the weighted sum of vehicle departure times. The main constraint is to finish up the unloading operation of all vehicles until a target completion time. Integer programming is used for modeling the problem. The mathematical model, which is developed for different confidence levels, is based on a previously proposed model for the parallel machine scheduling problem. Because of the complexity of the problem, a two-phase heuristic approach is proposed. The heuristic approach first solves the assignment problem of vehicles to unloading gates using the linear relaxation of the model, and then it addresses the scheduling problem for each door separately. The efficiency of the heuristic approach is shown by numerical experiments. Additionally, for the purpose of observing the effects of uncertainty in the system and including the dynamic structure of the queue formation, a simulation model is developed. Using the simulation model, the effects of delays on truck departure times, optimization of the truck departure times, the increase in demand and relevant door assignment alternatives are examined. The results of the mathematical and simulation model are compared with each other as well.