Optimizing truck sequencing and truck dock assignment in a cross docking system

Cross docking plays a very importation role in supply chain management. The efficiency of cross docking will influence the lead time, inventory level and response time to the customer. This research aims to improve the efficiency of multi-door cross docking by optimizing both inbound and outbound truck sequencing and both inbound and outbound truck dock assignment. The objective is to minimize the makespan. The problem is new in the literature and no previous formulation of the problem can be found. In order to optimize the problem, a model for calculating the makespan is proposed. When given a sequence of all inbound and outbound trucks, the calculation model can assign all inbound and outbound trucks to all inbound and outbound doors based on first come first served and then calculate the makespan. The proposed makespan calculation model is then integrated with a variable neighborhood search (VNS) which can optimize the sequence of all inbound and outbound trucks. Four simulated Annealing (SA) algorithms are adopted for comparison. The experimental results show the proposed VNS provides 8.23–40.97% improvement over the solution generated randomly. Although it does not provide the best result for all problems when compared with SA algorithms, it provides robust results within a reasonable time. Thus the proposed method is efficient and effective in solving cross docking operation problems.