# Logistics Distribution Vehicle Routing Problem with Time Window under Pallet 3D Loading Constraint
## 6 Conclusions  
This study addresses the problems of low distribution efficiency and susceptibility to bursting in the express delivery industry and proposes a 3D loading scheme for pallets based on a 3D loading scheme with pallets as intermediate carriers and flexible adjustment using pallets with retractable support structures. First, a dual-objective model with the highest vehicle loading rate and the lowest total cost of distribution is established and transformed into a single objective using a multi-objective linear weighting method. Next, spatio-temporal clustering was performed according to the customer nodes to obtain the better initial solution and generate the initial sequence; then, the demanded goods at the customer nodes were sorted from largest to smallest volume, and the initial sequence wasgenerated. Then, the bottom dimension of the standard pallet was used as the loading length and width constraint, and the height of the carriage was used as the height constraint. A hybrid simulated annealing-genetic algorithm was also used to perform the calculation of the 3D loading of the pallet. Based on the number of pallets, the weight of the goods, and the clustering results, a simulated annealing-genetic algorithm is used to calculate the pallet 3D loading scheme and the distribution path of the carriage. Compared with other studies, the loading rate of the three-dimensional loading algorithm is 2% lower than the method in reference [31], but it can save about 45% of the program running time. Compared with the traditional simulated annealing algorithm, it can have better stability. Finally, the paper analyzes the application of pallets as carriers in the delivery business of express delivery and compares the scheme without pallets. The experiment proves that the three-dimensional loading scheme using pallets can not only improve the loading and unloading speed but also ensure a higher loading rate. It can save 62.37% time cost under the loading rate of 81.68%. It is a scheme that uses less input to gain more benefits. Through experimental research, this paper solves the problems of the traditional three-dimensional loading scheme without an intermediate carrier, which is difficult to distinguish the cargo from the customer point, and low loading and unloading efficiency. The method of generating the initial solution according to the descending volume improves the loading rate of the hierarchical method and retains the computational efficiency of the hierarchical algorithm. The main contribution of this paper is that the use of pallets improves the efficiency of unloading and saves time cost. In the future, automation and standardization will be the trend of industrial production. The application of pallets to logistics distribution activities is more beneficial to the operation of mechanized equipment, which can also greatly improve the efficiency of distribution activities and make them more scientific and reasonable. Using hierarchical theory to study 3D loading can simplify the complexity of computer operation. Finally, this study proposes the pallets solution for loading to maximize the distribution loading rate and handling efficiency. However, there are still some future studies that should be involved: (1) The customer demand in this paper aims at the overall demand of customer points, but the express needs to be subdivided into the service time window of customer demand of each express, and the working time of express points should be reserved; (2) A lot of research on three-dimensional loading problems with different targets has been studied, such as cargo support, volume loading rate, weight loading rate, location of matching path in the carriage, the efficiency of the algorithm, consideration of center of gravity, etc.