Integrated Scheduling of Automated Rail-Mounted Gantries and External Trucks in U-Shaped Container Terminals

In this paper, the scheduling of yard cranes (YCs) and external trucks (ETs) working in a U-shaped automated container terminal yard is proposed as a new problem. This problem arises due to the characteristic of the U-shaped layout, where the ETs enter the yard through the U-shaped lanes and interact with the YCs. To formulate this problem, a three-objective optimization model is established to simultaneously schedule YCs and ETs, considering their efficiencies. Its solution is based on the nondominated sorting genetic algorithm III (NSGA-III), which is improved during initialization, crossover and mutation to make it applicable to the problem. To calculate the objective values in each iteration of the NSGA-III, a method to make the equipment interactions equal at all times is proposed. As there are special requirements for the priority of the objectives, a new method of selecting the final solution is presented, which leads to a more suitable solution. The case study involving sensitivity analysis shows that appropriate equipment quantity arrangement and task assignments have a positive impact on improving the efficiency of yard operations. Experimental results demonstrate that the proposed model and algorithms perform better. In summary, the model and algorithms proposed in this paper can effectively solve the proposed problem, which can offer a variety of options for decision-makers in an actual terminal operation environment. Note to Practitioners—The YC scheduling of a U-shaped layout presents new characteristics, and the influence of ETs cannot be ignored, posing a novel problem. Furthermore, during the operation of container terminals, extended waiting time for ETs is often caused by considerations related to ship schedules, especially in the mixed stacking mode. This can frustrate cargo owners and waste valuable ET resources. Hence, this paper designs a joint scheduling strategy for YCs and ETs in U-shaped yard layouts. The proposed strategy combines optimizing YC operation plans with maximizing ET efficiency, while ensuring efficient yard operations.