Integrated scheduling of yard cranes, external trucks, and internal trucks in maritime container terminal operation

The operations of yard cranes, external trucks and internal trucks in a maritime container terminal have an important impact on the operational efficiency of the terminal. A multi-objective optimization model is formulated in this paper, with a novel truck-based partition strategy, for a multiple-yard-crane scheduling problem, whose objective is to minimize both total longitudinal distance of yard cranes and total waiting time of internal and external trucks. The proposed model solves the truck assignment subproblem and the yard crane routing subproblem simultaneously to figure out how the trucks are to be served in an optimal manner by each yard crane and the optimal rank of each truck by which each yard crane provides container handling services in order. The effectiveness of the integrated truck-based and block-based scheduling strategies is validated by comparing with the existing strategies. Both the integrated block-based and the integrated truck-based scheduling strategies balance the two conflicting objectives better than the prioritized scheduling strategy and the first-come-first-served scheduling strategy. Numerical experiments shows that the advantage of the two integrated strategies is related to the ratio of the number of yard cranes to the number of container blocks. Some implications for port operation policy are also discussed.