Institute of Transportation Studies at UC Berkeley

This report compares the performance of three double-cycling algorithms used to determine the sequence with which to load and unload containers from a vessel with a quay crane. Double cycling is a technique which can improve the efficiency of a quay crane and container port by unloading and loading containers in the same crane cycle. The three algorithms, the greedy strategy, the proximal strategy, and Johnson’s rule, are introduced and results from applying the three strategies to a set of simulated vessels are compared. While Johnson’s rule provides the minimum number of cycles required to unload and load a vessel using double cycling, it is operationally less convenient. The proximal strategy is operationally convenient, but provides a smaller benefit when compared to single cycling. All strategies provide significant benefit (about a 40% reduction over single cycling for hatchless ships), and the results are not particularly sensitive to the algorithm used.