Scheduling small number of quay cranes with non-interference constraint

Quay crane (QC) scheduling significantly affects the turn-around time of a container vessel, and it plays an important role in container terminal operation. Lee et al. (An approximation algorithm for quay crane scheduling with non-interference constraints in port container terminals, Presented at Tristan VI, Phuket, June 10–15, 2007 ) present a 2-approximation algorithm for QC scheduling problem with non-interference constraint. In this paper we revisit Lee’s heuristic for the scenario with small number of QCs, and prove that it is 4/3 and 5/3-approximation for the case with two QCs and the case with three QCs respectively.