characteristics. Stackers are used to add coal that arrives at the terminal to stockpiles in the yard and reclaimers are used to reclaim completed stockpiles for delivery to waiting ships at the berths.

We focus on the scheduling of the reclaimers. The stockyard motivating our investigation has four pads on which stockpiles are build. A stockpile takes up the entire width of a pad and a portion of its length. Each pad is served by two reclaimers that cannot pass each other and each reclaimer serves two pads, one on either side of the reclaimer. Effective reclaimer scheduling, even though only one of component of the management of the stockyard management at a coal terminal, is a critical component, because reclaimers tend to be the constraining entities in a coal terminal (reclaiming capacity, in terms of tonnes per hour, is substantially lower than stacking capacity).

In order to gain a better understanding of the challenges associated with reclaimer scheduling, we introduce an abstract model of reclaimer scheduling and study the complexity of different variants of the model as well as algorithms for the solution of these variants. Our investigation has not only resulted in insights that may be helpful in 