Scheduling Logistics Activities in Staged Queues with Sequence-Dependent Changeover and Processing Times

Facilities for transportation, logistics and production often select entities for service from multiple queues in which a preparatory step is required before service can begin. The result is a staged queue with a restricted queuing discipline and sequence-dependent changeover and processing times. We present an efficient heuristic for scheduling operations to minimize average waiting times while fostering equity among users with different service requirements. With a two-queue system and two classes of arrival in each, we demonstrate how system performance can be improved relative to simpler scheduling rules such as FIFO or shortest processing and setup time. Then we apply the heuristic to a stochastic environment and present simulation results for a transportation system with this type of queuing structure.