One-dimensional vehicle scheduling with a front-end depot and non-crossing constraints

This paper considers the scheduling problem of multiple vehicles executing a given set of jobs in parallel along a shared pathway. The job set consists of storage and retrieval tasks, transporting goods between a front-end depot and given storage locations on the line. Non-crossing constraints need to be applied to the vehicle movements. This problem setting is relevant when a train is loaded with containers by multiple straddle carriers on the landside of a container terminal. Other potential applications exist in multi-shuttle automated storage and retrieval systems and multi-stage production systems where items are transported by parallel hoists. We formalize the problem, analyze its computational complexity, and develop exact and heuristic solution procedures.