The Intractability of the Picker Routing Problem

The Picker Routing Problem (PRP), which consists in finding a minimum-length tour between a set of storage locations in a warehouse, is one of the most important problems in the warehousing logistics literature. Despite its popularity, the tractability of the PRP in conventional multi-block warehouses remains an open question. This technical note aims to fill this research gap by establishing that the PRP is strongly NP-hard.