Double traversals in optimal picker routes for warehouses with multiple blocks

Order picking involves collecting items from their locations within a warehouse. Existing algorithms for finding minimal picker routes consider limited options for travel within a subaisle. One action, traversing a subaisle twice, is not required in rectangular warehouses with two cross-aisles, however, is necessary for larger warehouses. In this work, we demonstrate that double traversals are not required to connect cross-aisle travel regardless of warehouse size. This result simplifies the structure of feasible tours, enabling more efficient algorithms.