A U-shaped layout for manual order-picking systems

In manual order picking systems, order pickers walk or ride through a warehouse in order to collect items requested by customers. The performance of such a system is significantly dependent on its layout which determines the lengths of the order pickers’ tours and the corresponding picking times. Whereas for classic warehouse layouts all picking aisles are arranged in parallel to each other, in the warehouse layout presented here the picking aisles are arranged around a U-shaped central aisle. This layout has been developed for order picking systems in which slow-moving items are prevalent. A new routing strategy for such a warehouse is presented and an analytical expression for the expected tour length per picking order is derived. By comparing this estimation with those of routing schemes in classic warehouse layouts, it is demonstrated in which situations such U-shaped layouts allow for operating warehouses more efficiently.