An analysis of dual-command operations in common warehouse designs

In a warehouse that uses dual-command operations, workers travel loaded from the pickup and deposit (P&D) point first to a location to store a pallet, then to a second location from which they pick a pallet and return to the P&D point. We develop expected travel distance expressions for such operations and use them to analyze three common warehouse designs. Our results indicate that the best of the three is - in our experience - the one least commonly found in practice. We also show that the optimal placement of a "middle cross aisle" in the most common design is, in fact, not in the middle.