Publication Date


Document Type


Committee Members

Frank Ciarallo (Other), Pratik Parikh (Advisor), Xinhui Zhang (Other)

Degree Name

Master of Science in Engineering (MSEgr)


Many companies use distribution centers (DC) as hubs for storing and distributing products to customers (e.g., wholesalers, retailers, or consumers). Order picking, a critical activity in every DC, refers to retrieving products from the storage locations to fulfill customer orders. It accounts for over 50% of the DC operating cost. Order picking system design involves several decisions, such as layout of the picking area, storage policy, picking method, material handling equipment, and information technology, to name a few. Aisle configuration (number, length, width, and orientation) is a critical layout decision as it directly affects picker productivity and required space. Previous research in picking system layout optimization has focused on number and orientation of picking aisles, but not on the selection of an appropriate aisle-width (wide or narrow). Wide aisles require more space, but experience less congestion; in contrast, narrow aisles require less space, but may induce congestion among pickers. Congestion leads to a reduction in picker productivity, thus increasing labor cost to satisfy required system throughput. Our focus in this research is in determining the optimal aisle-width by evaluating the cost (labor and space) tradeoffs between wide-aisle and narrow-aisle system configurations for both manual and semi-automated systems. We propose a cost-based optimization model and use previously developed travel-time and picker-blocking models in solving the optimization model. We account for several system parameters, such as space and labor costs, throughput, system size, number of aisles, storage levels, and items picked in a tour in our experimentation. Our results indicate a preference for wide-aisle systems when cost of labor and required throughput are high, while they indicate a preference for narrow-aisle systems when cost of space and number of storage locations are high.

Page Count


Department or Program

Department of Biomedical, Industrial & Human Factors Engineering

Year Degree Awarded