Ann Oper Res DOI 10.1007/s10479-014-1665-8 Stochastic models for unit-load operations in warehouse systems with autonomous vehicles Debjit Roy · Ananth Krishnamurthy · Sunderesh Heragu · Charles Malmborg © Springer Science+Business Media New York 2014 Abstract This paper presents stochastic models for multi-tier warehouse systems that han- dle unit load transactions using autonomous vehicle-based technology. In this system, self- powered autonomous vehicles carry out unit-load transactions by moving along rails within a tier and using lifts or conveyors for vertical movement between tiers. We develop semi-open queuing network models to evaluate congestion effects in processing storage and retrieval transactions in this system. The queuing network is evaluated using a decomposition-based approach. The queuing model provides design insights on the effect of vehicle interference and vertical transfer mechanism on various system performance measures of interest. Insights from such studies can be especially useful during the conceptualization stage of warehouses that use autonomous vehicle technology. Keywords Autonomous vehicle technology · Vertical conveyors · Semi-open queuing network · Decomposition · Unit-load warehouses D. Roy Production and Quantitative Methods Area, Indian Institute of Management Ahmedabad, Gujarat 380015, India A. Krishnamurthy (B ) Department of Industrial and Systems Engineering, University of Wisconsin-Madison, Madison, WI 53706, USA e-mail: ananth@engr.wisc.edu S. Heragu Department of Industrial Engineering, University of Louisville, Louisville, KY 40292, USA C. Malmborg Department of Industrial and Systems Engineering, Rensselaer Polytechnic Institute, Troy, NY 12180, USA 123