Exact results for the order picking time distribution under return routing

This paper derives exact expressions for the Laplace-Stieltjes transform of order picking time in single- and 2-block warehouses. We consider manual warehouses that deploy return routing assume sizes follow a Poisson distribution. The results this apply to wide range storage policies, including but not restricted class-based random storage. Furthermore, we compare performance policies warehouse lay-outs by using numerical inversion transforms.