The order picking process, - the retrieval of products from specified locations according to customer orders, - is the most laborious and costly process in a warehouse. It consumes almost 60% of all warehouse labour activities. Various routing methods can lead to significant improvements. This chapter analyses the influence of routing methods on a picker travel distance in a wide-aisle warehouse. In order to determine potential travel distance savings, a simulation model was created. Routing methods in a wide-aisle warehouse and other order picking process optimisations are analysed through simulation. The presented results show that by using appropriate combination of optimisation methods, the picker travel distance can be reduced by about 60%.