A container is a transport as well as a production unit and can move as an export, import or repositioning flow. Once a container has been unloaded, another transport leg must be found as moving an empty container is almost as costly as moving a full container. Shipping companies need containers to maintain their operations and level of service along the port network they call. Containers arriving in a market as imports must eventually leave, either empty or full. The longer the delay, the higher the cost. Repositioning thus begin immediately after a container has been unloaded and it is important since it involves costs that must be assumed by the shippers and are thus reflected by the costs paid by producers and consumers.