A port depends extensively on the capacity of its hinterland connections to handle cargo volumes. Port congestion impacts the availability of hinterland transport assets, such as drayage and rail. Furthermore, the availability of chassis to transport containers by road could face shortages and reduce capacity, as occurred on the West Coast of the United States. Chassis are also used for container storage at some rail yards and distribution facilities; a shortage of these chassis negatively impacted wheeled intermodal rail yard operations. A decline in the velocity of hinterland transportation ties up chassis assets, further impairing inland transport capacity.
Divergence was also observed between the increasing punctual and flexible requirements of supply chains, such as e-commerce, and the rigidity of a maritime shipping system driven by the economies of scale offered by post-Panamax ships. Often, the response to this situation has been to increase stocks and order additional quantities as a safeguard; in turn, this creates a backpropagating effect along supply chains, commonly known as the “bullwhip effect”. The demand surge effect, in part driven by actual demand, but also the outcome of artificial buffer stocking, stressed shipping resources, particularly containers. Container availability and shortages became the primary propagation and backpropagation mechanism along the maritime transport chain. In this context, containers were spending 20 per cent more time in the transport system with their immobilization on ships, chassis and container yards.