The flow of port containers

Containers that move through a container port are involved in four basic port activities:

(1) receiving, 

(2) loading/unloading,

(3) staging, 

and (4) storage. 

Import containers enter theport via a ship and leave by an inland carrier; export containers enter the port via an inland carrier and leave by ship. The receiving activity occurs when a container arrives at the port. Its arrival time and relevant information about the container, e.g., a description of its cargo, are recorded. The container will then be unloaded from the ship or vehicle and placed in the port’s storage area, where it will be retrieved in the future to be loaded on another ship or vehicle for departure from the port.

For an export container, staging is the activity of preparing the container to leave the port by ship. Specifically, the container is moved from storage to a staging location within the port to be with other containers that are waiting for the arrival of a ship onto which they will be loaded. Containers in the staging location are organized according to an optimal ship loading process, i.e., the ship’s stowage plan. The plan may be one that seeks to minimize the time in the loading/unloading of ship containers at the port and at future ports of call and to provide stability to the ship. Suppose an export container arrives at the port’s interchange gate by truck. Then, the truck moves to a location within the port, where the container is removed from the truck and placed in storage or at a staging location. If placed in a storage location, it will eventually be moved to a staging location to wait the arrival of the specific ship onto which it will be loaded. The ship on which an import container is stowed docks at a berth of the port. The con-tainer is unloaded from the ship by a ship-to-shore crane and placed on the port’s apron (the staging location). From the staging location, the container is moved to a storage location or loaded onto a truck for departure from the port. If placed in storage, it will eventually be removed by loading it onto a truck or rail car for departure from the port. The import  container will leave the port through its interchange gate. Containers may be stored on chassis or stacked in a storage location. A chassis is a trailer on which a container is carried when transported by a truck. Chassis storage is also referred to as an all-wheeled storage operation. Port chassis storage has a time advantage over stack storage for inland carriers and the port. Specifically, over-the-road truckers while in port do not have to wait for a container to be placed on a chassis as opposed to stack storage for departure from the port, since the container is already on a chassis. The time savings for inland carriers are also time savings for the port, since containers are in storage less time.  

A disadvantage of an all-wheeled storage operation is that it is land intensive. If port land is scarce and/or expensive, a port will likely utilize stack storage. Stack storage occurs at a given location in the port, where containers are stacked on top of each other. An advantage of stack storage is that containers require less space and thus less land for storage. The disadvantage of stack storage is the difficulty of retrieving and moving containers from and to the storage location, making stack storage more time intensive than having containers stored on chassis. Stack storage is also capital intensive, since it requires specialized yard equipment for stacking and unstacking containers.

In addition to import and export containers, a port’s containers may also be transshipment containers. A transshipment container is one that arrives at a port on one ship and is then transferred to another ship at the same port for departure, thereby not utilizing inland carriers. A port that handles transshipment containers is often referred to as a hub, main, or trans-shipment port. Such ports often have depth harbors that allow them to handle relatively large containerships (carrying large numbers of containers) that seek to call at a few ports so that they can spend more time at sea in order to take advantage of economies of ship size at sea. Examples of transshipment ports include Singapore, Hong Kong, and Shanghai. For the years 2000–2004, transshipment containers in Europe and the Mediterranean increased 58 percent (Penfold 2006).

Ports from which containers are transported on relatively small or feeder ships to and from main or transshipment ports are referred to as feeder ports. Containers destined to transshipment ports from feeder ports are export containers of the feeder ports but become transshipment containers of transshipment ports. Containers destined to feeder ports from transshipment ports are transshipment containers of transshipment ports but become import containers at feeder ports. Unlike non-transshipment ports, transshipment ports that handle only transshipment containers do not require inland interchange gates.