Feeder ships

To minimise the time they spend loading or discharging, big container ships usually call at only one or two large ports (known as ‘hubs’) at either end of their voyages. To serve smaller ports, which generate less traffic, are feeder ships. Much smaller than the ocean-going container vessels, these are built on the same principles, although occasionally they will have cranes or other equipment to handle containers themselves.

Barge carriers

An interesting variation on the unit-load concept which spawned the container ship is the barge carrier, or lighter-aboard-ship (LASH) vessel. Cargo is stowed in small enclosed barges rather than in containers. The barges are towed along waterways to a major port. The barge carrier usually has a hull which can be partly submerged aft by flooding tanks. This allows the barges to be floated in and secured, after which water is pumped out of the tanks and the hull resumes its normal height above the waterline.

The barge carrier takes much larger individual unit loads than container ships, and takes advantage of the economy with which barges can be moved along rivers and canals. However, it is viable only where there is a good network of navigable waterways to connect the factory or farm to the port, and from port to consumer, as for instance in the southern USA and in Northern Europe. This has meant a much less extensive network of services has developed than with containers.