A logical step in cargo unitization and a large stride in terms of volume involved, is the system by which dumb barges or lighters, in other words barges without engines, empty or laden with goods, are carried as units aboard specialized deep sea ships.
Just like containers, these barges can be loaded adjacent to a user’s premises, being then towed via waterways to the port of embarkation before proceeding to their ultimate destination aboard a mothership. After off-loading, the barges once more have the facility to reach their destination by waterway under tow, whilst the mothership, with minimum delay, can return with other loaded or empty barges which are available.
The variety of goods these barges can carry is as varied as for containers, and they can equally convey containers themselves, their advantage being in the large loads of several hundred tonnes per barge.
Barge systems so far developed are known as either SeeBee, LASH (Lighter Aboard Ship) and BACAT (Barge Aboard Catamaran) each using a distinctive method of loading/discharging barges, and each system operating its own size of barge on particular trade routes.