Intermodal freight transport involves the transportation of freight in an intermodal container or vehicle, using multiple modes of transportation (rail, ship, and truck), without any handling of the freight itself when changing modes. The method reduces cargo handling, and so improves security, reduces damages and losses, and allows freight to be transported faster. Reduced costs versus over road trucking is the key benefit for intracontinental use. The negative is that it takes longer than normal truck delivery would.
Containers, also known as intermodal containers or ISO containers because the dimensions have been defined by ISO, are the main type of equipment used in intermodal transport, particularly when one of the modes of transportation is by ship. Containers are 8-foot (2.4 m) wide by 8-foot (2.4 m) high. Since introduction, there have been moves to adopt other heights, such as 8-foot-6-inch (2.59 m), 9-foot-6-inch (2.90 m) and 10-foot-6-inch (3.20 m). The most common lengths are 20 feet (6.1 m) nominal or 19 feet (5.8 m) – 10+1⁄2 in (0.27 m) actual, 40 feet (12 m), 48 feet (15 m) and 53 feet (16 m), although other lengths exist. They are made of steel and can be stacked atop one another (a popular term for a two-high stack is “double stack”).
Onboard ships they are typically stacked up to seven units high. They can be carried by truck, rail, container ship, or aeroplane. When carried by rail, containers can be loaded on flatcars or in container well cars. In Europe, stricter railway height restrictions (smaller loading gauge and structure gauge) and overhead electrification prevent containers from being stacked two high, and containers are hauled one high either on standard flatcars or other railroad cars. Taller containers are often carried in well cars (not stacked) on older European railway routes where the loading gauge is particularly small.
Some variations on the standard container exist. Open-topped versions covered by a fabric curtain are used to transport larger loads. A container called a tanktainer, with a tank inside a standard container frame, carries liquids. Refrigerated containers are used for perishables. There is also the swap body, which is typically used for road and rail transport. Built too lightly to be stacked, they have folding legs under their frame so that they can be moved between trucks without using a crane.
Various non-standard container forms are commonly used. These include non-stackable open box containers, and several slightly non-standard geometries. European containers are often about two inches wider than the ISO standard although otherwise conformant, which can carry the euro-pallet standard pallet load. Specialised containers used in Europe include containerised coal carriers, and recently “bin-liners” – containers designed for the efficient road/rail transportation of rubbish from cities to recycling and dump sites.
In countries where the loading gauge is sufficient, truck trailers are often used for freight that is transported primarily by road and rail. Typically, regular semi-trailers can be used, and do not need to be specially designed.