Intermodal freight transport involves the transportation of freight in a 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, may reduce damages and loss, and may allow freight to be transported faster. Reduced costs versus over road trucking is the key benefit for intracontinental use.
Intermodal transportation goes back to the 18th century and predates the railways. Some of the earliest containers were those used for coal shipping on the Bridgewater Canal in England in the 1780s. Coal containers (called 'loose boxes') were soon deployed on the early railways and used for road/rail transfers (road at the time being horse drawn).
Examples of wooden coal containers being used on railways go back to the 1830s on the Liverpool and Manchester Railway. In 1841 Isambard Kingdom Brunel introduced iron containers to move coal from the vale of Neath to Swansea Docks. By the outbreak of the First World War the Great Eastern Railway was using wooden containers to trans-ship passenger luggage between trains and sailings via the port of Harwich.
The early 1900s saw the first adoption of covered containers, primarily for the movement of furniture and intermodal between road and rail. A lack of standards limited the value of this service and this in turn drove standardisation. In the USA such containers, known as "lift vans', were in use from early as 1911.
In the United Kingdom containers were first standardised by the RCH Railway Clearing House in the 1920s, allowing both railway owned and privately owned vehicles to be carried on standard container flats. By modern standards these containers were small being five or ten foot long, normally wooden and with a curved roof and insufficient internal strength to stack. From 1928 the London, Midland and Scottish Railway offered 'door to door' intermodal road-rail services using these containers. This standard however failed to take off outside the United Kingdom.
Pallets made their first major appearance during World War II, when the United States military assembled freight on pallets, allowing fast transfer between warehouses, trucks, trains, ships, and aircraft. Because no freight handling was required, fewer personnel were required and loading times were decreased.
Truck trailers were first carried by railway before World War II, an arrangement often called "piggyback", by the small Class I railroad, the Chicago Great Western in 1936. The Canadian Pacific Railway was a pioneer in piggyback transport, becoming the first major North American railway to introduce the service in 1952. In the United Kingdom the big four railway companies offered services using standard RCH containers which could be craned on and off the back of trucks. Moving companies such as Pickfords offered private services in the same way.
It was not until the 1950s that containers started to revolutionize freight transportation. The United States Department of Defense produced specifications for standard containers for military use of by square cross section in units of ten foot long. The ISO International Organization for Standardization (ISO) issued standards based upon the US Department of Defense standards between 1968 and 1970, ensuring interchangeability between different modes of transportation worldwide. These rectangular stackable containers became known as ISO containers for this reason.
One pioneering railway was the White Pass and Yukon Route, who acquired the world's first container ship, the Clifford J. Rogers, built in 1955, and introduced containers to its railway in 1956. In the United Kingdom the modernisation plan and in turn the Beeching Report strongly pushed containerisation. The British Railways freightliner service was launched carrying 8' high pre-ISO containers. The older wooden containers and the pre-ISO containers were rapidly obsoleted by ten foot and twenty foot ISO standard containers, and as time went on by forty foot containers and larger.
In the United States of America, starting in the 1960s the use of containers increased steadily, with rail intermodal traffic tripling between 1980 and 2002 according to the Association of American Railroads (AAR), from 3.1 million trailers and containers to 9.3 million. Large investments were made in intermodal freight projects. An example was the $740,000,000 Port of Oakland intermodal rail facility begun in the late 1980s.
Since 1984, a mechanism for intermodal shipping known as double-stack rail transport has become increasingly common. Rising to the rate of nearly 70% of United States intermodal shipments, it transports more than one million containers per year. The double-stack rail car's unique design also significantly reduced damage in transit, and provided greater cargo security by cradling the lower containers so their doors cannot be opened. And a succession of large, new domestic container sizes was introduced to increase shipping productivity for customers. In Europe the more restricted loading gauge has limited the adoption of double-stack cars. However, in 2007 construction the Betuweroute was finished, a railway from Rotterdam to the German industrial heartland, which allows for double stacked containers. New Zealand has too large a number of low tunnels and bridges to make expansion economical.
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, consisting of a tank fitted inside a standard container frame, allows liquids to be carried. Refrigerated containers are used for perishables. There is also the swap body, which is typically used for road and rail transport, as they are 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.
Truck trailers are often used, in countries where the loading gauge is sufficient, 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.
Handling equipment can be designed with intermodality in mind, assisting with transferring containers between rail, road and sea. These can include:
In North America, containers are often shipped by rail in container well cars. These cars resemble flatcars but the newer ones have a container-sized depression, or well, in the middle (between the bogies or "trucks") of the car. This depression allows for sufficient clearance to allow two containers to be loaded in the car in a "double stack" arrangement. The newer container cars also are specifically built as a small articulated "unit", most commonly in components of three or five, whereby two components are connected by a single bogie as opposed to two bogies, one on each car (The photo above under "Equipment" shows an example of the new setup.) Double stacking is also used in parts of Australia. On some older railways, particularly in the United Kingdom, the use of well cars is necessary to carry single stacked large containers within the loading gauge.
It is also common in North America to transport semi-trailers on railway flatcars or spine cars, an arrangement called "piggyback" or TOFC (trailer on flatcar) to distinguish it from container on flatcar (COFC). Some flatcars are designed with collapsable trailer hitches so they can be used for trailer or container service. Such designs allow trailers to be rolled on from one end, though lifting trailers on and off flatcars by specialized loaders is more common. TOFC terminals typically have large areas for storing trailers pending loading or pickup.
A newer method of transporting trailers, the roadrailer, has been developed by RoadRailer Corporation, which is owned by the Norfolk Southern Railway. When the trailers are transported on rail, railway wheel assemblies are placed between the trailers, in effect turning the trailers into one large articulated railway car. This method is faster than carrying trailers on flatcars and requires no extra railway cars, but the trailers need to be specially designed (strengthened).
Container ships are used to transport containers by sea. These vessels are custom-built to hold containers. Some vessels can hold thousands of containers. Their capacity is often measured in TEU or FEU. These initials stand for "twenty-foot equivalent unit," and "forty-foot equivalent unit," respectively. For example, a vessel that can hold 1,000 40-foot containers or 2,000 20-foot containers can be said to have a capacity of . In the year 2005, the largest container ships in regular operation are registered to carry in excess of .
A key consideration in the size of container ships is that larger ships exceed the capacity of important sea routes such as the Panama and Suez canals. The largest size of container ship able to traverse the Panama canal is referred to as Panamax, which is presently around . A third set of locks is planned as part of the Panama Canal expansion project to accommodate container ships up to in future, comparable to the present Suezmax.
It costs about $8000 to ship a container from East Asia to North America when oil is at $100. As the price of oil increases, shipping costs increase.
Very large container ships also require specialized deepwater terminals. Available container fleet, route constraints, and terminal capacity plays a large role in shaping global container shipment logistics.