Intermodal

Intermodal is a term that refers to more than one mode of transport. For example, passenger stations which provides transfers between buses and trains are described as intermodal. See: Intermodal passenger transport. This article describes intermodal as applied to the transportation of freight in a container or vehicle, using multiple modes of transportation (rail, ocean carrier and truck), without any handling of the freight itself when changing modes. The advantage of using containers is that it reduces cargo handling, and so improves security, reduces damages and loss, and allows freight to be transported faster.

History

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 aeroplanes. Because no freight handling was required, fewer personnel were required and loading times were decreased.

Truck trailers were first carried by railway after World War II, an arrangement often called "piggyback". The Canadian Pacific Railway was a pioneer in piggyback transport, becoming the first North American railway to introduce the service in 1952.

While rudimentary freight containers, then known as lift vans, were used in the United States as early as 1911, it was not until the 1950s that containers started to revolutionize freight transportation. 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. Starting in the 1960s the use of containers increased steadily. Standards for containers were issued by the International Organization for Standardization (ISO) between 1968 and 1970, ensuring interchangeability between different modes of transportation worldwide. The containers became known as ISO containers for this reason.

In the United States of America, rail intermodal traffic tripled between 1980 and 2002, according to the Association of American Railroads, from 3.1 million trailers and containers to 9.3 million.

Equipment

Containers, also known as intermodal containers or as ISO containers because the dimensions have been defined by the ISO, are the main type of equipment used in intermodal transport, particularly when one of the modes of transportation is by ship. Containers are eight feet wide by eight feet six inches high. Their length is usually either 20 feet, 40 feet, or 45 feet, although other lengths exist. They are made out of steel and can be stacked on top of each other. They can be carried by truck, rail, container ship, or aeroplane.

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, 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.

Truck trailers are often used for freight that is transported primarily by road and rail. Typically, regular trailers can be used, and do not need to be specially designed. When travelling by rail, trailers are transported on railway flatcars, an arrangement called "piggyback".

A newer method of transporting trailers has been developed by Road-Railer Corporation, which is owned by 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.

Vehicles

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 feet equivalent unit", and "forty feet 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 1,000 FEU or 2,000 TEU.

In North America, containers are often shipped by rail in well cars. These cars resemble flatcars but have a container-sized depression, or well, in the middle of the car. This depression allows for sufficient clearance to allow two containers to be loaded in the car, one on top of the other. In Europe, stricter railway height restrictions prohibit containers from being stacked two high, and containers are hauled one high either on standard flatcars or other rail cars.Template:Wiktionary