Classification yard

A classification yard (American and Canadian English) or marshalling yard (British, Hong Kong, Indian, Australian and Canadian English) is a railway yard found at some freight train stations, used to separate railway cars on to one of several tracks. First the cars are taken to a track, sometimes called a lead or a drill. From there the cars are sent through a series of switches called a ladder onto the classification tracks. Larger yards tend to put the lead on an artificially built hill called a hump to use the force of gravity to propel the cars through the ladder.

Freight trains that consist of isolated cars must be made into trains and divided according to their destinations. Thus the cars must be shunted several times along their route in contrast to a unit train, which carries, for example, cars from the plant to a port, or coal from a mine to the power plant. This shunting is done partly at the starting and final destinations and partly (for long-distance-hauling) in classification yards.

Flat yards are constructed on flat ground, or on a gentle slope. Freight cars are pushed by a locomotive and coast to their required location.

Hump yards are the largest and most effective classification yards, with the largest shunting capacity, often several thousand cars a day. The heart of these yards is the hump—a lead track on a small hill over which an engine pushes the cars. Single cars, or a block of coupled cars, are uncoupled just before or at the crest of the hump, and roll by gravity onto their destination tracks in the tracks where the cars are sorted, called the classification bowl.

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