Retarder (railroad)

In rail transport, a retarder is a device installed in a classification yard used to reduce the speed of freight cars as they are sorted into trains.


Each retarder consists of a series of stationary brakes surrounding a short section of each rail on the track that grip and slow the cars' wheels through friction as they roll through them.[1]

Computer control

Modern retarders are computer controlled to apply a precise amount of pressure on the wheels so that cars rolling down a yard's hump are slowed to a safe speed for coupling with cars already standing on the yard's tracks.[2]

Inert retarder

An inert retarder holds a cut of classified railcars to keep them from rolling out of a yard.[3]

See also


  1. "Safety at the Switches". Popular Science Monthly. New York: Popular Science Publishing Co. 107 (4): 38. October 1925.
  2. Boyd, Jim (2001). The American Freight Train. MBI Publishing. p. 63. ISBN 978-0-7603-0833-2.
  3. U.S. Federal Railroad Administration, Washington, D.C. (1983). "Definitions: Inert retarder." Railroad Noise Emission Compliance Regulations. Code of Federal Regulations, 49 C.F.R. 210.5.

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