Reverse curve

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MUTCD W1-4L.svg
Railroad reverse ("S") curve

In civil engineering, a reverse curve (or "S" curve) is a section of the horizontal alignment of a highway or railroad route in which a curve to the left or right is followed immediately by a curve in the opposite direction.[1][2]

On highways in the United States reverse curves are often announced by the posting of a W1-4L sign (left-right reverse curve) or a W1-4R sign (right-left reverse curve), as called for in the Manual on Uniform Traffic Control Devices.[3]

Reverse curves cause buffer-locking. On the Northeast Corridor in the USA, these also hinder the development of high-speed rail.[4]

See also


  1. ^ Mundrey (2000). Railway Track Engineering. McGraw-Hill Education. pp. 164–179. ISBN 9780074637241.
  2. ^ Harry Rubey (1956). Route Surveys and Construction. Macmillan Publishers. pp. 86–88.
  3. ^ Federal Highway Administration (1971). Manual on uniform traffic control devices for streets and highways. U.S. Government Printing Office. p. 67.
  4. ^ "Analysis: Long road ahead for improving Northeast Corridor speeds".