Track transition curve: Difference between revisions

Revision as of 11:57, 18 March 2018

Revision as of 12:42, 18 March 2018

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A '''track transition curve''', or '''spiral easement''', is a mathematically-calculated curve on a section of highway, or [[track (rail transport)|railroad track]], in which a straight section changes into a curve. It is designed to prevent sudden changes in [[centripetal acceleration|lateral (or centripetal) acceleration]]. In plane (viewed from above), the start of the transition of the horizontal curve is at infinite radius, and at the end of the transition, it has the same radius as the curve itself and so forms a very broad spiral. At the same time, in the vertical plane, the outside of the curve is gradually raised until the correct degree of [[cant (road/rail)|bank]] is reached.

If such an easement were not applied, the lateral acceleration of a rail vehicle would change abruptly at one poinpoint (the [[tangent|tangent point]] where the straight track meets the curve), with undesirable results. With a road vehicle, the driver naturally applies the steering alteration in a gradual manner, and the curve is designed to permit that by using the same principle.

==History==