reverse curve

plural reverse curves

1. A curve to the left or right which immediately curves in the opposite direction, and which is basically S-shaped.

   Some slight alterations in alignment were necessary to provide the pier line and the station is approached by severe reverse curves in both directions.

   1959 November, G. H. Robin, “Railways to Helensburgh—a pre-electrification retrospect”, in Trains Illustrated, page 544

   2 more examples

   One driver told him that a fireman who did not know the route might easily go "over the side" between Corby and Harringworth, unless warned beforehand of the reverse curves; he himself, in his firing days, used to try so to plan his firing that it was unnecessary to add any more coal while passing over this stretch at speed.

   1945 July and August, “Notes and News: "A Nice Day's Work"”, in Railway Magazine, page 235

   Chambers's Technical Dictionary defines a reverse curve as "a curve composed of two arcs, of the same or different radii, with their centres on opposite sides of the curve." In other words, a reverse curve is an "S" curve.

   1947 September and October, “The Why and The Wherefore: Definition of a Reverse Curve”, in Railway Magazine, page 334