Horseshoe curve

This article is about engineering concept. For the landmark in Pennsylvania, see Horseshoe Curve (Pennsylvania). For other uses, see Horseshoe curve (disambiguation).

Horseshoe Curve (Pennsylvania)

The horse shoe shape gives the curve its name.

A horseshoe curve is a tight curve in a railway or a road, through an angle in excess of 180 degrees. A horseshoe curve is a means to lengthen the passage of an ascending or descending grade, so as to reduce the maximum gradient of ascent or descent. The horseshoe refers to the U shaped bypass of a straight route. The straight route would be too steep to climb, so instead the route takes a more circuitous route. In the case of roads, such curves, if tight enough, are typically called hairpin turns.

The route deviation thus undertaken greatly lengthens the actual distance travelled, and by so doing, it allows the difference in altitude to be averaged over a much longer track length. This is similar to the way a spiral works. However, a horseshoe curve does not involve the track crossing over itself, and the three main curves are only a part of a horseshoe, whereas a spiral is generally a continuous curvature. Another reason for a horseshoe curve is where the straight-ahead route involves bridging a deep gully. The deviation might allow the gully to be crossed at a more favourable location to one side.

Horseshoe curves are a common feature of railway lines in steeply graded or hilly country, where effective means have to be found to achieve an acceptable grade or construction cost of a line. Like spirals, the main limitation of the horseshoe is keeping the radius of the curvatures at or above a desirable minimum. Sharp curvatures will limit the speeds at which trains can run on a line.

Examples of horseshoe curves

America

• Cascade Tunnel has a gully on the western approaches that is an unnamed horseshoe curve.
• Chorro, California near San Luis Obispo.
• Dunsmuir, California has a pair of horseshoe curves nearby. Map
• Horseshoe Curve (Pennsylvania), at Kittanning Gap

Asia

• Kamaishi Line of East Japan Railway Company in Japan, has a horseshoe curve from Kamiarisu Station down to Rikuchū Ōhashi Station ("down" on the elevation and registration of direction of the line).

Australasia

• Picton railway station, New South Wales, turns back on itself at about 225 degrees.
• The Raurimu Spiral in New Zealand has a horseshoe curve as the first part of the climb.

Europe

• Dovrebanen, the main line of the Norwegian railway network, has a horseshoe from Dombås and up to the Dovre plateau.
• Flåmsbana, Norway, has a double horseshoe, one inside a tunnel, one in the open, few kilometres below top station.
• Grybów, Poland has a horseshoe curve 2,5 km west of the town.
• Kalisz, Poland has a double horseshoe curve leading the tracks from a flat plateau down to the valley of the Prosna river.
• Between Jelenia Góra and Szklarska Poręba in Poland there is a five-times, elongated horseshoe curve (50°51′19"N, 15°34′17"E). Map
• The Rhein-Ruhr S-Bahn in Germany has a horseshoe curve in Neviges, Velbert on the route between Essen and Wuppertal, known as the Prince William railway.

See also

• Hairpin turn