Hairpin turn

Hairpin turn in Oregon, U.S. comparing with a type of hair pin (bobby pin).
24 zigs in Guizhou, China
Road D2204 ascends to the Col de Braus using hairpin bends in the Alpes Maritimes in the French Alps (43°51′58.0″N 7°22′50″E / 43.866111°N 7.38056°E / 43.866111; 7.38056)
Some of the 48 hairpin turns near the top of the northern ramp of the Stelvio Pass in Italy
Hairpin turn on Mont Ventoux in France
Hairpins on a track to the south of Mont Valier, Pyrenees

A hairpin turn (also hairpin bend, hairpin corner, etc.), named for its resemblance to a hairpin/bobby pin, is a bend in a road with a very acute inner angle, making it necessary for an oncoming vehicle to turn almost 180° to continue on the road. The hairpin turns are commonly seen in mountaineous area, and often appear continuously. Such turns in ramps and trails may be called switchbacks in American English, by analogy with switchback railways. In British English "switchback" is more likely to refer to a heavily undulating road—a use extended from the rollercoaster and the other type of switchback railway.

Description

The 270° bend on the Geiranger road (1882), known as "the Knot"

Hairpin turns are often built when a route climbs up or down a steep slope, so that it can travel mostly across the slope with only moderate steepness, and are often arrayed in a zigzag pattern. Highways with repeating hairpin turns allow easier, safer ascents and descents of mountainous terrain than a direct, steep climb and descent, at the price of greater distances of travel and usually lower speed limits, due to the sharpness of the turn. Highways of this style are also generally less costly to build and maintain than highways with tunnels.

On occasion, the road may loop completely, using a tunnel or bridge to cross itself at a different elevation (example on Reunion Island: 21°10′52″S 55°27′17″E / 21.18111°S 55.45472°E / -21.18111; 55.45472). When this routing geometry is used for a rail line, it is called a spiral, or spiral loop.

In trail building, an alternative to switchbacks is the stairway.

Roads with hairpin turns

Some roads with switchbacks (hairpin turns) include:

Europe

Map of spiral on Norwegian road 7 with Storegjeltunnelen and Dalbergtunnelen

United States

One of the most famous NASCAR tracks with hairpin turns was the old Riverside International Raceway in Riverside, California
WA 129 in Joseph Canyon

Mexico

Canada

Chile

Asia

Nujiang 72 turns/Baxoi 99 turns
Western Ghats, Kerala
Tribhuvan Highway, Nepal
Ancient 18 Hairpin Bends, known as Daha ata wanguwa on the way to/from Kandy/Mahiyanganaya

Australia

Motorsports

Fairmont Hotel Hairpin in Circuit de Monaco.
A WRC car taking a hairpin turn during 2007 Rallye Deutschland

Railways

If a railway curves back on itself like a hairpin turn, it is called a horseshoe curve. However, the radius of curvature is much larger than that of a typical road hairpin. See this example at Zlatoust[13] or Hillclimbing for other railway ascent methods.

Skiing

Sections known as hairpins are also found in the slalom discipline of alpine skiing. A hairpin consists of two consecutive vertical or "closed gates" which must be negotiated very quickly. (Three or more consecutive closed gates are known as a flush.)

See also

References

Media related to Hairpin turns at Wikimedia Commons

This article is issued from Wikipedia - version of the 11/20/2016. The text is available under the Creative Commons Attribution/Share Alike but additional terms may apply for the media files.