A hairpin turn (also hairpin bend or hairpin corner) is a bend in a road with a very acute inner angle, making it necessary for an oncoming vehicle to turn about 180° to continue on the road. It is named for its resemblance to a bent metal

hairpin A hairpin or hair pin is a long device used to hold a person's hair in place. It may be used simply to secure long hair out of the way for convenience or as part of an elaborate hairstyle or coiffure. The earliest evidence for dressing the ha ...

. Such turns in ramps and

trail A trail, also known as a path or track, is an unpaved lane or a small paved road (though it can also be a route along a navigable waterways) generally not intended for usage by motorized vehicles, usually passing through a natural area. Ho ...

s may be called switchbacks in

American English American English, sometimes called United States English or U.S. English, is the set of variety (linguistics), varieties of the English language native to the United States. English is the Languages of the United States, most widely spoken lang ...

, by analogy with switchback railways.

Description

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.

Highway A highway is any public or private road or other public way on land. It includes not just major roads, but also other public roads and rights of way. In the United States, it is also used as an equivalent term to controlled-access highway, or ...

s 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 limit Speed limits on road traffic, as used in most countries, set the legal maximum speed at which vehicles may travel on a given stretch of road. Speed limits are generally indicated on a traffic sign reflecting the maximum permitted speed, express ...

s, due to the sharpness of the turn. Highways of this style are also generally less costly to build and maintain than highways with

tunnel A tunnel is an underground or undersea passageway. It is dug through surrounding soil, earth or rock, or laid under water, and is usually completely enclosed except for the two portals common at each end, though there may be access and ve ...

s. On occasion, the road may loop completely, using a tunnel or bridge to cross itself at a different elevation (example on

Reunion Island Reunion may refer to: * Class reunion * Family reunion Reunion, Réunion, Re-union, Reunions or The Reunion may also refer to: Places * Réunion, a French overseas department and island in the Indian Ocean * Reunion, Commerce City, Colorado, U ...

: ; example near

Ashland, Oregon Ashland is a city in Jackson County, Oregon, United States. It lies along Interstate 5 in Oregon, Interstate 5 approximately 16 miles (26 km) north of the California border and near the south end of the Rogue Valley. The city's population w ...

). When this routing geometry is used for a rail line, it is called a

spiral In mathematics, a spiral is a curve which emanates from a point, moving further away as it revolves around the point. It is a subtype of whorled patterns, a broad group that also includes concentric objects. Two-dimensional A two-dimension ...

, or spiral loop. In

building, an alternative to switchbacks is the

stairway A stairwell or stair room is a room in a building where a stair is located, and is used to connect walkways between floors so that one can move in height. Collectively, a set of stairs and a stairwell is referred to as a staircase or stairway. ...

Notable hairpin turns

* * * * Fairmont Hairpin – hairpin bend at the

Fairmont Monte Carlo The Fairmont Monte Carlo is a resort hotel located in the Monte Carlo area of Monaco. It is managed by Fairmont Hotels and Resorts, a subsidiary of the Accor hospitality company. The hotel is situated beside the hairpin turn of the Circuit de Mon ...

on the

Circuit de Monaco Circuit de Monaco is a street circuit laid out on the city streets of Monte Carlo and La Condamine around the harbour of the Principality of Monaco. It is commonly, and even officially, referred to as "Monte Carlo" because it is largely inside ...

* Sitinjau Lauik - hairpin bend at the

Padang City Padang () is the capital and largest city of the Indonesian province of West Sumatra. It had a population of 833,562 at the 2010 CensusBiro Pusat Statistik, Jakarta, 2011. and 909,040 at the 2020 Census;Badan Pusat Statistik, Jakarta, 2021. the ...

and

Solok Solok (means ''valley'') is a city in West Sumatra, Indonesia. The motto of this city is Kota Beras which is an abbreviation of "Bersih, Elok, Rapi, Aman dan Sejahtera". It has an area of 58.72 km2 (0.14 percent of the area of West Sumatra ...

road. Part of national road and Sumatra highway

Railways

If a railway curves back on itself like a hairpin turn, it is called a horseshoe curve. The

Pennsylvania Railroad The Pennsylvania Railroad ( reporting mark PRR), legal name as the Pennsylvania Railroad Company, also known as the "Pennsy," was an American Class I railroad that was established in 1846 and headquartered in Philadelphia, Pennsylvania. At its ...

built one in

Blair County, Pennsylvania Blair County is a county in the Commonwealth of Pennsylvania. As of the 2020 census, the population was 122,822. Its county seat is Hollidaysburg, and its largest city is Altoona. The county was created on February 26, 1846, from parts of Hu ...

, which ascends the

Eastern Continental Divide The Eastern Continental Divide, Eastern Divide or Appalachian Divide is a drainage divide, hydrological divide in eastern North America that separates the easterly Atlantic Seaboard drainage basin, watershed from the westerly Gulf of Mexico wat ...

from the east. However, the

radius of curvature In differential geometry, the radius of curvature, , is the reciprocal of the curvature. For a curve, it equals the radius of the circular arc which best approximates the curve at that point. For surfaces, the radius of curvature is the radius ...

is much larger than that of a typical road hairpin. See this example at Zlatoust or

Hillclimbing Hillclimbing, also known as hill climbing, speed hillclimbing, or speed hill climbing, is a branch of motorsport in which drivers compete against the clock to complete an uphill course. It is one of the oldest forms of motorsport, since the firs ...

for other railway ascent methods.

Skiing

Sections known as hairpins are also found in the slalom discipline of

alpine skiing Alpine skiing, or downhill skiing, is the pastime of sliding down snow-covered slopes on skis with fixed-heel Ski binding, bindings, unlike other types of skiing (Cross-country skiing, cross-country, Telemark skiing, Telemark, or ski jumping) ...

. 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 Flush may refer to: Places * Flush, Kansas, a community in the United States Architecture, construction and manufacturing * Flush cut, a type of cut made with a French flush-cut saw or diagonal pliers * Flush deck, in naval architecture * F ...

References

External links