A spiral bridge, loop bridge, or pigtail bridge is a road bridge which loops over its own road, allowing the road to climb rapidly. This is useful in steep terrain, or where the approach road to a bridge would terminate too far from the bridge's end.

Pigtail bridge

In the Black Hills

Black Hills

The Black Hills are a small, isolated mountain range rising from the Great Plains of North America in western South Dakota and extending into Wyoming, USA. Set off from the main body of the Rocky Mountains, the region is something of a geological anomaly—accurately described as an "island of...

 of South Dakota

South Dakota

South Dakota is a state located in the Midwestern region of the United States. It is named after the Lakota and Dakota Sioux American Indian tribes. Once a part of Dakota Territory, South Dakota became a state on November 2, 1889. The state has an area of and an estimated population of just over...

, a particular form of spiral bridge, locally called a 'pigtail bridge' was introduced in 1932 by Cecil Clyde Gideon, the self-taught superintendent of Custer State Park

Custer State Park

Custer State Park is a state park and wildlife reserve in the Black Hills of southwestern South Dakota, USA. The park is South Dakota's largest and first state park, named after Lt...

 turned highway designer. He called them “spiral-jumpoffs”. During the planning for Iron Mountain Road, there was a need to negotiate sudden elevation drops while preserving natural features for this scenic highway; the corkscrew design allowed for a spectacular - although expensive - solution to this problem. In order to blend the bridges with their surroundings, natural materials such as local timber were used.

Most pigtail bridges were built by the Civilian Conservation Corps

Civilian Conservation Corps

The Civilian Conservation Corps was a public work relief program that operated from 1933 to 1942 in the United States for unemployed, unmarried men from relief families, ages 18–25. A part of the New Deal of President Franklin D...

 in the 1930s.

Spiral road bridges

• 1895-1951, the Spiral Bridge at Hastings High Bridge, Hastings, Minnesota
  Hastings, Minnesota
  Hastings is a city in Dakota counties in the U.S. state of Minnesota, near the confluence of the Mississippi and St. Croix Rivers. The population was 22,172 at the 2010 census. It is the county seat of Dakota County. The bulk of Hastings is in Dakota County; only a small part of the city extends...
  
  
• 1904, the Wiadukt Stanisława Markiewicza in Ulica Karowa which connects Krakowskie Przedmiescie
  Krakowskie Przedmiescie
  Krakowskie Przedmieście is one of the most impressive and prestigious streets of Poland's capital.Several other Polish cities also have streets named Krakowskie Przedmieście. In Lublin, it is the main and most elegant street...
  
   to river level, Warsaw
  Warsaw
  Warsaw is the capital and largest city of Poland. It is located on the Vistula River, roughly from the Baltic Sea and from the Carpathian Mountains. Its population in 2010 was estimated at 1,716,855 residents with a greater metropolitan area of 2,631,902 residents, making Warsaw the 10th most...
  
  , Poland
  Poland
  Poland , officially the Republic of Poland , is a country in Central Europe bordered by Germany to the west; the Czech Republic and Slovakia to the south; Ukraine, Belarus and Lithuania to the east; and the Baltic Sea and Kaliningrad Oblast, a Russian exclave, to the north...
  
  
• 1930s, Three bridges on Iron Mountain Road
• One bridge on South Dakota Highway 87
  South Dakota Highway 87
  South Dakota Highway 87 is a highway running through the Black Hills of the U.S. state of South Dakota. The road's northern terminus is U.S. Route 16 and U.S. Route 385 about south of Hill City. The road's southern terminus is U.S. Route 385 about east of Pringle, South Dakota, or north of Hot...
  
   in Wind Cave National Park
  Wind Cave National Park
  Wind Cave National Park is a United States national park north of the town of Hot Springs in western South Dakota. Established in 1903 by President Theodore Roosevelt, it was the seventh U.S. National Park and the first cave to be designated a national park anywhere in the world. The cave is...
  
  
• Steinmen Crossing on Oregon Highway 273, part of Historical U.S. Highway 99 through the Siskiyou Mountains.
• A bridge on US Highway 441 between Gatlinburg, Tennessee and Cherokee, North Carolina at Bearpen Hollow in the Great Smoky Mountains Nat'l Park
  Great Smoky Mountains
  The Great Smoky Mountains are a mountain range rising along the Tennessee–North Carolina border in the southeastern United States. They are a subrange of the Appalachian Mountains, and form part of the Blue Ridge Physiographic Province. The range is sometimes called the Smoky Mountains or the...
  
  
• The C-345 near Málaga, Spain
• New Clear Water Bay Road in New Kowloon
  New Kowloon
  New Kowloon is an area in Kowloon, Hong Kong, bounded in the south by Boundary Street, and in the north by the ranges of the Lion Rock, Beacon Hill, Tate's Cairn and Kowloon Peak...
  
  , Hong Kong
• Rongqiao Road Spiral Bridge, Chongqing
  Chongqing
  Chongqing is a major city in Southwest China and one of the five national central cities of China. Administratively, it is one of the PRC's four direct-controlled municipalities , and the only such municipality in inland China.The municipality was created on 14 March 1997, succeeding the...
  
  , China
• 1981, Kawazu-Nanadaru Loop Bridge, a double loop bridge in Kawazu
  Kawazu, Shizuoka
  is a town located on the east coast of Izu Peninsula in Kamo District, Shizuoka, Japan. As of February 2009, the town has an estimated population of 8,074 and a density of 80.1 persons per km². The total area is 100.79 km²...
  
  , Japan
• 2004, the Nanpu Bridge interchange in Puxi
  Puxi
  Puxi is the historic center of Shanghai, China, and remains the home of approximately 48% of Shanghai's residents in an area of 288 km². Puxi is distinguished from Pudong to its east, which is separated from it by the Huangpu River...
  
  , Shanghai
  Shanghai
  Shanghai is the largest city by population in China and the largest city proper in the world. It is one of the four province-level municipalities in the People's Republic of China, with a total population of over 23 million as of 2010...
  
  , China
• Ma On Shan Bypass, in Ma On Shan, New Territories
  New Territories
  New Territories is one of the three main regions of Hong Kong, alongside Hong Kong Island and the Kowloon Peninsula. It makes up 86.2% of Hong Kong's territory. Historically, it is the region described in The Convention for the Extension of Hong Kong Territory...
  
  , Hong Kong

Spiral bicycle bridges

The Nesciobrug over the Amsterdam-Rijnkanaal in Amsterdam

Amsterdam

Amsterdam is the largest city and the capital of the Netherlands. The current position of Amsterdam as capital city of the Kingdom of the Netherlands is governed by the constitution of August 24, 1815 and its successors. Amsterdam has a population of 783,364 within city limits, an urban population...

Spiral pedestrian bridges

• 1998-2004, Glass Spiral Bridge, Millennium Place, Coventry
  Coventry
  Coventry is a city and metropolitan borough in the county of West Midlands in England. Coventry is the 9th largest city in England and the 11th largest in the United Kingdom. It is also the second largest city in the English Midlands, after Birmingham, with a population of 300,848, although...
  
  , England