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. The shape of the bridge forms a helix, not a spiral.
In the Black Hills of South Dakota, 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 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 in the 1930s.
Spiral road bridges
- 1895-1951, the Spiral Bridge at Hastings High Bridge, Hastings, Minnesota
- 1904, the Wiadukt Stanisława Markiewicza in Ulica Karowa which connects Krakowskie Przedmiescie to river level, Warsaw, Poland
- 1930s, Three bridges on Iron Mountain Road
- One bridge on South Dakota Highway 87 in Wind Cave National Park
- 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
- The C-345 near Málaga, Spain
- New Clear Water Bay Road in New Kowloon, Hong Kong
- Rongqiao Road Spiral Bridge, Chongqing, China
- 1981, Kawazu-Nanadaru Loop Bridge, a double loop bridge in Kawazu, Japan ( )
- Mizukami Loop Bridge, in Mizukami, Kumamoto ( )
- 2004, the Nanpu Bridge interchange in Puxi, Shanghai, China
- Ma On Shan Bypass, in Ma On Shan, New Territories, Hong Kong
- The Thames Tunnel (1825-1843) was originally planned to have an underground spiral giving access to road traffic, but this was never built.
- Cahill Expressway, Sydney, New South Wales, Australia. Spiral turns left in order to turn right.
- Lincoln Tunnel, approach road to west portal, Weehawken, New Jersey, USA.
- Iron Mountain Road, Custer State Park, South Dakota, USA.
- Sa Calobra, Majorca, Spain ( )
- New Clear Water Bay Road, New Kowloon, Hong Kong ( )
- N8 Bypass Brienzwiler, Switzerland ( )
- Isenfluh, Switzerland.
- A6 Highway, Italy ( )
- Antirio to Lamia highway (E65), on the climb of Mount Parnassos to Delphi, Greece, there is a 270 degrees spiral using an overpass.
- Astoria–Megler Bridge, south approach.
- Yurikamome, approach to Rainbow Bridge from the mainland, Tokyo
- General Artigas Bridge from Colón, Entre Ríos, Argentina to Paysandú, Paysandú Department, Uruguay, across the Uruguay river. Cantilever bridge with a spiral on the Uruguay side.
Many multi-storey car parks feature such a design as this.
Spiral bicycle bridges
Spiral pedestrian bridges
- 1998-2004, Glass Spiral Bridge, Millennium Place, Coventry, England
- J.W. Parker, The roads and railroads, vehicles, and modes of travelling, of ancient and modern countries, p. 154
||This article includes a list of references, related reading or external links, but its sources remain unclear because it lacks inline citations. (November 2010)|
- Bernie Hunhoff, The Man Who Designed the Pigtails, South Dakota Magazine, 27 July 2006,
- Jim Pisarowicz, Pigtail Bridge, Wind Cave National Park, National Park Service
- Brochure, Welcome to the Peter Norbeck Scenic Byway, United States Forest Service
- Missouri River Bridges of South Dakota, 1920 to 1980, interview of Kenneth R. Scurr, Former South Dakota Bridge Engineer, by Emory Johnson, So. Dakota State University