A spiral bridge, loop bridge, helix 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. Despite its name, the typical shape of a spiral bridge forms a helix, not a spiral.
Many multi-storey car parks feature such a design as this.
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—albeit 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.
List of spiral road bridges
|A-7000 (previously C-345)||Málaga-Colmenar road, Spain||2 spiral tunnels at|
|Antirio to Lamia highway (E65)||Greece||on the climb of Mount Parnassos to Delphi, Greece. 270° spiral using an overpass.|
|Astoria–Megler Bridge south approach (U.S. Route 101)||Astoria, Oregon, United States|
|Cahill Expressway||Sydney, New South Wales, Australia.||Spiral turns left in order to turn right.|
|Caiyuanba Bridge South Approach||Chongqing, China|
|Canal Road Flyover||Victoria City, Hong Kong|
|Corkscrew Bridge, Old East Entrance Road, Yellowstone National Park (abandoned)||Wyoming, United States||1904, 1919|
|Eastern Harbour Crossing||Victoria City, Hong Kong|
|G329 South Bridge Approach||Shaoxing, China|
|G4011 Runyang Yangtze River Bridge Shiye Exit||Zhenjiang, China|
|General Artigas Bridge||Uruguay and Argentina||From Colón, Entre Ríos, Argentina to Paysandú, Paysandú Department, Uruguay, across the Uruguay river. Cantilever bridge with a spiral on the Uruguay side.|
|Huanggang Port Approach||Shenzhen, China|
|Jialing Jiahua Bridge Approach||Chongqing, China|
|Jinchang Road Bridge||Wuxi, China||Double loop bridge on each approach|
|Kawazu-Nanadaru Loop Bridge||Kawazu, Japan||1981||Double loop bridge.|
|Lincoln Tunnel Helix
(New Jersey Route 495).
|Weehawken, New Jersey, United States|
|Mizukami Loop Bridge||Mizukami, Kumamoto, Japan|
|N8 Bypass Brienzwiler||Switzerland|
|Nanpu Bridge Puxi Approach||Puxi, Shanghai, China||2004|
|Nansha Bridge Hai'ou Exit||Guangzhou, China||Interchange made of ramps from spiraling up to the Nansha Bridge.|
|New Clear Water Bay Road||New Kowloon, Hong Kong|
|Prefectural Road 53 Onawaba Bridge east approach||Gifu, Japan|
|Rongqiao Road Spiral Bridge||Chongqing, China||Triple Loop Bridge|
|Route de Cilaos||Réunion|
|S232 Bridge South Approach||Changzhou, China|
|Sa Calobra||Majorca, Spain|
|Sembon Matsu Bridge Approaches||Osaka, Japan||Double loop bridge on each approach|
|Shinkizugawao Bridge North Approach||Osaka, Japan|
|South Dakota Highway 87 in Wind Cave National Park||South Dakota, United States||1930s|
|SP99 just north of Bolzano||Italy||Named Schneckentunnel, German for snail tunnel|
|Steinmen Crossing on Oregon Highway 273, part of Historical U.S. Highway 99 through the Siskiyou Mountains||Oregon, United States|
|Tianmen Shan Big Gate Road, Tianmen Mountain National Park (2 bridges)||Hunan, China|
|Tianxingzhou Yangtze River Bridge Tianxingzhou Exit||Wuhan, China|
|Thames Tunnel (planned, not constructed)||England||1825-1843||Originally planned to have an underground spiral giving access to road traffic, but this was never built.|
|The Loop Over Bridge, on U.S. Route 441 between Gatlinburg, Tennessee, and Cherokee, North Carolina, at Bearpen Hollow in the Great Smoky Mountains National Park||Tennessee, United States|
|Three bridges on Iron Mountain Road/U.S. Route 16A||South Dakota, United States||1930s||Known locally as "pigtail bridges"|
From south to north:
|U.S. Route 61 across Spiral Bridge at Hastings High Bridge||Hastings, Minnesota, United States||1895-1951||former location: Approximately|
|Weidun Road Bridge||Changzhou, China|
|Wiadukt Stanisława Markiewicza||Warsaw, Poland||1904||In Ulica Karowa which connects Krakowskie Przedmiescie to river level,|
|Yanbai Yellow River Bridge North Approach||Lanzhou, China|
|Yurikamome approach to Rainbow Bridge||Tokyo, Japan||From the mainland.|
|Zhoutouju Tunnel Approach||Guangzhou, China|
|Zuidweg Bridge||Zoetermeer, Netherlands|
Spiral bicycle bridges
- The bridge over the mainline and narrow-gauge railways just west of Wernigerode Hauptbahnhof station in the Harz, Germany has a spiral at each end
Spiral pedestrian bridges
- 1998–2004, Glass Spiral Bridge, Millennium Place, Coventry, England
Turnover bridges were a feature of some early British canals such as the Macclesfield. The boats were pulled by a horse, and in locations where the towpath crossed to the opposite bank, the spiral on one side allowed the horse to continue without detaching the tow rope. They were not universally provided as they were more expensive to build, needing to span both the canal and the towpath.
- Historic American Engineering Record (HAER) No. WY-86, "Corkscrew Bridge, Old East Entrance Road, Sylvan Pass, Lake, Teton County, WY"
- Historic American Engineering Record (HAER) No. SD-54, "Pigtail Bridge, Hot Springs, Fall River County, SD"
- J.W. Parker, The roads and railroads, vehicles, and modes of travelling, of ancient and modern countries, p. 154
- Historic American Engineering Record (HAER) No. TN-35-Q, "The Loop Over Bridge, Gatlinburg, Sevier County, TN"
- "Google Maps". Google Maps.
- 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, South Dakota State University