Spiral bridge

Hastings Spiral Bridge, 1895

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.

Spiral ramp to Nanpu Bridge in Shanghai, China

Pigtail bridge

A pigtail bridge on Iron Mountain Road

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

Name	Location	Year	Comment
A-7000 (previously C-345)	Málaga–Colmenar road, Spain		2 spiral tunnels at 36.775796°N 4.379339°W / 36.775796; -4.379339
A6 Highway	Italy		44.320409°N 8.377118°E / 44.320409; 8.377118
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, United States		Western terminus of US 30, a cross-country route from Atlantic City, New Jersey 46.187590°N 123.853260°W / 46.187590; -123.853260
Cahill Expressway	Sydney, Australia		Spiral turns left in order to turn right.
Caiyuanba Bridge South Approach	Chongqing, China		29.5360605°N 106.551513°E / 29.5360605; 106.551513
Canal Road Flyover	Victoria City, Hong Kong		22.2816003°N 114.1800447°E / 22.2816003; 114.1800447
Corkscrew Bridge, Old East Entrance Road, Yellowstone National Park (abandoned)	Wyoming, United States	1904, 1919	44.460000°N 110.117500°W / 44.460000; -110.117500
Eastern Harbour Crossing	Victoria City, Hong Kong		22.2886114°N 114.2126683°E / 22.2886114; 114.2126683
G329 South Bridge Approach	Shaoxing, China		30.0218999°N 120.7308062°E / 30.0218999; 120.7308062
G4011 Runyang Yangtze River Bridge Shiye Exit	Zhenjiang, China		32.2201231°N 119.3682047°E / 32.2201231; 119.3682047
General Artigas Bridge	Uruguay and Argentina		From Colón, Entre Ríos, Argentina, to Paysandú, Uruguay, across the Uruguay River. Cantilever bridge with a spiral on the Uruguay side. 32.265407°S 58.093289°W / -32.265407; -58.093289
Huanggang Port Approach	Shenzhen, China
Isenfluh	Bern, Switzerland		Loop entirely inside a 1.2 km tunnel 46.619905°N 7.898088°E / 46.619905; 7.898088
Jialing Jiahua Bridge Approach	Chongqing, China		29.5606004°N 106.5174331°E / 29.5606004; 106.5174331
Jinchang Road Bridge	Wuxi, China		Double loop bridge on each approach 31.556633°N 120.330889°E / 31.556633; 120.330889
Kawazu-Nanadaru Loop Bridge	Kawazu, Japan	1981	Double loop bridge. 34.791°N 138.938°E / 34.791; 138.938
Lincoln Tunnel Helix (New Jersey Route 495).	Weehawken, United States		40.767037°N 74.021383°W / 40.767037; -74.021383
Mizukami Loop Bridge	Mizukami, Kumamoto, Japan		32.315°N 131.01°E / 32.315; 131.01
N8 Bypass Brienzwiler	Switzerland		46.750521°N 8.108833°E / 46.750521; 8.108833
Nanpu Bridge Puxi Approach	Puxi, Shanghai, China	2004	31.208094°N 121.501765°E / 31.208094; 121.501765
Nansha Bridge Hai'ou Exit	Guangzhou, China		Interchange made of ramps from spiraling up to the Nansha Bridge. 22.889226°N 113.543465°E / 22.889226; 113.543465
New Clear Water Bay Road	New Kowloon, Hong Kong		22.331717°N 114.224617°E / 22.331717; 114.224617
Prefectural Road 53 Onawaba Bridge east approach	Gifu, Japan		35.423410°N 136.744817°E / 35.423410; 136.744817
Rongqiao Road Spiral Bridge	Chongqing, China		Triple Loop Bridge 29.5262731°N 106.5449174°E / 29.5262731; 106.5449174
Route de Cilaos	Réunion		21.181180°S 55.454704°E / -21.181180; 55.454704
S232 Bridge South Approach	Changzhou, China		31.715834°N 120.068168°E / 31.715834; 120.068168
Sa Calobra	Mallorca, Spain		39.831968°N 2.81574°E / 39.831968; 2.81574
Sembon Matsu Bridge Approaches	Osaka, Japan		Double loop bridge on each approach 34.6324803°N 135.4759645°E / 34.6324803; 135.4759645
Shinkizugawao Bridge North Approach	Osaka, Japan		The road turns 1180° (3.27 revolutions) (955° on the bridge deck + 180° on the abutment) 34.628474°N 135.463726°E / 34.628474; 135.463726
South Dakota Highway 87 in Wind Cave National Park	South Dakota, United States	1930s	43.601215°N 103.494340°W / 43.601215; -103.494340
SP99 just north of Bolzano	Italy		Two loops. One, involving a tunnel, is named Schneckentunnel, German for snail tunnel 46.510391°N 11.328084°E / 46.510391; 11.328084 46.512665°N 11.343147°E / 46.512665; 11.343147
Steinmen Crossing on Oregon Highway 273, part of Historical U.S. Highway 99 through the Siskiyou Mountains	Oregon, United States		42.092091°N 122.589541°W / 42.092091; -122.589541
Tianmen Shan Big Gate Road, Tianmen Mountain National Park (2 bridges)	Hunan, China		29.05424°N 110.48344°E / 29.05424; 110.48344 29.06547°N 110.48211°E / 29.06547; 110.48211
Tianxingzhou Yangtze River Bridge Tianxingzhou Exit	Wuhan, China		30.674541°N 114.387798°E / 30.674541; 114.387798
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		35.635036°N 83.466047°W / 35.635036; -83.466047
Three bridges on Iron Mountain Road/U.S. Route 16A	South Dakota, United States	1930s	Known locally as "pigtail bridges" From south to north: 43.861849°N 103.437623°W / 43.861849; -103.437623 43.869383°N 103.435572°W / 43.869383; -103.435572 43.874979°N 103.439530°W / 43.874979; -103.439530
U.S. Route 61 across Spiral Bridge at Hastings High Bridge	Hastings, United States	1895-1951	former location: Approximately 44.745137°N 92.853034°W / 44.745137; -92.853034
Weidun Road Bridge	Changzhou, China		31.722803°N 120.059752°E / 31.722803; 120.059752
Wiadukt Stanisława Markiewicza	Warsaw, Poland	1904	In Ulica Karowa which connects Krakowskie Przedmiescie to river level,
Yanbai Yellow River Bridge North Approach	Lanzhou, China		36.0789724°N 103.8814573°E / 36.0789724; 103.8814573
Yurikamome approach to Rainbow Bridge	Tokyo, Japan		From the mainland. 35.636712°N 139.756192°E / 35.636712; 139.756192
Zhoutouju Tunnel Approach	Guangzhou, China		23.0985181°N 113.2520531°E / 23.0985181; 113.2520531
Zuidweg Bridge	Zoetermeer, Netherlands		52.047468°N 4.475218°E / 52.047468; 4.475218
Lanhai Expressway descent	Lanzhou, China	2023	35.95°N 103.75°E / 35.95; 103.75
Hoàng Văn Thụ Bridge	Haiphong, Vietnam	2019	20°51′58.6″N 106°40′52.8″E

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

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.

See also

• Hairpin turn
• Spiral (railway)

Further reading

• 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