Spiral bridge

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A pigtail bridge on Iron Mountain Road

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.

Pigtail bridge[edit]

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[edit]

Hastings Spiral Bridge, 1895

Many multi-storey car parks feature such a design as this.

Spiral bicycle bridges[edit]

The Nesciobrug over the Amsterdam-Rijnkanaal in Amsterdam

Spiral pedestrian bridges[edit]

  • 1998-2004, Glass Spiral Bridge, Millennium Place, Coventry, England

See also[edit]


  1. ^ J.W. Parker, The roads and railroads, vehicles, and modes of travelling, of ancient and modern countries, p. 154

External links[edit]