A retractable bridge is a type of

moveable bridge A moveable bridge, or movable bridge, is a bridge that moves to allow passage for boats or barges. In American English, the term is synonymous with , and the latter is the common term, but drawbridge can be limited to the narrower, historical ...

in which the deck can be rolled or slid backwards to open a gap while traffic crosses, usually a ship on a waterway. This type is sometimes referred to as a thrust bridge. Uppsala Ultunabron01 2005-06-16

Borden Avenue Bridge over Dutch Kills slide tracks jeh

Retractable bridges date back to medieval times. Due to the large dedicated area required for this type of bridge, this design is not common. A retractable design may be considered when the maximum horizontal clearance is required (for example, over a canal). Two remaining examples exist in New York City: the Carroll Street Bridge (built 1889) in

Brooklyn Brooklyn is a Boroughs of New York City, borough of New York City located at the westernmost end of Long Island in the New York (state), State of New York. Formerly an independent city, the borough is coextensive with Kings County, one of twelv ...

, and the Borden Avenue Bridge in

Queens Queens is the largest by area of the Boroughs of New York City, five boroughs of New York City, coextensive with Queens County, in the U.S. state of New York (state), New York. Located near the western end of Long Island, it is bordered by the ...

. A recent example can be found at Queen Alexandra Dock in

Cardiff Cardiff (; ) is the capital city, capital and List of urban areas in the United Kingdom, largest city of Wales. Cardiff had a population of in and forms a Principal areas of Wales, principal area officially known as the City and County of Ca ...

Wales Wales ( ) is a Countries of the United Kingdom, country that is part of the United Kingdom. It is bordered by the Irish Sea to the north and west, England to the England–Wales border, east, the Bristol Channel to the south, and the Celtic ...

, where the bridge is jacked upwards before being rolled on wheels. Helix Bridge at

Paddington Basin Paddington Basin is the name given to a long canal basin, and its surrounding area, in Paddington, London. The basin commences 500 m south of the junction known as Little Venice, of the Regent's Canal and the Paddington Arm of the Grand ...

in London is a more unusual example of the type, consisting of a glass shell supported in a helical steel frame, which rotates as it retracts. The Summer Street Bridge over Fort Point Channel in

Boston Boston is the capital and most populous city in the Commonwealth (U.S. state), Commonwealth of Massachusetts in the United States. The city serves as the cultural and Financial centre, financial center of New England, a region of the Northeas ...

is a variant type called a retractile bridge. This bridge is oriented northwest–southeast, with the northwest-bound lanes of traffic retracting diagonally to the north, and the southeast-bound lanes retracting diagonally to the west. However, the draws of this bridge have been fixed in place since 1959. Some retractable bridges are also floating bridges, such as the Hood Canal Bridge. Two other floating bridges in Washington state used to have retractable spans but were replaced with new floating bridges without retractable spans: the

Evergreen Point Floating Bridge The Evergreen Point Floating Bridge, also known as the 520 Bridge and officially the Governor Albert D. Rosellini Bridge, is a floating bridge that carries Washington State Route 520 across Lake Washington from Seattle to its eastern suburbs ...

(replaced in 2016) and Lacey V. Murrow Memorial Bridge (replaced after it accidentally sank in 1990). This design is popular in

Guyana Guyana, officially the Co-operative Republic of Guyana, is a country on the northern coast of South America, part of the historic British West Indies. entry "Guyana" Georgetown, Guyana, Georgetown is the capital of Guyana and is also the co ...

, which has the Demerara Harbour Bridge and the Berbice Bridge. Historical examples of designs for retractable bridges include those by

Leonardo da Vinci Leonardo di ser Piero da Vinci (15 April 1452 - 2 May 1519) was an Italian polymath of the High Renaissance who was active as a painter, draughtsman, engineer, scientist, theorist, sculptor, and architect. While his fame initially rested o ...

and

Agostino Ramelli Agostino Ramelli (1531–ca. 1610) was an Italian engineer best known for writing and illustrating the book of engineering designs ''Le diverse et artificiose machine del Capitano Agostino Ramelli'', which contains, among others, his desig ...

. In the

Netherlands , Terminology of the Low Countries, informally Holland, is a country in Northwestern Europe, with Caribbean Netherlands, overseas territories in the Caribbean. It is the largest of the four constituent countries of the Kingdom of the Nether ...

, especially in the province of

North Holland North Holland (, ) is a Provinces of the Netherlands, province of the Netherlands in the northwestern part of the country. It is located on the North Sea, north of South Holland and Utrecht (province), Utrecht, and west of Friesland and Flevola ...

, a

vlotbrug Vlotbrug (plural, ) translates from Dutch into English as "raft bridge". It is a special kind of floating retractable bridge, used at the Great North Holland Canal, which pivot either centrally or from one or both banks of a body of water to allow ...

is a design of retractable bridge across a

canal Canals or artificial waterways are waterways or engineered channels built for drainage management (e.g. flood control and irrigation) or for conveyancing water transport vehicles (e.g. water taxi). They carry free, calm surface ...

in which the roadway floats and can be retracted under fixed structures on the canal banks.

References

External links

Carroll Street Bridge history at bridgesnyc.com
{{Bridge footer Bridges by structural type Moveable bridges

See also

References

External links