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{{Short description|
{{Use dmy dates|date=June 2021}}
{{BridgeTypePix
A '''viaduct''' is a specific type of bridge that consists of a series of arches, [[pier (architecture)|pier]]s or [[column]]s supporting a long elevated railway or road. Typically a viaduct connects two points of roughly equal elevation, allowing direct [[overpass]] across a wide valley, road, river, or other low-lying [[terrain]] features and obstacles.<ref name="oxf">{{cite web|url=https://www.oed.com/|title=viaduct – Definition of viaduct in English by Oxford English Dictionary|website=OED|access-date=21 September 2020}}</ref><ref name="mer-web">{{cite web|url=http://www.merriam-webster.com/dictionary/viaduct|title=Definition of VIADUCT|website=www.merriam-webster.com|access-date=27 March 2018}}</ref> The term ''viaduct'' is derived from the [[Latin]] ''via'' meaning "road", and ''ducere'' meaning "to lead". It is a 19th-century derivation from an [[analogy]] with [[Ancient Rome|ancient Roman]] [[aqueduct (bridge)|aqueducts]].<ref name="oxf"/> Like the [[Roman aqueduct]]s, many early viaducts comprised a series of arches of roughly equal length.▼
|image=Laighmilton1.JPG
|image_title=The 1812 [[Laigh Milton Viaduct]] in Ayrshire – the oldest surviving railway bridge in Scotland
|sibling_names=[[Aqueduct (bridge)|Aqueduct]]
|descendent_names=None
|ancestor_names=[[Trestle bridge]], [[Box girder bridge]]|carries=[[Controlled-access highway|Expressways]], highways, streets, railways
|span_range=Short (multiple)
|material=[[reinforced concrete]], [[prestressed concrete]], [[masonry]]
|movable=No
|design=medium
|falsework=available for use, since viaducts are all composed of low bridges.
}}▼
▲A '''viaduct''' is a specific type of [[bridge]] that consists of a series of arches, [[
==Over land==
[[File:Ouse Valley Viaduct 02.jpg|thumb|left|upright=1.1|The [[Ouse Valley Viaduct]] in Sussex, England]]
The longest in [[ancient history|antiquity]] may have been the [[Pont Serme]] which crossed wide marshes in southern France.<ref>Colin O’Connor: Roman Bridges, Cambridge University Press 1993, {{ISBN|0-521-39326-4}}, p. 99</ref> At its longest point, it measured 2,679 meters with a width of 22 meters.▼
▲The longest viaduct in [[ancient history|antiquity]] may have been the [[Pont Serme]] which crossed wide marshes in southern France.<ref>Colin O’Connor: Roman Bridges, Cambridge University Press 1993, {{ISBN|0-521-39326-4}}, p. 99</ref> At its longest point, it measured 2,679 meters with a width of 22 meters.
Viaducts are commonly used in many cities that are railroad [[transport hub|hub]]s, such as Chicago, [[Atlanta]], Birmingham, London and [[Manchester]]. These viaducts cross the large [[railroad yard]]s that are needed for [[freight train]]s there, and also cross the multi-track railroad lines that are needed for heavy rail traffic. These viaducts provide [[grade separation]] and keep highway and city street traffic from having to be continually interrupted by the train traffic. Likewise, some viaducts carry railroads over large valleys, or they carry railroads over cities with many cross-streets and avenues.▼
▲Viaducts are commonly used in many cities that are railroad [[transport hub|hub]]s, such as Chicago
[[File:Viaduct near Slade, Plymouth - Nicholas Matthew Condy - 60 1937 1.jpg|thumb|Viaduct near Slade, Plymouth, painting by [[Nicholas Matthews Condy|Nicholas Matthew Condy]]]]
Many viaducts over land connect points of similar height in a landscape, usually by bridging a river valley or other eroded opening in an otherwise flat area. Often such valleys had roads descending either side (with a small bridge over the river, where necessary) that become inadequate for the traffic load, necessitating a viaduct for "through" traffic.<ref>Brownlee, Christy (March 2005) "Taking the high road: France's new bridge helps a small town dodge traffic—and set a new world record" ''SuperScience'' 16(6): pp.12–15;</ref> Such bridges also lend themselves for use by rail traffic, which requires straighter and flatter routes.<ref>Davidsen, Judith (April 1993) "A new "lite" rail viaduct formula: Norman Foster designs a rapid-transit viaduct for Rennes, France" ''Architectural Record'' 181(4): p.26;</ref> Some viaducts have more than one deck, such that one deck has vehicular traffic and another deck carries rail traffic. One example of this is the [[Prince Edward Viaduct]] in Toronto, Canada, that carries motor traffic on the top deck as [[Bloor Street]], and metro as the [[Bloor–Danforth line|Bloor-Danforth]] [[Toronto subway|subway line]] on the lower deck, over the steep [[Don River (Ontario)|Don River]] [[Toronto ravine system|valley]]. Others were built to span settled areas, crossing over roads beneath—the reason for many viaducts in London.
==Over water==
[[File:
Viaducts over water make use of islands or successive arches. They are often combined with other types of bridges or tunnels to cross navigable waters as viaduct sections, while less expensive to design and build than tunnels or bridges with larger spans, typically lack sufficient horizontal and vertical clearance for large ships. See the [[Chesapeake Bay Bridge-Tunnel]].
The [[Millau Viaduct]] is a cable-stayed road-bridge that spans the valley of the river [[Tarn (river)|Tarn]] near [[Millau]] in southern France. It opened in 2004 and is the tallest vehicular bridge in the world, with one pier's summit at 343 metres (1,125 ft). The viaduct [[Danyang–Kunshan Grand Bridge]] in China was the [[List of longest bridges in the world|longest bridge in the world]] {{as of|2011|lc=y}}.<ref>[
==Land use below viaducts==
[[File:Deansgate Locks - geograph.org.uk - 1352312.jpg|thumb|"Deansgate Locks" bars under [[Deansgate-Castlefield Metrolink station|Deansgate Metrolink station]] in Manchester.]]
Where a viaduct is built across land rather than water, the space below the arches may be used for businesses such as car parking, vehicle repairs, light industry, bars and nightclubs. In the United Kingdom, many railway lines in urban areas have been constructed on viaducts, and so the infrastructure owner [[Network Rail]] has an extensive property portfolio in arches under viaducts.<ref>{{cite web| url = http://property.networkrail.co.uk/industrialunitstolet.aspx|
==Past and future==
[[Elevated highway|Elevated expressways]] were built in major cities such as [[Boston]] ([[Central Artery]]), Los Angeles, San Francisco, [[Seoul]], Tokyo and [[Toronto]] ([[Gardiner Expressway]]).<ref>{{cite web|url=http://www.tac-atc.ca/english/resourcecentre/readingroom/conference/conf2003/pdfs/gadiner.pdf|title=Toronto built, then demolished an expressway|website=tac-atc.ca|access-date=27 March 2018|archive-date=6 July 2011|archive-url=https://web.archive.org/web/20110706204817/http://www.tac-atc.ca/english/resourcecentre/readingroom/conference/conf2003/pdfs/gadiner.pdf|url-status=dead}}</ref> Some were demolished because they were unappealing and divided the city.{{Citation needed|date=March 2011}} In other cases, viaducts were demolished because they were structurally unsafe, such as the [[California State Route 480|Embarcadero Freeway]] in San Francisco, which was damaged
Other uses have been found for some viaducts. In Paris, France, a repurposed rail viaduct provides a garden promenade on top and workspace for artisans below. The garden promenade is called the [[Coulée verte René-Dumont]] while the workspaces in the arches below are the [[Viaduc des Arts]]. The project was inaugurated in 1993. Manhattan's [[High Line]], inaugurated in 2009, also uses an elevated train line as a linear [[urban park]].
In Indonesia viaducts are used for railways in [[Java]] and also for highways such as the [[Jakarta Inner Ring Road]]. The [[Coulée verte René-Dumont]] in Paris, France is a disused viaduct which was converted to an [[urban park]] in 1993. In January 2019 the [[Alaskan Way Viaduct]] in Seattle was closed and replaced with a [[Alaskan Way Viaduct replacement tunnel|tunnel]] after several decades of use due to being seismically unsafe.{{citation needed|date=July 2021}}▼
▲In Indonesia viaducts are used for railways in [[Java]] and also for highways such as the [[Jakarta Inner Ring Road]]
[[File:P1060258 Paris XII boulevard Daumesnil arcades rwk.JPG|thumb|center|The [[Viaduc des Arts]], Paris, France. ]]
==See also==
{{Portal|Transport|Engineering|Architecture}}
* [[Causeway]]
* [[Crueize Viaduct]]
* [[Flying junction]]
* [[List of bridge types]]
▲| wikt=Viaduct
▲}}
==References==
{{Reflist|22em}}
== External links ==
* {{Commons category inline|Viaducts}}
* {{Wiktionary inline|Viaduct}}
{{Bridge footer}}
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