Editing Tunnel (section)

== Variant tunnel types ==

=== Double-deck and multipurpose tunnels ===
[[File:San Francisco-Bay Bridge02.jpg|thumb|The upper-level traffic lanes through [[Yerba Buena Island]], part of the [[San Francisco–Oakland Bay Bridge]]]]
Some tunnels are double-deck, for example, the two major segments of the [[San Francisco–Oakland Bay Bridge]] (completed in 1936) are linked by a {{convert|540|foot|m|adj=mid|order=flip}} [[Yerba Buena Tunnel|double-deck tunnel]] section through [[Yerba Buena Island]], the largest-diameter bored tunnel in the world.<ref>{{cite web |date=4 November 2015 |title=San Francisco-Oakland Bay Bridge |url=http://mtc.ca.gov/about-mtc/what-mtc/bay-area-toll-authority/san-francisco-oakland-bay-bridge |archive-url=https://web.archive.org/web/20161107072916/http://mtc.ca.gov/about-mtc/what-mtc/bay-area-toll-authority/san-francisco-oakland-bay-bridge |archive-date=2016-11-07 |access-date=2024-01-23 |work=Bay Area Toll Authority}}</ref> At construction this was a combination bidirectional rail and truck pathway on the lower deck with automobiles above, now converted to one-way road vehicle traffic on each deck.

In Turkey, the [[Eurasia Tunnel]] under the [[Bosphorus]], opened in 2016, has at its core a {{convert|5.4|km|mile|abbr=on}} two-deck road tunnel with two lanes on each deck.<ref name="uc">{{cite web |title=Eurasia Tunnel Project |url=http://events.unicredit-cib.eu/uploads/media/Presentation_Basar_Arioglu_Yapi_Merkezi_Insaat.pdf |url-status=unfit |archive-url=https://web.archive.org/web/20160120170635/http://events.unicredit-cib.eu/uploads/media/Presentation_Basar_Arioglu_Yapi_Merkezi_Insaat.pdf |archive-date=20 January 2016 |access-date=13 April 2014 |publisher=[[Unicredit]] – Yapı Merkezi, SK EC Joint Venture}}</ref>

Additionally, in 2015 the Turkish government announced that it will build ''three''-level tunnel, also under the Bosporus.<ref>{{cite web |date=2015-02-27 |title=Istanbul's mega-project: World's first three-level tunnel to be built under the Bosporus – Daily Sabah |url=https://www.dailysabah.com/business/2015/02/27/istanbuls-megaproject-worlds-first-threelevel-tunnel-to-be-built-under-the-bosporus |url-status=live |archive-url=https://web.archive.org/web/20170219015521/https://www.dailysabah.com/business/2015/02/27/istanbuls-megaproject-worlds-first-threelevel-tunnel-to-be-built-under-the-bosporus |archive-date=19 February 2017 |access-date=2024-01-23 |website=[[Daily Sabah]]}}</ref> The tunnel is intended to carry both the Istanbul metro and a two-level highway, over a length of {{convert|6.5|km|mile|abbr=on}}.

The French {{ill|A86 Duplex Tunnel|fr|Duplex A86}} in west Paris consists of two bored tunnel tubes, the eastern one of which has two levels for light motorized vehicles, over a length of {{convert|10|km|mile|abbr=on}}. Although each level offers a physical height of {{convert|2.54|m|foot|abbr=on}}, only traffic up to {{convert|2|m|foot|abbr=on}} tall is allowed in this tunnel tube, and motorcyclists are directed to the other tube. Each level was built with a three-lane roadway, but only two lanes per level are used – the third serves as a hard shoulder within the tunnel. The A86 Duplex is Europe's longest double-deck tunnel.

In [[Shanghai]], China, a {{convert|2.8|km|mile|abbr=on}} two-tube double-deck tunnel was built starting in 2002. In each tube of the {{ill|Fuxing Road Tunnel|zh|复兴东路隧道}} both decks are for motor vehicles. In each direction, only cars and taxis travel on the {{convert|2.6|m|foot|abbr=on}} high two-lane upper deck, and heavier vehicles, like trucks and buses, as well as cars, may use the {{convert|4.0|m|foot|abbr=on}} high single-lane lower level.<ref>{{cite web |date=2002-11-01 |title=Shanghai to Dig Double-deck Tunnel |url=http://www.china.org.cn/english/China/47409.htm |url-status=live |archive-url=https://web.archive.org/web/20060515033120/http://www.china.org.cn/english/China/47409.htm |archive-date=15 May 2006 |access-date=2024-01-23 |website=China Facts and Figures 2002}}</ref>

In the Netherlands, a {{convert|2.3|km|mile|abbr=on}} two-storey, eight-lane, cut-and-cover road tunnel under the city of [[Maastricht]] was opened in 2016.<ref>{{cite web |last=Kalus |first=Ruben |date=2016-12-22 |title=Maastricht's new highway tunnel: a role model for Europe |url=http://www.dw.com/en/maastrichts-new-highway-tunnel-a-role-model-for-europe/av-36867098 |access-date=2024-01-23 |website=DW.COM}}</ref> Each level accommodates a full height, two by two-lane highway. The two lower tubes of the tunnel carry the [[A2 motorway (Netherlands)|A2 motorway]], which originates in Amsterdam, through the city; and the two upper tubes take the N2 regional highway for local traffic.<ref>{{Cite web |date=2015-08-17 |title=Unique stacked tunnel under Maastricht - Division Traffic & Infra |url=http://imtech.com/EN/traffic-infra/Traffic-Infra-Newsroom/Divisie-Imtech-Traffic-Infra-Homepage-Newsroom-Highlights/Unique-stacked-tunnel-under-Maastricht.html |url-status=dead |archive-url=https://web.archive.org/web/20150817110627/http://imtech.com/EN/traffic-infra/Traffic-Infra-Newsroom/Divisie-Imtech-Traffic-Infra-Homepage-Newsroom-Highlights/Unique-stacked-tunnel-under-Maastricht.html |archive-date=2015-08-17 |access-date=2024-01-23 |website=Imtech}}</ref>

The [[Alaskan Way Viaduct replacement tunnel]], is a $3.3&nbsp;billion {{convert|1.76|mi|adj=on|order=flip}}, double-decker bored highway tunnel under [[Downtown Seattle]]. Construction began in July 2013 using "[[Bertha (tunnel boring machine)|Bertha]]", at the time the world's largest [[earth pressure balance]] tunnel boring machine, with a {{convert|57.5|ft|adj=on|order=flip}} cutterhead diameter. After several delays, tunnel boring was completed in April 2017, and the tunnel opened to traffic on 4 February 2019.

[[New York City]]'s [[63rd Street Tunnel]] under the [[East River]], between the boroughs of [[Manhattan]] and [[Queens]], was intended to carry [[New York City Subway|subway]] trains on the upper level and [[Long Island Rail Road]] commuter trains on the lower level. Construction started in 1969,<ref>{{cite news|title=To Break Ground For 63rd St., East River Tunnel|url=http://fultonhistory.com/highlighter/highlight-for-xml?altUrl=http%3A%2F%2Ffultonhistory.com%2FNewspapers%252023%2FForest%2520Parkway%2520NY%2520Leader%2520Observer%2FForest%2520Parkway%2520NY%2520Leader%2520Observer%25201969-1971%2FForest%2520Parkway%2520NY%2520Leader%2520Observer%25201969-1971%2520-%25200628.pdf&highlightsFile=http%3A%2F%2Ffultonhistory.com%2Fhighlighter%2Fhits%2F816c7feba198b14dee5deb0dc12d134f#page=1|access-date=29 July 2016|work=New York Leader-Observer|via=[[Old Fulton New York Postcards]]|date=20 November 1969|page=8}}</ref> and the two sides of the tunnel were bored through in 1972.<ref>{{Cite news |date=11 October 1972 |title=Governor Rockefeller and Mayor Lindsay Attend 'Holing Through' of 63d St. Tunnel |url=https://www.nytimes.com/1972/10/11/archives/governor-rockefeller-and-mayor-lindsay-attend-holing-through-of-63d.html |url-access=subscription |access-date=3 February 2018 |work=The New York Times |pages=47 |language=en-US |issn=0362-4331}}</ref> The upper level, used by the [[63rd Street lines|IND 63rd Street Line]] ({{NYCS trains|63rd IND}}) of the New York City Subway, was not opened for passenger service until 1989.<ref>{{cite news |last=Lorch |first=Donatella |date=29 October 1989 |title=The 'Subway to Nowhere' Now Goes Somewhere |url=https://www.nytimes.com/1989/10/29/nyregion/the-subway-to-nowhere-now-goes-somewhere.html |url-access=subscription |access-date=20 October 2011 |newspaper=The New York Times |pages=1.37}}</ref> The lower level, intended for commuter rail, saw passenger service after completion of the [[East Side Access]] project, in late 2022.<ref>{{Cite web |date=2023-10-05 |title=East Side Access |url=https://new.mta.info/project/east-side-access |access-date=2024-01-23 |website=MTA |language=en}}</ref>

In the UK, the 1934 [[Queensway Tunnel]] under the [[River Mersey]] between [[Liverpool]] and [[Birkenhead]] was originally to have road vehicles running on the upper deck and trams on the lower. During construction the tram usage was cancelled. The lower section is only used for cables, pipes and emergency accident refuge enclosures.

Hong Kong's [[Lion Rock Tunnel]], built in the mid 1960s, connecting [[New Kowloon]] and [[Sha Tin New Town|Sha Tin]], carries a motorway but also serves as an [[Aqueduct (water supply)|aqueduct]], featuring a gallery containing five water mains lines with diameters between {{cvt|1.2|and|1.5|m|ft|0}} below the road section of the tunnel.<ref>{{cite web|url=https://www.waterworld.com/technologies/pipes/article/16216777/black-veatch-uses-trenchless-technology-for-water-main-rehabilitation-in-hong-kong|title=Black & Veatch uses trenchless technology for water main rehabilitation in Hong Kong – WaterWorld|date=5 June 2017|url-status=live|archive-url=https://web.archive.org/web/20170605114200/http://www.waterworld.com/articles/2009/08/black--veatch-uses.html|archive-date=5 June 2017}}</ref>

[[Wuhan]]'s Yangtze River Highway and Railway Tunnel is a {{cvt|2.59|km|mi}} two-tube double-deck tunnel under the [[Yangtze|Yangtze River]] completed in 2018. Each tube carries three lanes of local traffic on the top deck with one track [[Wuhan Metro]] [[Line 7 (Wuhan Metro)|Line 7]] on the lower deck.<ref>{{Cite web|title=新闻分析：这条隧道藏了多少科技秘密——揭秘"万里长江公铁第一隧"-新华网|url=http://www.xinhuanet.com/2018-10/01/c_129964700.htm|archive-url=https://web.archive.org/web/20190716063606/http://www.xinhuanet.com/2018-10/01/c_129964700.htm|url-status=dead|archive-date=16 July 2019|access-date=7 June 2020|website=www.xinhuanet.com}}</ref><ref>{{Cite web|last=汉网|date=27 September 2018|title=揭秘武汉长江公铁第一隧"尖板眼" 68个通道可供江底逃生|url=https://news.sina.com.cn/o/2018-09-27/doc-ifxeuwwr8734437.shtml|access-date=7 June 2020|website=news.sina.com.cn}}</ref><ref>{{Cite web|title=武汉长江公铁隧道工程打造全球"超级工程"样板-新华网|url=http://m.xinhuanet.com/hb/2018-09/19/c_1123450459.htm|access-date=7 June 2020|website=m.xinhuanet.com}}</ref>

[[Mount Baker Tunnel]] has three levels. The bottom level is to be used by [[Sound Transit]] light rail. The middle level is used by car traffic, and the top layer is for bicycle and pedestrian access.
 
Some tunnels have more than one purpose. The [[SMART Tunnel]] in [[Malaysia]] is the first multipurpose "''Stormwater Management And Road Tunnel''" in the world, created to convey both traffic and occasional [[flood]] waters in [[Kuala Lumpur]]. When necessary, floodwater is first diverted into a separate bypass tunnel located ''underneath'' the {{convert|2.5|mile|km|abbr=on|order=flip}} double-deck roadway tunnel. In this scenario, traffic continues normally. Only during heavy, prolonged rains when the threat of extreme flooding is high, the upper tunnel tube is closed off to vehicles and automated flood control gates are opened so that water can be diverted through both tunnels.<ref>{{cite web|url=https://www.mnn.com/green-tech/transportation/stories/drive-through-these-10-tremendous-tunnels|title=Drive through these 10 tremendous tunnels}}</ref>

=== Covered passageways ===
[[File:Sotetkapu.JPG|right|thumb|upright|The 19th century [[Dark Gate]] in [[Esztergom]], Hungary]]

Over-bridges can sometimes be built by covering a road or river or railway with [[brick]] or [[steel]] [[arch]]es, and then levelling the surface with earth. In railway parlance, a surface-level track which has been built or covered over is normally called a "covered way".

[[Snow shed]]s are a kind of artificial tunnel built to protect a railway from [[avalanche]]s of snow. Similarly the [[Stanwell Park]], [[New South Wales]] "steel tunnel", on the [[Illawarra railway line]], protects the line from rockfalls.

=== Underpass ===
{{main|Subway (crossing)}}
[[File:VIEW THROUGH CATTLEPASS NEAR BRIDAL VEIL FALLS. - Historic Columbia River Highway, Troutdale, Multnomah County, OR HAER ORE,26-TROUT.V,1-31.tif|right|thumb|Underpass for cattle created in 1914 construction of what is now [[Historic Columbia River Highway]]]]
An '''underpass''' is a road or railway or other passageway passing ''under'' another road or railway, under an [[overpass]]. This is not strictly a tunnel.

=== Utility Tunnel ===
A [[Utility tunnel|Utility Tunnel]] is built for the purpose of carrying one or more [[Public utility|utilities]] in the same space, for this reason they are also referred to as Multi-Utility Tunnels or MUTs. Through co-location of different utilities in one tunnel, organizations are able to reduce the financial and environmental costs of building and maintaining utilities.<ref>{{Cite journal |last1=Hunt |first1=D. V. L. |last2=Nash |first2=D. |last3=Rogers |first3=C. D. F. |date=2014-01-01 |title=Sustainable utility placement via Multi-Utility Tunnels |url=https://www.sciencedirect.com/science/article/pii/S0886779812000338 |journal=Tunnelling and Underground Space Technology |series=Underground Infrastructure Research 2012 |volume=39 |pages=15–26 |doi=10.1016/j.tust.2012.02.001 |bibcode=2014TUSTI..39...15H |issn=0886-7798}}</ref> These tunnels can be used for many types of utilities, routing steam, chilled water, electrical power or telecommunication cables, as well as connecting buildings for convenient passage of people and equipment.<ref name=":0" />