Open main menu

An undersea tunnel is a tunnel which is partly or wholly constructed under a body of water. They are often used where building a bridge or operating a ferry link is impossible, or to provide competition or relief for existing bridges or ferry links.[1]


Compared with bridgesEdit

One such advantage would be that a tunnel would still allow shipping to pass. A low bridge would need an opening or swing bridge to allow shipping to pass, which can cause traffic congestion. Conversely, a higher bridge that does allow shipping may be unsightly and opposed by the public. Higher bridges can also be more expensive than lower ones. Bridges can also be closed due to harsh weather such as high winds. Another possible advantage is space: the downward ramp leading to a tunnel may leave a smaller carbon footprint compared to the upward ramps required by most bridges.[citation needed]

Tunneling will generate soil that has been excavated and this can be used to create new land, as was done with the soil of the Channel Tunnel to create Samphire Hoe.

Further information: Tunnel – Choice of tunnels vs. bridges

Compared with ferry linksEdit

As with bridges, albeit with more chance, ferry links will also be closed during adverse weather. Strong winds or the tidal limits may also affect the workings of a ferry crossing. Travelling through a tunnel is significantly quicker than travelling using a ferry link, shown by the times for travelling through the Channel Tunnel (75–90 minutes for Ferry[2] and 21 minutes on the Eurostar). Ferries offer much less frequency and capacity[citation needed] and furthermore travel times tend to be longer with a ferry compared to a tunnel.


Compared with bridgesEdit

Tunnels require far higher costs of security and construction than bridges. This may mean that over short distances bridges may be preferred rather than tunnels (for example Dartford Crossing). As stated earlier, bridges may not allow shipping to pass, so solutions such as the Øresund Bridge have been constructed.

Compared with ferry linksEdit

As with bridges, ferry links are far cheaper to construct than tunnels, but not to operate. Also tunnels don't have the flexibility to be deployed over different routes as transport demand changes over time. Without the cost of a new ferry, the route over which a ferry provides transport can easily be changed.

List of notable examplesEdit

Tunnel Description Distance Depth (from surface) Constructed in
Thames Tunnel The oldest underwater tunnel in the world, crossing the Thames in London 0.4 km 1825–1843
Mersey Railway Tunnel Oldest and first longest underwater rail tunnels in the world, Crossing the Mersey in Liverpool 1.21 km 1881–1886
Severn Tunnel One of the oldest underwater tunnels in the world 7.01 km 1873–1886
Elbe Tunnel (1911) Pioneering underwater pedestrian and vehicular tunnel crossing the Elbe River in Hamburg, Germany 0.426 km 24 m 1907-1911
Holland Tunnel The first modern underwater road tunnel in the world, crossing the Hudson River between Manhattan and Jersey City 2.6 km 28.3 m 1920-1927
Queensway Tunnel The longest road tunnel of any type in the world when first built, crossing the River Mersey between Liverpool and Birkenhead 3.24 km 1925-1934
Bankhead Tunnel Carries Hwy. 90 in Mobile, AL. Business District, to Blakely Island. The eastern end has large "flood door" that can be closed to prevent water from the Mobile Bay from flooding the tunnel during hurricanes or tropical storms. Two lanes that only allows cars and pick up trucks now to travel through the tunnel. 1.033 km 12.2m 1938-1942
Lincoln Tunnel Set of road tunnels built in three stages, crossing the Hudson River between Manhattan and New Jersey 2.4 km average 30 m 1934-1957
Chesapeake Bay Bridge Tunnel Connecting Virginia Beach with the Eastern Shore of Virginia 1.6 km (tunnel section) 1960–1964
Raúl Uranga – Carlos Sylvestre Begnis Subfluvial Tunnel Formerly known as the Hernandarias Subfluvial Tunnel, is an underwater road tunnel that connects the provinces of Entre Ríos and Santa Fe in Argentina 2.4 km 32 m 1962-1969
Cross Harbour Tunnel A busy road tunnel in Hong Kong 1.86 km 1969–1972
Elbe Tunnel (1975) 8-lane road tunnel crossing the Elbe River in Hamburg, Germany 3.3 km 1968–1975
Ahmed Hamdi Tunnel Passes under Suez Canal connecting the Asian Sinai Peninsula to the town of Suez on the African mainland 1.63 km 1979–1981
Vardø Tunnel Connecting the small island community of Vardø in northern Norway to the mainland 2.9 km 88 m 1979–1982
Seikan Tunnel World's longest undersea railway tunnel when non-undersea portions of the tunnel are also measured 53.9 km 1971–1988
Sydney Harbour Tunnel 2.8 km 1988–1992
Channel Tunnel World's longest undersea portion railway tunnel 37.9 km 1988–1994
Hitra Tunnel The deepest in the world at the time of construction 5.6 km 264 m 1992–1994
Tokyo Bay Aqua-Line World's longest undersea portion road tunnel 9.6 km 1988–1997
North Cape Tunnel The tunnel goes under the Magerøysundet strait between the Norwegian mainland to the large island of Magerøya and the North Cape, Norway 6.8 km 212 m 1993–1999
Bømlafjord Tunnel The deepest point of the International E-road network. Connects Stord municipality to the Norwegian mainland. 7.8 km 260.4 m 1997–2000
Eiksund Tunnel World's deepest undersea road tunnel 7.7 km 287 m 2003–2008
Xiamen Xiang'an Tunnel 6.05 km 70 m 2005–2010
Qingdao Jiaozhou Bay tunnel 7.808 km 84.2 m 2006–2011
Xiamen Haicang Tunnel 6.306 km 73.6 m 2016–2020
Busan–Geoje Fixed Link World's deepest immersed road tunnel 3.7 km 48 m 2008–2010
Marmaray Rail tunnel connecting Asia and Europe in Istanbul 13.6 km 2004–2013
Marina Coastal Expressway Singapore's first undersea tunnel 5 km 2008–2013
Port of Miami Tunnel 2.1 km 2010–2014
Eurasia Tunnel Road tunnel connecting Asia and Europe in Istanbul 5.4 km 106 m 2011–2016
Transbay Tube Rail tunnel for Bay Area Rapid Transit. Connects Oakland to San Francisco. It is the longest underwater tunnel in North America. 5.8 km 41 m 1965-1969



  • Eysturoyartunnilin, Faroe Islands to be opened in 2020. The tunnel will have three entrances connected by an underwater roundabout. link The road length from Hvítanes to the roundabout will be 7.5 km, whilst the road length from the roundabout to Strendur and to Saltnes will be 1.7 km and 2.2 km, respectively. This results in an overall length of 11.24 km of sub sea tunnel.[3]
  • Ryfylke tunnel in Norway – to be opened in 2019, 14.3 km length, 292 m depth.
  • Rogfast tunnel in Norway – construction having started in 2018, at 27 km length, 392 m depth, it will be the longest road tunnel and deepest undersea tunnel in the world.


See alsoEdit