Intercontinental and transoceanic fixed links
However, the improvement of the global shipping industry and advent of international air travel has reduced the demand for many intercontinental land connections.
A service road tunnel runs the entire length of the crossing, but is closed to general use and used only during emergencies and for maintenance.
[citation needed] Additionally, there was a short-lived proposal for an underground roundabout beneath the Isle of Man, connecting tunnels to Ireland, Scotland, and two to England.
Most travellers between Sweden and Germany, both by road and train, use the 160 km (99 mi) shorter route with a ferry over the Fehmarn Belt southwestwards towards Hamburg or southwards to Rostock.
A tunnel could be built between Sweden and Åland, about 50 km (30 mi) long, and 100–200 m (330–660 ft) deep, with the lowest depth around Märket, a little detour.
Ferry services link Finland to Estonia as well as overground rail and road routes via Saint Petersburg in Russia.
Finland and Estonia share close linguistic, cultural, economic and historical ties and proponents of what they call "Talsinki" (a portmanteau of the names of the two capitals) point to the Øresund region as an example of a cross-national metropolitan area linked by an underwater bridge-tunnel.
[15][16] There is a project of an underwater tunnel that will link Palau (in Sardinia) with the island of La Maddalena, crossing a 3 km stretch of sea.
[19][20] There were proposals to build a railway and highway bridge over the Adriatic sea to connect Italy and Croatia, from Ancona to Zadar following a 120 km route.
The idea was presented by the Roman architect Giorgio De Romanis, and also called for the creation of a special company "Il ponte sull'Adriatico Srl".
The bridge would be suspended above the sea at a height of between 30 and 70 meters, and would also allow the laying of pipes for water, oil and gas, as well as the accommodation of telecommunication cables.
Some sources considered the project as being more realistic than a bridge between Calabria and Sicily[23] The Boknafjord tunnel (main part of the Rogfast project) is under construction and will in 2033 be the world's longest and deepest undersea road tunnel, 26.7 kilometres (88,000 ft) long and reach 392 metres (1,286 ft) under sea level.
A causeway faces considerable political hurdles as the disruption of Israeli shipping access to the Red Sea was seen as a casus belli by Israel ahead of the Six-Day War.
Saudi Arabia considers to develop a 440 km tunnel across the Red Sea to link its industrial city of Jazan with Massawa's port in Eritrea.
First proposed in 1996,[46] the project has since been subject to a number of academic discussions and feasibility studies, including by the China Railway Engineering Corporation.
[citation needed] Shikoku and Kyushu are the only adjacent major Japanese islands not directly connected by a fixed link.
It had the support of Iran's Ports and Maritime Organisation managing director, Ali Akbar Safaei, and Iranian President Ebrahim Raisi, who expect the creation of a joint Qatar-Iran committee with the Emir of Qatar, Tamim bin Hamad Al Thani.
[65] The Saudis were exploring two options to build a 400 km tunnel or bridge to link Gwadar (in Pakistan) with Muscat (in Oman) at the mouth of Strait of Hormuz at one end.
The objective was to bypass its trade routes (including for oil supplies) with Iran and Qatar, because of the Iran–Saudi Arabia proxy conflict, also to extend the Chinese Belt and Road Initiative.
The Tōya Maru accident of 1954, in which a train ferry sank in a typhoon, killing over a thousand people, was a major factor in tilting the decision towards construction of the tunnel.
[75] A tunnel/bridge between the Australian mainland and the island of New Guinea, bridging the Torres Strait, is not considered economically feasible owing to the great distance.
Because of the extreme depth and soft seabed of the Georgia Strait, and the potential for seismic activity, a bridge or tunnel would face monumental engineering, safety, and environmental challenges at a prohibitive cost.
However, President Donald Trump reinstated many travel restrictions towards Cuba during his term, including prohibition of direct ferry services.
The main goal was to cut travel time to and from the small island town that is currently served by daily ferry runs.
The gap has been crossed by adventurers on bicycle, motorcycle, all-terrain vehicle, and foot, dealing with jungle, swamp, insects, kidnapping, and other hazards.
It is intended to unite the Isla Grande de Chiloé with the Chilean continental territory, in the Los Lagos Region.
[97] At the end of the 19th century, Argentine President Domingo Sarmiento presented the "Argirópolis" project; which included building railway bridges uniting both countries through the Martín García island.
Several land connection projects through the Río de la Plata were evaluated by the governments of Argentina and Uruguay (also Mercosur), with the objective of erecting a road for vehicular, rail or both types of transit.
[103] The proposed routes are a direct link from the US to Europe, or from the US, crossing Canada, Greenland, Iceland and the Faroe Islands, to the United Kingdom, using an underwater vacuum tube train.
[104][105] The Maritime Research Institute Netherlands (Marin), in 2019, tested a model trans-Atlantic underwater tunnel between the United States and Europe capable of supporting hyperloop.
