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The Oslofjord Tunnel ((ノルウェー語:Oslofjordtunnelen)) is a subsea road tunnel which traverses the Oslofjord, connecting Hurum and Frogn in Norway. Carrying three lanes National Road 23, the long tunnel reaches a depth of below mean sea level. The tunnel has a maximum gradient of seven percent. It acts as the main link connecting Buskerud with Follo and Østfold, supplementing the Moss–Horten Ferry which runs further south. The crossing was originally served by the Drøbak–Storsand Ferry, which commenced in 1939. Plans for a fixed link were launched in 1963, originally based on two bridges which would connect to Håøya. Plans resurfaced in the early 1980s with the advent of subsea tunneling technology and the Oslo Airport location controversy, which proposed airports in Hurum, Ås and Hobøl. Even though Gardermoen was ultimately build as the airport, the tunnel had raised sufficient support to be built irrespectively. Parliament gave approval on 13 December 1996 and construction started on 14 April 1997. The tunnel was official opened on 29 June 2000 and was financed in part by a toll, collected by Bompengeselskapet Oslofjordtunnelen at a toll plaza in Frogn. The tunnel was flooded in 2003 and 2008 and experienced a landslide in 2003. All of these incidents resulted in the tunnel being closed for weeks. There have been two major truck fires, one in 2006 and one in 2011. After the latter incident, the tunnel has been closed for heavy traffic exceeding 7.5 tonnes. In an effort to eliminate the problem, the Public Roads Administration has proposed building a second tube. ==Specifications== The Oslofjord Tunnel is a long subsea tunnel which constitutes part of National Road 23 and is hence part of the Trans-European road network. The tunnel traverses below Drøbaksundet of the Oslofjord, reaching a maximum depth of below mean sea level. The tunnel has three lanes, with one used as a climbing lane in the uphill direction to overcome the seven percent gradient. It has a speed limit of , which is enforced by traffic enforcement cameras. The tunnel has a width of and was at the time of construction build after criteria for a traffic of up to 7,500 vehicles per day.〔Alteren (2004): 7〕 The tunnel is equipped with 25 evacuation rooms. These can be sealed off from the main tunnel and can each provide pressurized space for thirty to fifty people while a fire is being fought. There is a natural flow of of sea- and ground water into the tunnel every minute. To handle this a pump system is installed capable of draining per minute. There is a natural reservoir under the tunnel able to retain of water, which can act as a buffer. It can also be used as a water source for the fire department. The tunnel is built with continual concrete elements to ensure better protection against water leaks.〔 The structure has received artistic decorations in the form of gobo lighting. The tunnel is indefinitely closed for vehicles exceeding in length. From the onset it was designed to be expanded to two tubes, hence a second tube was designed to be built on the south side.〔Norwegian Public Roads Administration (2013): 5〕 National Road 23 is long and runs from the E18 at Kjellstad in Lier through the municipalities of Røyken and Hurum to the E6 at Vassum in Frogn. The section from Bjørnstad in Røyken to Vassum was built at the same time as the tunnel and is referred to as the Oslofjord Link (Norwegian: ). The crossing primarily serves as a quicker link connecting Buskerud to Follo and Østfold. Alternative crossing involve driving north via Oslo or south via the Moss–Horten Ferry.〔 The route saves and 30 minutes compared to driving via Oslo. The tunnel is owned and operated by the Norwegian Public Roads Administration. As part of a national road, its operation and maintenance is financed by the national government. Toll collection is carried out by Bompengeselskapet Oslofjordtunnelen AS, a limited company owned in equal shares by Akershus County Municipality and Buskerud County Municipality. They have subcontracted the operations of their administration and the toll plaza to Vegfinans. Undiscounted toll prices are NOK 60 for cars and NOK 130 for trucks (vehicles exceeding 3.5 tonnes). Payment is automated through Autopass. The tunnel experienced a traffic an average 4,432 vehicles per day in 2003. The average annual peak was reached at 7,138 in 2010, before falling to 6,827 in 2012. The road is owned and maintained by the Norwegian Public Roads Administration as a nationally financed project.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Oslofjord Tunnel」の詳細全文を読む スポンサード リンク
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