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The Seikan Tunnel (青函トンネル ''Seikan Tonneru'' or 青函隧道 ''Seikan Zuidō'') is a railway tunnel in Japan, with a long portion under the seabed. The track level is about below the seabed and below sea level.〔http://jr.hakodate.jp/global/english/train/tunnel/tunnel_omosiro.htm〕 It travels beneath the Tsugaru Strait—connecting Aomori Prefecture on the main Japanese island of Honshu with the northern island of Hokkaido—as part of the Kaikyo Line portion of the Hokkaido Railway Company (JR Hokkaido)'s Tsugaru-Kaikyō Line. The name ''Seikan'' comes from combining the ''on'yomi'' readings of the first characters of , the nearest major city on the Honshu side of the strait, and , the nearest major city on the Hokkaido side. The Seikan Tunnel is the deepest operational main-line rail tunnel in the world (though Guangzhou Metro Line 3's central tunnel has been longer since 2010) and the second longest after the Gotthard Base Tunnel in Switzerland. While the Seikan Tunnel is also the longest undersea tunnel in the world, the Channel Tunnel between the United Kingdom and France has a longer undersea portion.〔http://www.popularmechanics.com/science/extreme_machines/4217338.html?series=23〕 ==History== Connecting the islands Honshu and Hokkaido by a fixed link had been considered since the Taishō period (1912–1925), but serious surveying commenced only in 1946, induced by the loss of overseas territory at the end of World War II and the need to accommodate returnees. In 1954, five ferries, including the ''Toya Maru'', sank in the Tsugaru Strait during a typhoon, killing 1,430 passengers. The following year, Japanese National Railways (JNR) expedited the tunnel investigation.〔 Also of concern was the increasing traffic between the two islands. A booming economy saw traffic levels on the JNR-operated Seikan (a contraction of principal cities Aomori and Hakodate〔) Ferry use doubled to 4,040,000 passengers/year from 1955 to 1965, and cargo levels rose 1.7 times to 6,240,000 tonnes/year. In 1971, traffic forecasts predicted increasing growth that would outstrip the ability of the ferry pier facility, which was constrained by geographical conditions. In September 1971, the decision was made to commence work on the tunnel. A Shinkansen-capable cross section was selected, with plans to extend the Shinkansen network.〔 Arduous construction in difficult geological conditions proceeded. 34 workers were killed during construction. On 27 January 1983, Japanese Prime Minister Yasuhiro Nakasone pressed a switch that set off a blast that completed the pilot tunnel. Similarly on 10 March 1985, Minister of Transport Tokuo Yamashita symbolically bored through the main tunnel.〔 The success of the project was questioned at the time, as the 1971 traffic predictions were overestimates. Instead of the traffic rate increasing as predicted to a peak in 1985, it peaked earlier in 1978 and then proceeded to decrease. The decrease was attributed to the slowdown in Japan's economy since the first oil crisis in 1973 and to advances made in air transport facilities and longer-range sea transport. The tunnel was opened on 13 March 1988, having cost a total of ¥538.4 billion (US$3.6 billion) to construct. Once the tunnel was completed, all railway transport between Honshu and Hokkaido used it. However, for passenger transport, 90% of people use air due to the speed and cost. For example, to travel between Tokyo and Sapporo by train takes more than nine hours, with several transfers. By air, the journey is three hours and thirty minutes, including airport access times. Deregulation and competition in Japanese domestic air travel has brought down prices on the Tokyo-Sapporo route, making rail more expensive in comparison.〔 The ''Hokutosei'' overnight train service began after the completion of the Seikan Tunnel. The newer and more luxurious ''Cassiopeia'' overnight train service is often fully booked. Shinkansen trains will run through the tunnel once the first stage of the Hokkaido Shinkansen to Shin-Hakodate Station in Hakodate commences service in March 2016. The trains used on this service will connect Tokyo and Hakodate in four hours ten minutes, at a maximum speed of within the tunnel and outside it. The final stage is proposed to open to Sapporo Station in 2035 and is proposed to shorten the Tokyo-Sapporo rail journey to five hours. The Hokkaido Shinkansen will be operated by JR Hokkaido. 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「Seikan Tunnel」の詳細全文を読む スポンサード リンク
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