Japan Railway & Transport Review No. 2 (Inside front cover & pp.43–45)

Bridges and tunnels linking the Japanese Archipelago

The four major islands of Japan became united in 1988, when the Kojima-Sakaide Route of the Honshu-Shikoku Bridges and the Seikan Tunnel between Honshu and Shikoku opened to traffic. These are the tunnels and bridges carrying the railways and roads between the four islands.
Honshu-Shikoku Bridges
The Honshu-Shikoku Bridges comprise three routes. Both the most-easterly Kobe-Naruto route and the most-westerly Onomichi-Imabari route are designed only for road traffic, but the Kojima-Sakaide route in the middle, a long chain of gigantic two-level bridges and viaducts opened in 1988, is for both rail and road traffic.

Photos: The Akashi Kaikyo Bridge of the Kobe- Naruto route, due to open in 1998 with a sixlane motorway, will be by far the world's longest suspension bridge with a centre span of 1.99 km.
(Honshu-Shikoku Bridge Authority)
Photos: Although only a double-track narrow-gauge railway is running at the moment, the structure is designed to carry another double track for a standard-gauge (shinkansen) to be built in the future.
(JR Shikoku & Geographical Survey Institute)
Photo: The total length of the double-deckbridges and viaducts of the Kojima-Sakaide route is 13.1 km, and the largest bridge is the Minami Bisan-Seto Bridge, a suspension bridge with a centre span of 1.1 km.
(Honshu-Shikoku Bridge Authority)

Kanmon Bridge and Tunnels
The Kanmon Strait between Honshu and Kyushu is a narrow and dangerous passage with fast tidal currents through which many merchant vessels sail. Train ferries used to cross the strait, but wartime Japan needed a safer means of carrying people and goods, and a 3.6- km single-track railway tunnel was completed in 1942 as the first fixed link.
Another single-track tunnel (3.6 km) was completed in 1944. After the war, a twolane road tunnel (3.46 km) was completed in 1958. The third link is a suspension bridge completed in 1973 with a centre span of 712 metres, carrying a six-lane motorway. Rapid economic growth brought the extension of the shinkansen network to Kyushu, and the double-track Shin-Kanmon Tunnel (18.7 km) was completed in 1975. Courtesy: Geographical Survey Institute

Map: Four fixed links crossing the Kanmon Strait: (left to right) the Kanmon Railway Tunnel, the Kanmon Motorway Bridge, the Kanmon Road Tunnel and the Shin-Kanmon Tunnel for shinkansen.
(Geographical Survey Institute)
Photo: The Kanmon Railway Tunnel: The undersea part comprises two separate single-track tunnels.
(JR Kyushu)
Photo: The Kanmon Bridge carrying a six-lane motorway.
(Japan Highway Public Corporation)
Photo: A Series 300 Nozomi super-express train leaving the Shin-Kanmon Tunnel.
(JR West)

Seikan Tunnel
The island of Hokkaido was Japan's frontier for a long time. People went there to open up new land and the island's rich natural resources were brought to the main island by sea. The Tsugaru Strait between Hokkaido and Honshu is a wide and stormy international waterway through which many ships, including naval vessels of Japan's neighbours, pass frequently. In 1954, the Toya-Maru, a train ferry sailing between Aomori and Hakodate, was hit by a severe typhoon and sank with 1,314 passengers (of whom only 159 survived). The disaster prompted thoughts of constructing a railway tunnel under the strait, and a series of serious studies were started.
The construction work started officially in 1964, and the tunnel was finally opened in 1988. The engineering works were extremely difficult and expensive because of bad geological conditions. The total length of the tunnel is 53.85 km including the 23.35 km under the sea. The main tunnel is designed to carry a double-track shinkansen line in future, although only narrow-gauge trains are running at present. The two undersea stations are mainly for emergency use, but tourists can enjoy a short guided visit. Courtesy: Asahi Shimbun

Photo: The Toya-Maru disaster (26 September 1954) prompted thoughts of building an undersea tunnel.
(Asahi Shimbun)
Map: (Geographical Survey Institute)
Figure: The 23.35km undersea part comprises three bores: a double-track railway tunnel, a parallel service tunnel, and a pilot tunnel now serving as a drainage tunnel.
Figure: In future, the main tunnel will be used for shinkansen traffic, too.
Photo: A train arriving at Tappi-Kaitei station at the Honshu undersea side of the tunnel.
(JR Hokkaido)
Photo: Huge halls behind the undersea station platforms are currently used for tourist exhibition. The halls will be used as shinkansen track maintenance depots in future.
(JR Hokkaido)