The is a railway tunnel on the

Jōetsu Shinkansen The is a high-speed shinkansen railway line connecting Tokyo and Niigata, Japan, via the Tōhoku Shinkansen, operated by the East Japan Railway Company (JR East). Despite its name, the line does not pass through the city of Joetsu or the hist ...

on the border of

Gunma Prefecture is a prefecture of Japan located in the Kantō region of Honshu. Gunma Prefecture has a population of 1,937,626 (1 October 2019) and has a geographic area of 6,362 km2 (2,456 sq mi). Gunma Prefecture borders Niigata Prefecture and Fukushima ...

and

Niigata Prefecture is a Prefectures of Japan, prefecture in the Chūbu region of Honshu of Japan. Niigata Prefecture has a population of 2,227,496 (1 July 2019) and is the List of Japanese prefectures by area, fifth-largest prefecture of Japan by geographic area ...

, Japan.

In 1978, the Dai-Shimizu tunnel was completed. This tunnel was dug for the Jōetsu Shinkansen that was to be completed in 1982. This tunnel was the world's longest railway tunnel at until the

Seikan Tunnel The Seikan Tunnel ( ja, 青函トンネル, or , ), is a dual-gauge railway tunnel in Japan, with a portion under the seabed of the Tsugaru Strait, which separates Aomori Prefecture on the main Japanese island of Honshu from the northern isla ...

was built. During the construction, a fire created a large amount of smoke in the tunnel, and 16 workers died from

carbon monoxide poisoning Carbon monoxide poisoning typically occurs from breathing in carbon monoxide (CO) at excessive levels. Symptoms are often described as "flu-like" and commonly include headache, dizziness, weakness, vomiting, chest pain, and confusion. Large e ...

. When this tunnel was completed, the travel time between Niigata and Tokyo went down to approximately one hour and forty minutes, three hours faster than using the

Jōetsu Line The is a major railway line in Japan, owned by the East Japan Railway Company (JR East). It connects Takasaki Station in Gunma Prefecture with Miyauchi Station in Niigata Prefecture, linking the northwestern Kanto region and the Sea of Japan ...

. Also, when this tunnel was built, natural water was found during construction, which is now sold in bottles.Website on water
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References

Railway tunnels in Japan Tunnels completed in 1982 1982 establishments in Japan {{Asia-tunnel-stub