is a railroad

Rail transport in Japan

Rail transport in Japan is a major means of passenger transport, especially for mass and high-speed travel between major cities and for commuter transport in metropolitan areas.-Overview:...

 tunnel

Tunnel

A tunnel is an underground passageway, completely enclosed except for openings for egress, commonly at each end.A tunnel may be for foot or vehicular road traffic, for rail traffic, or for a canal. Some tunnels are aqueducts to supply water for consumption or for hydroelectric stations or are sewers...

 in Gunma

Gunma Prefecture

is a prefecture of Japan located in the northwest corner of the Kantō region on Honshu island. Its capital is Maebashi.- History :The remains of a Paleolithic man were found at Iwajuku, Gunma Prefecture, in the early 20th century and there is a public museum there.Japan was without horses until...

 and Niigata Prefecture

Niigata Prefecture

is a prefecture of Japan located on the island of Honshū on the coast of the Sea of Japan. The capital is the city of Niigata. The name "Niigata" literally means "new lagoon".- History :...

s of Japan

Japan

Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...

, operated by JR East Jōetsu Line

Joetsu Line

The is a major rail line in Japan. Part of the JR East system, it runs from Takasaki Station in Takasaki, Gunma Prefecture, to Miyauchi Station in Nagaoka, Niigata Prefecture, linking the northwestern Kantō region and the Sea of Japan coast of the Chūbu region...

. The name originates from the Shimizu mountain pass nearby. There are three tunnels near each other, which are the Shimizu Tunnel, the Shin-Shimizu Tunnel, and the Dai-Shimizu Tunnel

Daishimizu Tunnel

The is a railway tunnel on the Jōetsu Shinkansen on the border of Gunma Prefecture and Niigata Prefecture, 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 tunnel at 22,200 m...

.

Shimizu tunnel

The Shimizu tunnel is the oldest of the three, opened in 1931 after nine years of construction. The length of the tunnel is 9,702 m, and has a single track

Single track (rail)

A single track railway is where trains in both directions share the same track. Single track is normally used on lesser used rail lines, often branch lines, where the traffic density is not high enough to justify the cost of building double tracks....

. Because of technical difficulties at the time, a spiral

Spiral (railway)

A spiral is a technique employed by railways to ascend steep hills.A railway spiral rises on a steady curve until it has completed a loop, passing over itself as it gains height, allowing the railway to gain vertical elevation in a relatively short horizontal distance...

 was built, with a diameter of 800 m. This tunnel was the longest in Japan at the time.

The construction improved the journey time between Niigata and Tokyo

Tokyo

, ; officially , is one of the 47 prefectures of Japan. Tokyo is the capital of Japan, the center of the Greater Tokyo Area, and the largest metropolitan area of Japan. It is the seat of the Japanese government and the Imperial Palace, and the home of the Japanese Imperial Family...

, decreasing it by 4 hours since trains no longer needed to go through the Usui Pass

Usui Pass

The is a mountain pass that lies between Nagano and Gunma Prefectures in Japan. It has served as one of the major transportation routes in central Japan since at least the eighth century.- Road :...

. Because the tunnel was too long to be suitable for steam locomotives, the tracks in and around the tunnel were electrified from the beginning.

Shin-Shimizu tunnel

The Shin-Shimizu tunnel was made in 1967 to make the line double track

Double track

A double track railway usually involves running one track in each direction, compared to a single track railway where trains in both directions share the same track.- Overview :...

, because of a high demand of transportation on the Joetsu line. The tunnel is 13,500 m long.