The is a railway line in Hokkaido operated by Hokkaido Railway Company (JR Hokkaido), between Oshamambe Station in Oshamambe and Iwamizawa Station in Iwamizawa, approximately paralleling the coast of Iburi Subprefecture. There also is a branch line within Muroran, between Higashi-muroran and Muroran Station.
The section between Shiraoi and Numanohata is the longest straight railway section in Japan.
On 19 November 2016, JR Hokkaido's president announced plans to rationalise the network by up to 1,237 km, or ~50% of the current network, including the proposed conversion to Third Sector operation of the Tomakomai - Iwamizawa section of the Muroran Main Line. However, if local governments do not come up with an agreement, the section may face closure.
Basic data
Operators, distances
Hokkaido Railway Company (Services and tracks) From Oshamambe to Iwamizawa: 211.0 km From Higashi-Muroran to Muroran: 7.0 km Japan Freight Railway Company (Services) From Oshamambe to Iwamizawa: 211.0 km Track: Double: 176.7 km From Oshamambe to Tōya: 41.5 km From Usu to Nagawa: 4.9 km From Mareppu to Mikawa: 118.2 km From Yuni to Kuriyama: 5.1 km From Muroran to Higashi-Muroran: 7.0 km Single: the remainder Electric supply: From Muroran, via Higashi-Muroran to Numanohata: 74.9 km (20,000 V AC) Other sections are not electrified. Block system: Automatic
Services
The section between Oshamambe and Numanohata is the part of the main link route between Sapporo and Hakodate. As such, the limited express trains Super Hokuto and Hokuto run between two cities once per 1 to 2 hours, as well as Suzuran between Sapporo and Muroran.
As for the local service, the line is roughly divided into four sections, namely the section between Oshamambe and Higashi-Muroran, between Higashi-Muroran and Muroran, between Higashi-Muroran and Tomakomai, and between Tomakomai and Iwamizawa. The last section was once an important freight route, but became a quiet local line after coal mines closed.
Former services
Prior to the opening of the Hokkaido Shinkansen, there were also sleeping car trains between Honshu and Hokkaido, such as the Hokutosei, Cassiopeia, Twilight Express, and Hamanasu.
Stations
Some local trains may skip Koboro (marked "◌").
Branch Line
Rolling stock
Local
KiHa 40 series DMUs
KiHa 143 DMUs (Oshamambe to Numanohata) KiHa 150 DMUs (Oshamambe to Tomakomai) 711 series EMUs (until 26 October 2012) 737 series EMUs (Tomakomai to Muroran, from spring 2023)
Limited express
Suzuran
785 series AC EMUs
789 series AC EMUs
Super Hokuto
KiHa 281 series DMUs
KiHa 261-1000 series DMUs
Hokuto
KiHa 183 series DMUs
History
In 1892, the Hokkaido Colliery and Railway Company opened the line from Muroran (now Higashi-Muroran) to Iwamizawa. The line was built to link coal mines in the Iwamizawa-Asahikawa region and Muroran Port. The line was extended to the current Muroran in 1897. The Japanese Government nationalised the Hokkaido Colliery Railway in 1906, and the Higashi-Muroran - Muroran section was double-tracked in 1910.
The section between Oshamambe and Higashi-Muroran was opened between 1923 and 1928 as the by the Imperial Japanese Government Railways, which later became the Japanese National Railways (JNR). The line was built to bypass the mountainous section of the Hakodate Main Line, as well as to link the inland Iburi to the Muroran Port. The two lines were merged into one in 1931, and renamed the Muroran Main Line, with the Higashi-Muroran - Muroran section becoming known as the branchline. In 1935, a rail motor service was established on the branchline.
Initially, the line mainly functioned as a freight line. However, with the reduction in coal being mined, from the 1960s the line's main traffic shifted to passengers. At present, all the intercity express trains between Sapporo and Hakodate operate over the Chitose and Muroran lines to Oshamambe, bypassing the north section of the Hakodate Main Line route.
The last steam locomotive hauled regular service ran between Iwamizawa and Muroran in 1975.
Duplication
Growing coal traffic on the Iwamizawa - Muroran section resulted in the double-tracking of the 101 km Higashi-Muroran - Mikawa section in stages between 1920 and 1958. The 7 km Iwamizawa - Shibun section was double-tracked in 1961, but returned to single track in 1994. The 9 km Yuni - Kurioka section was doubled between 1968 and 1969, but the 4 km Kuriyama - Kurioka section became single track in 1990 as a result of the collapse of a tunnel.