Sekishō Line

The line grew out of an older coal railway, the Yūbari Line (夕張線). On 1 November 1892 the Hokkaido Colliery and Railway Company opened a branch of its Muroran line from Oiwake through Momijiyama (the later Shin-Yūbari) to Yūbari, built to develop the collieries of the Yūbari coalfield and to carry coal toward the Port of Muroran. The company was nationalised under the Railway Nationalization Act, its lines passing to the state railways on 1 October 1906, and in 1909 the Oiwake–Yūbari route was formally designated the Yūbari Line.

As coal traffic grew, the route was progressively double-tracked between 1912 and 1919. That capacity proved short-lived: after the parallel Yūbari Railway opened in 1930 and drained away traffic, the line was returned to single track in 1932, and the abandoned second formation and a disused tunnel north of Shimizusawa can still be traced today. The Yūbari Line is also remembered as one of the last places in Japan where steam locomotives hauled scheduled freight and worked shunting duties; the final steam-hauled freight ran on 24 December 1975, and the locomotive shed at Oiwake was destroyed by fire in April 1976.

The modern line took shape when, to give eastern Hokkaido a faster main route, the Japan Railway Construction Public Corporation built new lines at each end of the old Yūbari Line as a Class-C trunk railway. On 1 October 1981 the Chitose-Kūkō (now Minami-Chitose)–Oiwake section and the Shin-Yūbari–Kami-Ochiai Junction–Shintoku section opened, the Oiwake–Shin-Yūbari stretch of the old line was upgraded to become the middle of the route, and the whole was renamed the Sekishō Line; Momijiyama Station was renamed Shin-Yūbari at the same time. The remaining Shin-Yūbari–Yūbari stub became the line's Yūbari Branch. Previously travellers bound for Shintoku and points east had to go around by way of Asahikawa or Takikawa on the Nemuro Main Line; the new route cut the Sapporo–eastern-Hokkaido journey by roughly forty minutes, and limited expresses such as the Ōzora were rerouted over the Sekishō Line.

East of Shin-Yūbari the line drives through the Hidaka Mountains — the so-called backbone of Hokkaido — in a near-continuous chain of long tunnels, among them the 5,825-metre Shin-Noborikawa Tunnel, the longest mountain tunnel on any conventional line in Hokkaido. Across this stretch the only inhabited places are around Shimukappu and Tomamu, stations stand some twenty to thirty kilometres apart, and signal stations outnumber stations because many planned village stops were never needed once settlers left the land. On 1 April 1987 JR Hokkaido took over the whole line at the privatisation of Japanese National Railways, with JR Freight as a second operator. A high-speed upgrade completed on 22 March 1997 raised the line speed to 130 km/h and introduced the Super Ōzora limited express between Sapporo and Kushiro, though the maximum was later lowered to 120 km/h on 30 August 2014.

The line has seen two notable incidents. On 27 May 2011 a Super Ōzora service from Kushiro to Sapporo came to an emergency stop and caught fire inside the 685-metre No. 1 Niniu Tunnel near Shimukappu after a car derailed; all of the roughly 240 people aboard escaped, and 39 were taken to hospital, chiefly for smoke inhalation, with the line reopening on 30 May. On 16 February 2012 a northbound JR Freight train, held at a red signal at Higashi-Oiwake to let a Super Ōzora pass, failed to stop, ran through the catch points protecting the single track and struck the wall of a snow shelter; the diesel locomotive and four wagons derailed but the driver was unhurt.

The Yūbari Branch, which had outlived its coal-hauling purpose and carried only thin local traffic, became an early casualty of JR Hokkaido's retrenchment. In 2016 the loss-making 16.1-kilometre branch from Shin-Yūbari to Yūbari was identified for closure, and the company and the city of Yūbari reached agreement in March 2018, with JR Hokkaido contributing 750 million yen toward a replacement transport network. The last trains ran on 31 March 2019 and the branch was legally abolished the following day, leaving the Sekishō Line as the Minami-Chitose–Shintoku trunk route it is today.

• 18921 November: the Hokkaido Colliery and Railway Company opens the Yūbari Line, a Muroran-line branch from Oiwake through Momijiyama to Yūbari, to carry coal from the Yūbari coalfield.
• 19061 October: the Hokkaido Colliery and Railway Company is nationalised under the Railway Nationalization Act and the Oiwake–Yūbari line passes to the state railways.
• 190912 October: on the establishment of the official line-naming system, the route is designated the Yūbari Line.
• 1912Double-tracking of the line begins (Shimizusawa–Yūbari, 19 November 1912), continuing in stages through 1919.
• 1932November: following the 1930 opening of the parallel Yūbari Railway, traffic falls and the line is returned to single track.
• 197524 December: the last steam-hauled freight train runs on the Oiwake–Yūbari line, among the last scheduled steam freight workings in Japan.
• 19811 October: the new Chitose-Kūkō (now Minami-Chitose)–Oiwake and Shin-Yūbari–Kami-Ochiai Junction–Shintoku sections open; the Yūbari Line is absorbed and the whole route is renamed the Sekishō Line, with Momijiyama renamed Shin-Yūbari and the Shin-Yūbari–Yūbari stub becoming the Yūbari Branch.
• 198513 October: Yūbari Station is relocated about 1.3 km south.
• 19871 April: at the privatisation of Japanese National Railways, JR Hokkaido takes over the whole line and JR Freight becomes a second operator.
• 199026 December: Yūbari Station is relocated again, a further 800 m south.
• 19921 July: Chitose-Kūkō Station is renamed Minami-Chitose.
• 199722 March: a high-speed upgrade is completed, raising the line speed to 130 km/h and introducing the Super Ōzora limited express between Sapporo and Kushiro.
• 201127 May: a Super Ōzora service derails and catches fire inside the 685 m No. 1 Niniu Tunnel near Shimukappu; all aboard (about 240) escape and 39 are hospitalised, mainly for smoke inhalation; the line reopens on 30 May.
• 201216 February: a northbound JR Freight train held at a red signal at Higashi-Oiwake fails to stop, runs through the catch points and strikes a snow shelter; the locomotive and four wagons derail, with no injuries.
• 201430 August: the line's maximum operating speed is lowered to 120 km/h in connection with the deceleration of the Super Tokachi service.
• 201931 March: the last trains run on the Yūbari Branch (Shin-Yūbari–Yūbari, 16.1 km); it is legally abolished the next day, 1 April 2019.