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Senzan Line

仙山線

The Senzan Line (仙山線, Senzan-sen) is a 58.0-kilometre railway line operated by the East Japan Railway Company (JR East) that crosses the Ōu Mountains of southern Tōhoku, linking Sendai Station in Miyagi Prefecture with Yamagata Station in Yamagata Prefecture by way of the temple town of Yamadera. It is laid to 1,067 mm narrow gauge and is electrified throughout at 20 kV 50 Hz AC.

Officially the line runs from Sendai to Uzen-Chitose, where it joins the Ōu Main Line for the final approach into Yamagata, and it links the Tōhoku Main Line and Tōhoku Shinkansen at Sendai with the Ōu Main Line and the Yamagata Shinkansen at the Yamagata end. Its name is formed from the first characters of the two cities it joins: Sendai (仙台) and Yamagata (山形). The line is historically significant as the proving ground for Japan's first AC railway electrification.

SendaiYamagata10 km
Route of the Senzan Line · Miyagi · Yamagata · Boundaries: MLIT / GSI / Japan Post

History

Proposals to connect Sendai and Yamagata by rail date back to the mid-1880s, but the choice of route across the mountains — over the Sekiyama, Futakuchi or Sasaya passes — divided the municipalities concerned, each of which lobbied for its own route. The cities unified their lobbying efforts in 1919, and the line was written into the (revised) Railway Construction Act in 1922; the Imperial Diet session that opened that December approved it, with construction to begin in 1923. The Great Kantō Earthquake of 1923 delayed the start, and work on the Miyagi side did not begin until around 1926.

The railway was opened in stages from each end toward the mountains in the middle. On 29 September 1929 the Senzan East Line began operation between Sendai and Ayashi (15.2 km), opening Kita-Sendai, Rikuzen-Ochiai and Ayashi stations; this section was extended to Sakunami (13.5 km) on 30 August 1931. From the Yamagata end, the Senzan West Line opened between Uzen-Chitose and Yamadera (9.3 km) on 17 October 1933. Both end sections were initially worked by steam locomotives.

The two halves were joined on 10 November 1937, when the difficult mountain section between Sakunami and Yamadera (20.0 km) opened and the through route was renamed the Senzan Line. The heart of this section was the 5,361-metre Senzan Tunnel, at the time the third-longest railway tunnel in Japan after the Shimizu Tunnel on the Jōetsu Line and the Tanna Tunnel on the Tōkaidō Main Line. Because steam haulage was unsuitable for the long bore, the Sakunami–Yamadera segment was electrified from the outset at 1,500 V DC and worked by electric locomotives, while the outer sections continued under steam.

From October 1954 Japanese National Railways used the line as a test bed for commercial-frequency AC traction, beginning with trials between Rikuzen-Ochiai and Rikuzen-Shirasawa; in April 1955 the test section was widened to run from Kita-Sendai to Sakunami, and the experiments — Japan's first AC railway electrification — continued until April 1956. The data and technology gained in these trials were later applied to the AC electrification of Japan's trunk lines and to the trains that ran on them. In 1957 the AC system was extended into Sendai Station, with AC-hauled freight running from July of that year, and purpose-built locomotives such as the ED45 (later ED91) were put into service.

Electrification of the rest of the line followed. The Yamadera–Uzen-Chitose section (continuing to Yamagata) was wired at 1,500 V DC on 1 November 1960, and around the same time the line gained named semi-express services such as the Asahi, Gassan and, from 1963, the Senzan. On 8 September 1968 the Sakunami–Uzen-Chitose section was converted to 20 kV 50 Hz AC, and immediately before that year's "Yonsantō" timetable revision the whole Senzan Line was unified under AC electrification.

Under the 1987 break-up and privatisation of Japanese National Railways, the Senzan Line passed on 1 April 1987 to JR East as the operating (Class 1) company, with JR Freight holding Class 2 freight rights. During construction of the Yamagata Shinkansen in the early 1990s, the Tsubasa limited express and the Tsugaru express were diverted over the line. When the Yamagata Shinkansen was extended to Shinjō in December 1999, the double-track Ōu Main Line between Uzen-Chitose and Yamagata became one standard-gauge track and one narrow-gauge track, the latter kept for Senzan Line and Aterazawa Line trains. Freight service ended in 2002. All regular trains are now E721-series electric multiple units, which replaced the earlier 719 and 701 series. The Sendai–Ayashi section, in Sendai's suburbs, carries heavy commuter traffic, while beyond Ayashi the timetable is built around the inter-city link between Sendai and Yamagata.

Stations on this line

18 stations tracked on the map, listed alphabetically. Select any to read its page.

Timeline
  • 1922The Senzan Line is stipulated in the (revised) Railway Construction Act.
  • 192929 September: the Senzan East Line opens between Sendai and Ayashi (15.2 km); Kita-Sendai, Rikuzen-Ochiai and Ayashi stations open.
  • 193130 August: the East Line is extended from Ayashi to Sakunami (13.5 km); Rikuzen-Shirasawa, Kumagane and Sakunami stations open.
  • 193317 October: the Senzan West Line opens between Uzen-Chitose and Yamadera (9.3 km); Tateyama and Yamadera stations open.
  • 193710 November: the Sakunami–Yamadera mountain section (20.0 km) opens, connecting Sendai and Uzen-Chitose; the through route is renamed the Senzan Line and the Sakunami–Yamadera section is electrified at 1,500 V DC. It includes the 5,361 m Senzan Tunnel, then Japan's third-longest after the Shimizu and Tanna tunnels.
  • 1954October: Japanese National Railways begins AC electrification testing on the line, starting between Rikuzen-Ochiai and Rikuzen-Shirasawa — the first such trials in Japan.
  • 195510 August: the Rikuzen-Ochiai–Kumagane section is electrified at 20 kV 50 Hz AC as part of the AC test line; in April the test section had been widened to run Kita-Sendai–Sakunami.
  • 1957AC electrification is extended to Sendai Station; AC-hauled freight begins in July, and the ED45 (later ED91) electric locomotive enters service.
  • 19601 November: the Yamadera–Uzen-Chitose (–Yamagata) section is electrified at 1,500 V DC; the Asahi and Gassan semi-expresses begin.
  • 19631 October: the Senzan semi-express begins operation between Sendai and Yamagata.
  • 19688 September: the Sakunami–Uzen-Chitose (–Yamagata) section is converted to 20 kV 50 Hz AC, and the whole line is unified under AC electrification just before the 'Yonsantō' timetable revision; the ED78 locomotive enters service.
  • 198215 November: the Senzan express is downgraded to a rapid train and the Gassan express ceases operation on the Senzan Line.
  • 19871 April: with the break-up and privatisation of Japanese National Railways, the line passes to JR East (Class 1) and JR Freight (Class 2).
  • 199127 August: the Tsubasa limited express is diverted over the Senzan Line during construction of the Yamagata Shinkansen.
  • 1999December: with the extension of the Yamagata Shinkansen to Shinjō, the double-track Ōu Main Line between Uzen-Chitose and Yamagata becomes one standard-gauge track and one narrow-gauge track, the latter kept for Senzan Line and Aterazawa Line trains.
  • 20021 April: freight services cease on the Senzan Line.

Sources

Last updated 16 October 2026.

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