Ōu Main Line

The Ōu Main Line (奥羽本線, Ōu-honsen) is a railway line in Japan, operated by the East Japan Railway Company (JR East). It connects Fukushima Station through Akita Station to Aomori Station. Since the opening of the Yamagata Shinkansen on July 1, 1992, the Fukushima–Yamagata section (as well as the Yamagata–Shinjō section since 1999) is sometimes referred to as the Yamagata Line. The name of the line as a whole refers to the ancient provinces of Mutsu (陸奥) and Dewa (出羽), as it connects both ends of Mutsu by passing north–south through Dewa.

Ōu Main Line
Passing the moat of Yamagata Castle Site
left: Narrow gauge right:Standard gauge
Overview
Native name奥羽本線
TypeMain line
SystemJR East
StatusOperating
TerminiFukushima
Aomori
Stations102
Operation
Owner JR East
CharacterElevated, rural
Technical
Track length486.3 km (302.2 mi)
Number of tracks2
Track gauge1,067 mm (3 ft 6 in)
1,435 mm (4 ft 8 1⁄2 in)
Electrification20 kV AC, 50 Hz
Route map
Red indicates standard gauge tracks

Route data
  • East Japan Railway Company
  • Total distance: 486.3 km (302.2 mi) (Fukushima–Aomori, Tsuchizaki–Akitakō)
    • East Japan Railway Company
      • 484.5 km (301.1 mi) (Fukushima–Aomori)
    • Japan Freight Railway Company
      • 1.8 km (1.1 mi) (Tsuchizaki–Akitakō)
      • 256.2 km (159.2 mi) (Yokote–Aomori)
      • 4.8 km (3.0 mi) (Aomori–Aomori Stoplight Station)
  • Rail Gauge:
    • 1,067 mm (3 ft 6 in)
      • Shinjō–Ōmagari
      • Akita–Aomori
    • 1,435 mm (4 ft 8 1⁄2 in)
      • Fukushima–Yamagata
      • Uzen-Chitose–Shinjō
    • Both (1,067 mm (3 ft 6 in), 1,435 mm (4 ft 8 1⁄2 in))
      • Yamagata–Uzen-Chitose
      • Ōmagari–Akita
  • Stations: 102 (including freight stations)
  • Tracks:
    • Dual-track
      • Fukushima–Sekine (1968–91)
      • Akayu–Akayu Stoplight Station (1968)
      • Uzen-Nakayama–Uzen-Chitose (1968–86)
      • Ashisawa–Funagata (1975)
      • Nozoki–Innai (1968)
      • Ōmagari–Oiwake (1963–94)
      • Ugo-Iizuka–Hachirōgata (1969)
      • Kado–Moritake (1967)
      • Tsurugata–Maeyama (1969–71)
      • Takanosu–Hayaguchi (1969)
      • Ōdate–Nagamine (1968–71)
      • Ishikawa–Kawabe (1967–70)
    • Single-track
      • Sekine–Akayu
      • Akayu Stoplight Station–Uzen-Nakayama
      • Uzen-Chitose–Ashisawa
      • Funagata–Nozoki
      • Innai– Ōmagari
      • Oiwake–Ugo-Iizuka
      • Hachirōgata–Kado
      • Moritake–Tsurugata
      • Maeyama–Takanosu
      • Hayaguchi–Ōdate
      • Nagamine–Ishikawa
      • Kawabe–Aomori
  • Electrification: All (alternating current 20,000 V 50 Hz)
  • Block system: Automatic block system (except Tsuchizaki–Akitakō section (gearing block system))
  • Depots: Yamagata, Akita

Services

The Ōu Main Line is split into the following four sections. Due to the differences in the tracks of these sections, there are no trains that go through more than one (with the exception of an Akita–Shinjō connection). Local and rapid services on the line are generally operated by 701 series (entire line) and 719 series (Fukushima - Shinjō only) electric multiple unit trains.

Fukushima–Shinjō (148.6 km)

On this section, the Ōu Main Line shares the tracks with the Yamagata Shinkansen. The rail gauge is 1,435 mm (4 ft 8 1⁄2 in) to allow the Yamagata Shinkansen to run on it. The Ōu Main Line is known as the Yamagata Line on this section.

Shinjō–Ōmagari (98.4 km)

Crossing the Yamagata-Akita border, there is little demand in this section, and all trains except one limited-stop "Rapid" train run as all-stations "Local" trains.

Ōmagari–Akita (51.7 km)

On this section, the Ōu Main Line shares the tracks with the Akita Shinkansen. Because the Ōu Main Line occasionally runs from Akita to Shinjō as a local train, this section contains one standard gauge track and two narrow gauge tracks. Also, the few Komachi trains running on this section have the priority.

Akita–Aomori (185.8 km)

Together with the Kosei Line, Hokuriku Main Line, Shinetsu Main Line, Hakushin Line, and the Uetsu Main Line, the Ōu Main Line is one of the express lines and freight lines that make up the Nihonkai Jūkan-sen (Sea of Japan Trans-Japan Line).

Station list
Station Japanese Distance
(km)		 Rapid Transfers Location
Fukushima 福島 0.0
Fukushima Fukushima Prefecture
Sasakino 笹木野 3.8
Niwasaka 庭坂 6.9
Akaiwa 赤岩 14.6
Itaya 板谷 21.2 Yonezawa Yamagata Prefecture
Tōge 峠 24.5
Ōsawa 大沢 28.8
Sekine 関根 34.8
Yonezawa 米沢 40.1
Oitama 置賜 45.6
Takahata 高畠 49.9 Yamagata Shinkansen Takahata
Akayu 赤湯 56.1
Nanyō
Nakagawa 中川 64.4
Uzen-Nakayama 羽前中山 68.3 Kaminoyama
Kaminoyama Onsen かみのやま温泉 75.0 Yamagata Shinkansen
Mokichi Kinenkan-mae 茂吉記念館前 77.8
Zaō 蔵王 81.8 Yamagata
Yamagata 山形 87.1
Kita-Yamagata 北山形 89.0
Uzen-Chitose 羽前千歳 91.9 ■ Senzan Line
Minami-Dewa 南出羽 93.6
Urushiyama 漆山 94.9
Takatama 高擶 97.0 Tendō
Tendō-Minami 天童南 98.3
Tendō 天童 100.4 Yamagata Shinkansen
Midaregawa 乱川 103.4
Jimmachi 神町 106.3 Higashine
Sakuranbo Higashine さくらんぼ東根 108.1 Yamagata Shinkansen
Higashine 東根 110.6
Murayama 村山 113.5 Yamagata Shinkansen Murayama
Sodesaki 袖崎 121.5
Ōishida 大石田 126.9 Yamagata Shinkansen Ōishida
Kita-Ōishida 北大石田 130.8
Ashisawa 芦沢 133.7 Obanazawa
Funagata 舟形 140.3 Funagata
Shinjō 新庄 148.6
Shinjō
Izumita 泉田 154.2
Uzen-Toyosato 羽前豊里 161.3 Sakegawa
Mamurogawa 真室川 164.0 Mamurogawa
Kamabuchi 釜淵 173.2
Ōtaki 大滝 180.3
Nozoki 及位 185.8
Innai 院内 194.4 Yuzawa Akita Prefecture
Yokobori 横堀 198.4
Mitsuseki 三関 204.4
Kami-Yuzawa 上湯沢 207.1
Yuzawa 湯沢 210.4 ●
Shimo-Yuzawa 下湯沢 214.5 ↓
Jūmonji 十文字 217.8 ● Jumonji, Hiraka
Daigo 醍醐 221.2 ↓ Hiraka, Hiraka
Yanagita 柳田 224.4 ↓ Yokote
Yokote 横手 228.3 ● ■ Kitakami Line
Gosannen 後三年 234.7 ↓ Misato
Iizume 飯詰 239.8 ●
Ōmagari 大曲 247.0 ●
Daisen
Jingūji 神宮寺 253.0 ↓
Kariwano 刈和野 260.6 ●
Mineyoshikawa 峰吉川 265.4 ↓
Ugo-Sakai 羽後境 271.9 ↓
Ōbarino 大張野 280.0 ↓ Akita
Wada 和田 285.4 ●
Yotsugoya 四ツ小屋 292.3 ●
Akita 秋田 298.7 ●
Tsuchizaki 土崎 305.8 ｜
Kami-Iijima 上飯島 308.3 ●
Oiwake 追分 311.7 ● ■ Oga Line
Ōkubo 大久保 318.9 ● Katagami
Ugo-Īzuka 羽後飯塚 322.2 ●
Ikawa-Sakura 井川さくら 323.6 ● Ikawa
Hachirōgata 八郎潟 327.5 ● Hachirōgata
Koikawa 鯉川 333.0 ｜ Kotooka
Kado 鹿渡 338.4 ｜
Moritake 森岳 345.1 ● Yamamoto
Kita-Kanaoka 北金岡 349.4 ｜
Higashi-Noshiro 東能代 355.4 ● ■ Gonō Line Noshiro
Tsurugata 鶴形 360.3 ｜
Tomine 富根 365.5 ｜
Futatsui 二ツ井 372.2 ●
Maeyama 前山 379.5 ｜ Kita-Akita
Takanosu 鷹巣 384.9 ● Akita Nairiku Line
Nukazawa 糠沢 388.1 ｜
Hayaguchi 早口 393.5 ● Ōdate
Shimokawazoi 下川沿 397.7 ｜
Ōdate 大館 402.9 ● ■ Hanawa Line
Shirasawa 白沢 409.4 ｜
Jinba 陣場 416.5 ｜
Tsugaru-Yunosawa 津軽湯の沢 422.3 ｜ Hirakawa Aomori Prefecture
Ikarigaseki 碇ヶ関 427.2 ●
Nagamine 長峰 432.0 ｜ Ōwani
Ōwani-Onsen 大鰐温泉 435.3 ● Kōnan Railway Ōwani Line
Ishikawa 石川 440.7 ｜ Hirosaki
Hirosaki 弘前 447.1 ● Kōnan Railway Kōnan Line
Naijōshi 撫牛子 449.8 ｜
Kawabe 川部 453.4 ● ■ Gonō Line Inakadate
Kita-Tokiwa 北常盤 456.6 ● Fujisaki
Namioka 浪岡 462.1 ● Aomori
Daishaka 大釈迦 467.2 ｜
Tsurugasaka 鶴ヶ坂 473.4 ｜
Tsugaru-Shinjō 津軽新城 478.8 ●
Shin-Aomori 新青森 480.6 ●
Aomori 青森 484.5 ●

History

The Japanese national government built the Ou Main Line, starting construction from Aomori in 1894, from Fukushima in 1899 and linking the two sections in 1905. In 1909 the formal name of the line was declared.

Opening dates for the individual sections are as follows.

Ōu North Line
  • December 1, 1894: Aomori–Hirosaki
  • October 21, 1895: Hirosaki–Ikarigaseki
  • June 21, 1899: Ikarigaseki–Shirasawa
  • November 15, 1899: Shirasawa–Ōdate
  • October 7, 1900: Ōdate–Takanosu
  • November 1, 1901: Takanosu–Noshiro (present-day Higashi-Noshiro)
  • August 1, 1902: Noshiro–Gojōme (present-day Hachirōgata)
  • October 21, 1902: Gojōme–Akita
  • October 1, 1903: Akita–Wada
  • August 21, 1904: Wada–Jingūji
  • December 21, 1904: Jingūji–Ōmagari
  • June 15, 1905: Ōmagari–Yokote

Ōu South Line
  • May 15, 1899: Fukushima–Yonezawa
  • April 11, 1901: Yonezawa–Yamagata
  • August 23, 1901: Yamagata–Tateoka (present-day Murayama)
  • October 21, 1901: Tateoka–Ōishida
  • July 21, 1902: Ōishida–Funagata
  • June 11, 1903: Funagata–Shinjō
  • October 21, 1904: Shinjō–Innai
  • July 5, 1905: Innai–Yuzawa
  • September 14, 1905: Yuzawa–Yokote, completion of Fukushima–Aomori connection

Line upgrading

Various sections of the line have been double-tracked since 1963.

The section between Niwasaka and Akaiwa stations proved to be geologically unstable, with one of the original tunnels collapsing in 1910. A realignment involving two new tunnels was opened a year later. Geological instability was suspected as the cause of a derailment on the section in 1948 that killed three crewmen, and another realignment was undertaken when the section was double-tracked in 1968.

Itaya station was originally a reversing station, and was realigned as a through station in conjunction with the gauge conversion work (see below) in 1990.

Electrification

The Fukushima to Yonezawa section was electrified at 1,500 V DC in 1949, and the Uzen-Chitose - Yamagata section in conjunction with the Senzan Line (also at 1,500 V DC) in 1960. Trials on the Senzan Line subsequently resulted in the adoption of 20 kV AC for all further electrification, and the abovementioned sections were converted to the new standard when the Yonezawa to Yamagata section was electrified in 1968. The Aomori to Akita section was electrified (at 20 kV AC) in 1971, as was the Akita to Uzen-Chitose section in 1975.

Former connecting lines
Akayu human powered tramway
Kosaka Railway sulphuric acid train in its final year of operation
Kawabe station with a Konan Railway train bound for Kuroishi in 1997
  • Akayu Station: The Yamagata Prefectural Government operated a 2 km 610 mm (2') gauge human powered tramway between 1919 and 1926.
  • Oishida Station: The Obabazawa Railway opened a 3 km line to its namesake town in 1916, the line closed in 1970.
  • Yuzawa Station: The Ogachi Railway Co. opened a 12 km line to Zentsu, electrified at 600 V DC, between 1928 and 1935. The last 3 km section closed in 1967, the electrification was decommissioned in 1971 and the rest of the line closed in 1973.
  • Yokote Station: The Yokote Railway opened a 38 km line to Oikata between 1918 and 1930. Construction commenced on an extension to Maego station on the company's Yuri Kogen Railway Chokai Sanroku Line but was not completed. The 12 km section from Oikata to Niiyama was closed following typhoon damage in 1947, the 7 km section from Niiyama to Tateai closed in 1965 when a bridge was destroyed by floodwaters, and the balance of the line closed in 1971.
  • Akita Station: The 762 mm (2'6") gauge Nibetsu Forest Railway, consisting of a 22 km main line and five branches between 1.3 km and 5 km in length (and a 550 m tunnel) operated between 1909 and 1968.
  • Hachirogata Station: The Akita Chuo Kotsu operated a 4 km line to Gojome, electrified at 600 V DC, from 1922 until 1969.
  • Odate Station: The Kosaka Railway opened a 23 km 762 mm gauge line to its Kosaka Refinery in 1908, together with a 4 km branch from Shigenai to Kizawa the following year. Passenger services ceased on the Kizawa branch in 1926, and it closed in 1951. The 10 km Kosaka to Shigenai section was electrified in 1928, and extended 6 km in 1949, but was decommissioned when the line was converted to 1,067 mm gauge in 1962. Passenger services ended in 1994, and the remaining traffic was sulphuric acid, but following two major derailments the line closed in 2009.

The company also opened a 5 km 762 mm gauge line to the Hanaoka mine in 1914 including a bridge over the Ou Main Line at Odate, which was converted to 1,067 mm gauge in 1951 to enable ore wagons to be forwarded via JNR trains. Freight services ceased in 1983 and the line closed in 1985.

  • Kawabe Station: The 7 km line to Kuroishi was opened in 1912, transferred to the Konan Railway in 1984, the year that freight services ceased, and closed in 1998.

Gauge conversion

Full standard Shinkansen lines are constructed using 1,435 mm gauge track on a separate alignment, with a high speed (240–320 km/h or 150–200 mph) and a commensurately high construction cost. Following privatisation and regionalisation of the JNR network in 1987, the JR East company decided to convert the Fukushima–Yamagata section of the 1,067 mm gauge Ou Main line to 1,435 mm gauge, enabling Shinkansen trains from Yamagata to travel on the Tohoku Shinkansen line through to Tokyo. Called Mini-shinkansen, this was a cost-effective way of providing an improved level of service on the line, although only purpose-built Shinkansen trains can travel on such lines, as the loading gauge was not changed, nor the voltage (full standard Shinkansen lines use 25 kV AC). The Yamagata Shinkansen opened in 1992, and although the maximum speed is 130 km/h (81 mph), the overall transit time to places beyond Fukushima is improved due to the elimination of the need to change trains at the junction.

The success of this project led to the conversion of the Omagari to Akita section in conjunction with the opening of the Akita Shinkansen in 1997, and the extension of the Yamagata Shinkansen to Shinjo in 1999. These projects also created parallel 1,435 and 1,067 mm gauge lines between Omagari and Akita and between Yamagata and Uzen-Chitose respectively, and a dual-gauge section between Jinguji and Minejoshikawa (on the Omagari to Akita section), enabling Shinkansen trains to pass at speed on the mostly single-track line.

Additionally, local services continue to be provided on the gauge-converted lines by 701-5000 series standard-gauge suburban/interurban rolling stock.

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References
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