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Iida Line

飯田線

The Iida Line is a 195.7-kilometre conventional railway line operated by the Central Japan Railway Company (JR Central) that connects Toyohashi Station in Toyohashi, Aichi Prefecture, with Tatsuno Station in Tatsuno, Nagano Prefecture, passing through northwestern Shizuoka Prefecture along the way.

It threads the steep gorge of the Tenryu River and the Ina Valley, linking eastern Aichi (the Higashi-Mikawa district) and southern Nagano through cities such as Iida and Ina. The line is mostly single-track (double-tracked only on the Toyohashi-Toyokawa section) and electrified at 1,500 V DC, built to the 1,067 mm narrow gauge, with a maximum operating speed of 85 km/h.

Unusually for a Japanese rural line, it has 94 stations (including both termini) over its 195.7 km, an average of only about 2.1 km between stops, as short as on an urban line in a big city. Because it was built to the modest standards of a local railway, the alignment is full of tight curves and steep grades; the 40-per-mille (4.0%) gradient between Akagi and Sawando became, after the closure of the Usui Pass section of the Shin'etsu Main Line between Yokokawa and Karuizawa, the steepest gradient on any JR line. The line has 138 tunnels, mostly in its mountain sections, and half of them (68) are concentrated in the 22.4 km between Hiraoka and Tenryukyo, where roughly 46% of the route runs underground.

Route of the Iida Line · Nagano · Shizuoka · Aichi · Borders: MLIT
A JR Central 313-3000 series local train crossing the Nakatagiri River with the Kiso Mountains behind, on the Iida Line.
A JR Central 313-3000 series local train crossing the Nakatagiri River with the Kiso Mountains behind, on the Iida Line. · MaedaAkihiko · CC BY-SA 4.0 · Wikimedia Commons

History

The Iida Line was not built as a single project but assembled from four independent private railways that were nationalised and merged during the Second World War. At the southern end, the Toyokawa Railway opened the first section, Toyohashi to Toyokawa, on 15 July 1897, reaching Omi by 1900; this section was fully electrified in 1925, and the following year the Aichi Electric Railway — a forerunner of the present-day Meitetsu — began running through onto it. The Horaiji Railway, an affiliate of the Toyokawa Railway, opened the Omi to Mikawa-Kawai section in 1923 and electrified it in 1925. At the northern end, the Ina Electric Railway (which began as the Ina Electric Tramway, partly running on street trackage) opened its first stretch from Tatsuno to Matsushima (now Ina-Matsushima) in 1909, progressively converting from tramway to railway and reaching Tenryukyo by 1927. The central gorge section, Mikawa-Kawai to Tenryukyo, was undertaken by the Sanshin Railway. Founded in 1927, when railways had become an object of speculation, the company was backed by electric-power interests that wanted the railway to carry materials for hydroelectric development on the Tenryu River. Construction through the fragile geology of the Median Tectonic Line and the sheer cliffs of the Tenryu gorge proved exceptionally difficult and costly, and the work became a grim chapter in Japanese railway history. The Sanshin Railway opened Tenryukyo to Kadoshima on 30 October 1932 as an electrified line, drawing its power from the Ina Electric Railway. It finally closed the last gap, between Ozore and Kowada, on 20 August 1937, completing a continuous electric railway from Toyohashi to Tatsuno some forty years after the Toyokawa Railway's first section had opened.

On 1 August 1943 the four companies — the Ina Electric Railway, the Sanshin Railway, the Horaiji Railway and the Toyokawa Railway — were bought out and nationalised, and the combined route was named the Iida Line. The Horaiji and Toyokawa companies, having lost their railways, were absorbed by the Nagoya Railroad (Meitetsu) the following year. Because the constituent lines had placed a station at almost every settlement along the way, the new national line inherited the very short station spacing that still characterises it. In 1955 two significant changes occurred: the catenary voltage of the Tenryukyo-Tatsuno section was raised from 1,200 V to 1,500 V DC on 15 April, unifying the line's electrification; and on 11 November the construction of the Sakuma Dam, which would have submerged the existing track, forced the abandonment of the 13.3 km Sakuma-Tenryu-Yamamuro-Ozore alignment in favour of a new 17.3 km line routed via Misakubo, which opened the stations of Aizuki, Shironishi, Mukaichiba and Misakubo. Centralised traffic control (CTC) was introduced in stages, on the Iida-Tatsuno section in February 1983 and on the Toyohashi-Iida section in February 1984. Until 1983 the line was famous among railway enthusiasts as a 'treasure house' of pre-war electric multiple units.

With the privatisation of Japanese National Railways on 1 April 1987, the Iida Line passed to JR Central; the Japan Freight Railway Company (JR Freight) became the second-category operator over the Toyohashi-Toyokawa and Motozenkoji-Tatsuno sections. The Inaji, which had run as an occasional express from 1992, became a regular limited express on 16 March 1996, and freight operation on the Motozenkoji-Tatsuno section ended on 30 September that year. In March 2018 JR Central gave the line a sky-blue line colour and introduced station numbering (line symbol 'CD') on the Toyohashi-Toyokawa section. JR Central is the first-category operator of the whole line, although JR East owns the railway assets at the northern terminus, Tatsuno. As of January 2026 the principal services are the limited express Inaji, which makes two round trips a day between Toyohashi and Iida, and the rapid Misuzu, which makes one round trip a day between Iida, Tatsuno and Nagano, running through onto the Chuo Main Line (Tatsuno Branch), the Chuo Main Line, the Shinonoi Line and the Shin'etsu Main Line; most local trains continue beyond Tatsuno to and from Okaya. Local trains run most often at the Toyohashi end, between Toyohashi and Toyokawa, and thin to one every one to three hours through the lightly populated mountain section between Hon-Nagashino and Tenryukyo. Current rolling stock includes JR Central 313-3000 and 373 series electric multiple units, plus JR East 211 series sets on inter-running services. JR Central's 213-5000 series ended regular service on 13 March 2026, and the long-serving 119 series, introduced in 1983, was withdrawn on 31 March 2012.

A JR East 211-3000 series train bound for Iida, with Komagatake in the background, on the Iida Line. View full size (opens in a new tab)
A JR East 211-3000 series train bound for Iida, with Komagatake in the background, on the Iida Line.MaedaAkihiko · CC BY-SA 4.0 · Wikimedia Commons

The line has an unusually large number of so-called 'hikyo-eki' or 'unexplored-region stations': isolated, little-used halts such as Kowada and Tamoto whose surrounding communities have largely vanished through depopulation. The term hikyo-eki was coined in 1999, and the Asahi Shimbun has described the line as the 'holy land for those who love touring hikyo-eki'. JR Central runs a dedicated tourist excursion, the 'Iida Line Hikyo-Eki' train, for visitors to these stations. For 187 km between Toyokawa and Tatsuno the line does not intersect any other railway, and as of 2025 it hosts the longest local train service in Japan: the 14:38 departure from Toyohashi reaches Okaya at 21:37, a 96-station journey of 6 hours 59 minutes (419 minutes). The line's steep, slide-prone course through the Tenryu gorge has also produced serious accidents, among them a National Railways replacement bus that plunged into the Tenryu River during a service suspension on 15 July 1951 with roughly 28 deaths, and a rockfall on 20 January 1955 between Tamoto and Kadoshima that derailed a two-car train into the Tenryu River (two killed and 27 injured). Farther north, a head-on collision of trains at Kitatono Station on 13 April 1989 injured well over a hundred people.

Stations on this line

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

Timeline
  • 189715 July: the Toyokawa Railway opens the first section, Toyohashi to Toyokawa; the line's oldest segment.
  • 1900The Toyokawa Railway reaches Omi, completing its line from Toyohashi.
  • 1909The Ina Electric Tramway (later Ina Electric Railway) opens its first section, Tatsuno to Matsushima (now Ina-Matsushima), at the northern end.
  • 1923The Horaiji Railway opens the Omi to Mikawa-Kawai section.
  • 1925The Toyokawa Railway is fully electrified, and the Horaiji Railway's section is electrified the same year.
  • 1926The Aichi Electric Railway (a Meitetsu forerunner) begins through-running onto the Toyokawa Railway.
  • 1927The Ina Electric Railway reaches Tenryukyo, completing its line. The Sanshin Railway is founded to build the central Tenryu gorge section.
  • 193230 October: the Sanshin Railway opens Tenryukyo to Kadoshima as an electrified line, drawing its power from the Ina Electric Railway.
  • 193720 August: the last gap (Ozore to Kowada) opens, completing a continuous electric railway from Toyohashi to Tatsuno about 40 years after the first section.
  • 19431 August: the four private railways (Ina Electric, Sanshin, Horaiji, Toyokawa) are nationalised and merged into the Iida Line. Horaiji and Toyokawa are absorbed by Meitetsu the following year.
  • 195515 April: the Tenryukyo-Tatsuno catenary is raised from 1,200 V to 1,500 V DC. 11 November: the Sakuma Dam forces rerouting of the Sakuma-Ozore section onto a new 17.3 km line via Misakubo.
  • 1983The 119 series EMUs enter service (14 February); CTC is introduced on the Iida-Tatsuno section. Until this year the line was a noted 'treasure house' of pre-war EMUs.
  • 1984February: CTC is introduced on the Toyohashi-Iida section.
  • 19871 April: JNR is privatised; the Iida Line passes to JR Central, with JR Freight as second-category operator on two sections.
  • 198913 April: a head-on collision of trains at Kitatono Station injures well over a hundred people.
  • 199616 March: the Inaji becomes a regular limited express. 30 September: freight operation on the Motozenkoji-Tatsuno section ends.
  • 201231 March: the 119 series EMUs are withdrawn after service from 1983.
  • 2014JR East 211 series EMUs are introduced on inter-running services north of Iida, replacing the 115 series.
  • 2018March: JR Central gives the line a sky-blue line colour and introduces station numbering (line symbol 'CD') on the Toyohashi-Toyokawa section.

Sources

Last updated 16 October 2026.

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