Gotemba Line

The line was built as part of the trunk railway linking Tokyo with Kobe. The Kōzu–Gotemba–Numazu(–Shizuoka) section opened on 1 February 1889, and the route took a deliberately indirect, mountainous path between Kōzu and Numazu to climb around the Hakone massif — the so-called "Kanrei-goe" pass. When a system of line names was established in 1896 this became part of the Tōkaidō Line, and in 1909, when the principal trunk routes were designated "main lines," it became part of the Tōkaidō Main Line.

Because it was a main line, the section was progressively double-tracked. Double-tracking began with the Oyama (now Suruga-Oyama)–Gotemba and Gotemba–Numazu stretches in 1891, and the entire Kōzu–Numazu line was double-tracked by 1901. Yet the steep "Kanrei-goe" gradients remained a serious operating obstacle for half a century: the weak steam locomotives of the day needed banking engines attached at Kōzu or Numazu and cut off at Gotemba, and even the prestigious "Tsubame" limited express, introduced in 1930, had to make brief banking stops on the climb.

The fundamental solution was to bypass the mountains entirely. Construction of the Atami Line from Kōzu toward Odawara and Atami had begun in 1918, and the difficult Tanna Tunnel was driven through the Tanna ridge to reach Numazu. When the tunnel opened on 1 December 1934 and the new flat coastal route via Atami was completed, the Tōkaidō Main Line was rerouted that way, and the old Kōzu–Gotemba–Numazu section was demoted to a branch and renamed the Gotemba Line. At the same moment the former Mishima Station on the line was renamed Shimo-Togari and a new Mishima Station opened on the new alignment; the diversion dealt a heavy economic blow to the towns along the old route.

The line's role shrank sharply during the Second World War. With traffic much reduced and steel urgently needed for the war effort, the Kōzu–Numazu line was designated a non-essential line and singled on 11 July 1943; the rails and bridge girders lifted from the redundant track were recovered, and from 1944 some of the material was reused for double-tracking the Yanai line absorbed into the San'yō Main Line and for bridges on the under-construction Yokosuka and Tarumi lines. Traces of the double-track era — embankments, tunnel bores and bridge piers built to twin-track width — are still visible from the train today.

In the post-war decades the branch was modernised and given a new connection to Tokyo. A connecting line between Shin-Matsuda and Matsuda opened in 1955, and through semi-express trains began running from Shinjuku to Gotemba over Odakyu Electric Railway's Odawara Line, worked by Odakyu's new twin-engined KiHa 5000 diesel railcars; local services were also dieselised and several new stations were added on former double-track land. Electrification was completed in two stages in 1968 — Kōzu–Gotemba on 27 April and Gotemba–Numazu on 1 July — and the Tokyo–Gotemba express "Gotemba" began running with electric trains. Regular freight handling was withdrawn along the Shimo-Soga–Numazu section on 15 November 1982.

At the division and privatisation of Japanese National Railways on 1 April 1987 the line passed to JR Central — uniquely, the only conventional line within Kanagawa Prefecture to do so rather than to JR East — while JR Freight became the line's Class II operator. Centralised traffic control was introduced across the whole line on 16 December 1989 and a programmed route control system from 10 March 1990. The Odakyu through service was upgraded to a limited express in 1991, mutually through-operated and extended to Numazu, before reverting in 2012 to Odakyu-only operation between Shinjuku and Gotemba; in 2018 it was renamed from "Asagiri" to "Mt. Fuji." Today the line carries hourly local trains between Kōzu and Numazu plus the "Mt. Fuji" express, and remains a standby bypass for the Tōkaidō Main Line when that route is blocked.

• 18891 February: the Kōzu–Gotemba–Numazu(–Shizuoka) section opens as part of the trunk railway between Tokyo and Kobe; Matsuda, Yamakita, Oyama (now Suruga-Oyama), Gotemba, Sano (now Susono) and Numazu stations open.
• 1891Double-tracking begins: Gotemba–Numazu on 12 January and Oyama–Gotemba on 1 March.
• 18961 April: under the new line-naming system the section becomes part of the Tōkaidō Line.
• 1901Double-tracking of the Kōzu–Numazu line is completed (Kōzu–Yamakita on 5 February, Yamakita–Oyama on 11 June).
• 190912 October: when the principal trunk routes are designated 'main lines,' the section becomes part of the Tōkaidō Main Line.
• 1930The 'Tsubame' limited express, introduced this year between Tokyo and Kobe, has to make brief banking-engine stops on the steep climb between Kōzu and Numazu.
• 19341 December: with the Tanna Tunnel open and the flat Atami route complete, the Tōkaidō Main Line is rerouted via Atami and the Kōzu–Gotemba–Numazu section (60.2 km) is demoted to a branch and renamed the Gotemba Line; the former Mishima Station becomes Shimo-Togari.
• 194311 July: designated a non-essential line, the Kōzu–Numazu line is singled; recovered rails and bridge girders are reused from 1944 on the Yanai line (then absorbed into the San'yō Main Line) and on the Yokosuka and Tarumi lines.
• 19551 September: diesel railcars are introduced on passenger trains. 1 October: the Shin-Matsuda–Matsuda connecting line opens and through Shinjuku–Gotemba semi-expresses begin over the Odakyu Odawara Line, worked by Odakyu's new twin-engined KiHa 5000 railcars.
• 196827 April: the Kōzu–Gotemba section is electrified and the Tokyo–Gotemba electric express 'Gotemba' begins. 1 July: the Gotemba–Numazu section is electrified, completing electrification of the whole line.
• 198215 November: regular freight handling on the Shimo-Soga–Numazu section is discontinued.
• 19871 April: at the division and privatisation of Japanese National Railways the line passes to JR Central — the only conventional line reaching into Kanagawa Prefecture to do so — and JR Freight becomes its Class II operator.
• 198916 December: centralised traffic control (CTC) is introduced across the whole line.
• 199116 March: the Odakyu through 'Asagiri' is upgraded to a limited express, mutually through-operated with JR Central and extended over the Shinjuku–Numazu route.
• 201217 March: the 'Asagiri' reverts to Odakyu-only operation between Shinjuku and Gotemba (60000 series 'MSE'); the through trains from JR East's Tokaido Line are also discontinued.
• 201817 March: the limited express 'Asagiri' is renamed 'Mt. Fuji' (Fujisan); line numbering 'CB' and a dark-green line colour are also introduced.