Hakubi Line

The corridor grew out of a contested scheme to bridge the Chūgoku Mountains. A licence was first granted to the private Chūgoku Railway, but financial difficulties in the recession that followed the Russo-Japanese War left the plan stalled. The Railway Agency then decided to build the Hōki-Daisen–Neu section as a light railway at state expense under the name Negi Line. While that work was under way, plans for a full main-line connection took shape; after lobbying by the Kurashiki industrialist Ōhara Magosaburō the junction with the San'yō Main Line was fixed at Kurashiki, and in 1918 the project was renamed the Hakubi Line and laid out as a full railway on its present alignment.

Construction proceeded from both ends. The northern part opened first, as the Hakubi North Line (伯備北線), between Hōki-Mizoguchi and Hōki-Daisen on 10 August 1919, and was then extended south stage by stage — to Ebi (1922), Neu (1922), Kurosaka (1922), Shōyama (1923), Kami-Iwami (1924) and Ashidachi (1926). The southern part opened as the Hakubi South Line (伯備南線) on 17 February 1925 between Kurashiki and Shisawa (now Gōkei), and pushed north through Minagi (1925), Bitchū-Takahashi (1926) and on to Bitchū-Kawamo by 31 July 1927.

The two halves were joined on 25 October 1928, when the Bitchū-Kawamo–Ashidachi section opened; from that date the South Line absorbed the new segment and the North Line, the whole route was renamed the Hakubi Line, and stations including Hōkoku, Ikura, Ishiga, Niimi and Bitchū-Kōjiro opened. The line had been built to modest "Class C" local-railway standards and was at first regarded as a minor cross-mountain route, less important than the parallel Kisuki and Geibi lines.

The line's fortunes were transformed by the Shinkansen. Once the early opening of the Shin-Ōsaka–Okayama section of the San'yō Shinkansen was decided, the Hakubi Line was developed as the short cut linking Okayama with Yonago, Matsue and Izumoshi. The limited express "Yakumo" — running from Okayama to Izumoshi via the line — began on 15 March 1972, in step with the Shinkansen reaching Okayama. Through the early 1970s the route was progressively upgraded with realignments and double-tracking: the Kiyone–Bitchū-Takahashi section was doubled between 1968 and 1973, Kurashiki–Kiyone in 1979, and the Ikura–Ishiga section between 1982 and 1983 in conjunction with a realignment that shortened the route. CTC signalling was introduced across the line in the early 1970s. Until the end of steam in 1972–73, the climb over the Chūgoku Mountains was famous for triple-headed D51 locomotives hauling limestone trains, and Nunohara signal box drew railway photographers from all over Japan.

Electrification at 1,500 V DC was completed over the whole Kurashiki–Hōki-Daisen route on 1 July 1982, together with the San'in Main Line as far as Chiimiya (now Nishi-Izumo) — making the Hakubi Line the first of the in'yō connecting routes to be electrified. The "Yakumo" was switched to electric traction, worked by tilting 381 series electric multiple units. Under the breakup and privatisation of Japanese National Railways on 1 April 1987 the line passed to JR West, with Japan Freight Railway (JR Freight) operating over it as a Type-2 operator and the Nunohara signal box becoming Nunohara Station.

Improvements continued under JR West: 120 km/h running for the "Yakumo" south of Bitchū-Takahashi began in 1990, and from 1 July 1998 the line was chosen as the route for the new "Sunrise Izumo" sleeper service, giving the Hakubi Line its first regular overnight train and its first regular through service from Tokyo. The route has seen serious natural disruptions — services were cut for several days by the 2000 Western Tottori earthquake, and again by the July 2018 West Japan heavy-rain disaster, after which the whole line reopened on 1 August 2018. After years of reduced timetables, the "Yakumo" was restored to fifteen round trips a day in the March 2024 revision, and from 6 April 2024 the long-serving 381 series began to be replaced by new 273 series trains. Today the Hakubi Line remains the busiest and best-equipped of the cross-Chūgoku routes, carrying the "Yakumo", the "Sunrise Izumo" and freight alongside local services, though single-track sections and sharp curves through the mountains still remain.

• 191910 August: the Hakubi North Line opens between Hōki-Mizoguchi and Hōki-Daisen (about 11.3 km), the first section of the future line.
• 1922The Hakubi North Line is extended south to Ebi (25 March), Neu (30 July) and Kurosaka (10 November).
• 19246 December: the Hakubi North Line reaches Kami-Iwami (after extending to Shōyama in 1923).
• 192517 February: the Hakubi South Line opens between Kurashiki and Shisawa (now Gōkei), then is extended to Minagi on 17 May.
• 1926The South Line is extended to Kinoyama via Bitchū-Takahashi (20 June) and the North Line reaches Ashidachi (1 December).
• 192731 July: the Hakubi South Line is extended from Kinoyama to Bitchū-Kawamo.
• 192825 October: the Bitchū-Kawamo–Ashidachi section opens, joining the north and south sections; the whole route is renamed the Hakubi Line and Niimi and other stations open.
• 1968Double-tracking of the Kiyone–Bitchū-Takahashi corridor begins (Kiyone–Sōja–Gōkei doubled in September), continuing through 1973.
• 197215 March: the limited express "Yakumo" begins running, in step with the San'yō Shinkansen reaching Okayama; CTC is introduced on the Kurashiki–Niizato section and the last triple-headed D51 steam run is made.
• 19799 October: the Kurashiki–Kiyone section is double-tracked (the Niimi–Nunohara side having been partly doubled in March).
• 19821 July: the whole Kurashiki–Hōki-Daisen route is electrified at 1,500 V DC — the first in'yō connecting line to be electrified — and the "Yakumo" switches to 381 series electric trains.
• 19871 April: with the breakup and privatisation of Japanese National Railways, the line passes to JR West; JR Freight becomes a Type-2 operator and the Nunohara signal box becomes Nunohara Station.
• 199010 March: 120 km/h running for the "Yakumo" begins south of Bitchū-Takahashi.
• 19981 July: the new "Sunrise Izumo" sleeper is routed via the Hakubi Line, the line's first regular overnight train and first regular through service from Tokyo.
• 2018From 5 July the July 2018 West Japan heavy-rain disaster suspends services across the line; the whole line reopens on 1 August (Nunohara Station on 27 August).
• 2024The March timetable revision restores the "Yakumo" to fifteen round trips a day, and from 6 April the new 273 series begins replacing the long-serving 381 series.