Honshi–Bisan Line

The line's defining feature is the Great Seto Bridge, a chain of bridges spanning the islands of the Seto Inland Sea. The railway is carried on the lower deck of a combined rail–road structure, running beneath the Seto-Chūō Expressway that occupies the upper deck. Only six stations lie on the route — Chayamachi, Uematsu, Kimi, Kaminochō and Kojima in Okayama Prefecture, then Utazu on the Shikoku side — with the long bridge crossing falling between Kojima and Utazu. The company boundary sits at Kojima, 12.9 km from Chayamachi: the 12.9 km to Kojima are operated by JR West and the 18.1 km on to Utazu by JR Shikoku.

The project to build a rail connection across the Seto Inland Sea became entangled in the financial crisis of the Japanese National Railways (JNR) in the early 1980s. As the government moved to rein in JNR's mounting debts, the railway portion of the Seto Bridge came under scrutiny. On 21 July 1983 it was reported that the JNR Reconstruction Supervisory Committee had resolved to recommend to the prime minister that construction of the Kojima–Sakaide railway works be halted, on the grounds that JNR could not afford the usage fees for the bridge's railway portion, which would have exceeded its annual passenger revenue in Shikoku at the time. Political pressure from Shikoku interests kept the suspension out of the committee's subsequent emergency recommendations, and the project went ahead.

The line opened in two stages in 1988. On 20 March the 13 km section between Chayamachi and Kojima opened on a provisional basis, timed to carry visitors to the Seto Great Bridge Expo '88 ('Seto-Ōhashi Haku '88'). Then on 10 April the 18 km Kojima–Utazu section opened together with a connecting cut-off line to Sakaide, coinciding with the inauguration of the Great Seto Bridge road-and-rail system. This completed the through route and provided the first rail connection between Honshu and Shikoku; until then passengers had travelled via the Uno Line and a train ferry to Takamatsu. The opening also facilitated electrification of the Yosan Line between Takamatsu and Matsuyama on Shikoku.

From 22 July 1989 the maximum speed of limited-express diesel railcars on the bridge was cut from 95 km/h to 65 km/h. The restriction was eased on 21 November 1991, when only the 2000 series diesel railcars were permitted to return to 95 km/h on the bridge. A surcharge fare was applied to the Kojima–Utazu section from 10 January 1996, an extra charge that has remained a feature of fares over the bridge.

The enormous cost of the crossing left a long financial tail. The debt of the Seto-Ōhashi rail division, amounting to some 490 billion yen, was repaid in full. ICOCA smart-card coverage reached the Chayamachi–Kojima section on 1 September 2007 and the Kojima–Utazu section, with the Sakaide cut-off, on 1 March 2014. JR West also gave its part of the line a route identity, assigning the colour blue and the route symbol “M.”

The Honshi-Bisan Line carries the Marine Liner rapid service between Okayama and Takamatsu as well as limited expresses to Matsuyama and Kōchi, alongside JR Freight traffic. One-man operation was introduced on local trains over the Chayamachi–Kojima section from 15 March 2025.

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

• Chayamachi茶屋町
• Kaminocho上の町
• Kimi木見
• Kojima児島
• Uematsu植松
• Utazu宇多津

• 198321 July: it is reported that the JNR Reconstruction Supervisory Committee has resolved to recommend halting construction of the Kojima–Sakaide railway works, as JNR cannot afford the usage fees for the bridge's railway portion, which would exceed its annual passenger revenue in Shikoku at the time; Shikoku political pressure keeps the suspension out of the committee's emergency recommendations.
• 198820 March: the 13 km Chayamachi–Kojima section opens on a provisional basis, timed to carry visitors to the Seto Great Bridge Expo '88.
• 198810 April: the 18 km Kojima–Utazu section and a connecting cut-off line to Sakaide open with the inauguration of the Great Seto Bridge system, completing the first rail link between Honshu and Shikoku (previously served by the Uno Line and a train ferry) and facilitating electrification of the Yosan Line between Takamatsu and Matsuyama.
• 198922 July: the maximum speed of limited-express diesel railcars on the Seto bridge is reduced from 95 km/h to 65 km/h.
• 199121 November: only the 2000 series diesel railcars are allowed to return to 95 km/h on the bridge.
• 199610 January: a surcharge fare is introduced on the Kojima–Utazu section.
• 1999/2001The debt of the Seto-Ōhashi rail division, some 490 billion yen, is fully repaid. The year is given as 1999 or 2001.
• 20071 September: the Chayamachi–Kojima section is added to the ICOCA smart-card area.
• 20141 March: the Kojima–Utazu section and the Sakaide cut-off line are added to the ICOCA smart-card area.
• 202515 March: one-man operation begins on local trains over the Chayamachi–Kojima section.