Sukumo Line

The route has its origins in a Japanese National Railways (JNR) project of the early 1960s. The Sukumo Line was made a survey line in March 1962 and was promoted to a construction line in June 1964; on 28 September 1964 the Minister of Transport directed the Japan Railway Construction Public Corporation to draw up a basic plan for the Sukumo–Nakamura section. The construction implementation plan was approved in October 1972, and work on the Sukumo–Nakamura line began in February 1974.

Before the line could be completed, national railway policy turned against new rural construction. Under the financial retrenchment that accompanied the JNR reform era, work on the line was frozen in October 1981. The project was rescued by the creation of a local third-sector operator: Tosa Kuroshio Railway was established on 8 May 1986 to take over railway schemes that JNR had begun but would not finish. The company received its operating authorisation in early 1987, and construction of the Sukumo Line resumed on 12 March 1987.

After more than two decades from its first designation, the line finally opened. On 1 October 1997 the 23.6-kilometre Sukumo–Nakamura section entered service as a Tosa Kuroshio Railway line, connecting at Nakamura with the company's existing Nakamura Line and extending rail service westward to the city of Sukumo. The line was built and opened as a modern non-electrified railway engineered for relatively high speeds, with a minimum curve radius of 350 metres.

Less than eight years after opening, the line was the scene of one of Japan's most severe over-run accidents. At about 20:41 on 2 March 2005, the down limited express "Nanpū 17", running from Okayama to Sukumo, entered the terminus at Sukumo Station at roughly 113 km/h instead of stopping. The three-car JR Shikoku 2000 series diesel multiple unit struck the buffer stop, smashed into the station building, destroyed an elevator and broke through an outer wall, the leading car being completely deformed and crushed by a telescoping effect.

The collision killed the driver and injured eleven other people, including the conductor and ten passengers; the designated cause was fatigued driving. Although the line was equipped with automatic train stop (ATS) protection, the positioning of the trackside equipment was not adequate for an approach at maximum speed. After the accident the operator installed additional time-element ATS-SS speed-checking trackside coils as an over-run-prevention measure, and JR Shikoku decided to add similar equipment at other dead-end terminal stations. Service was restored in stages: local trains resumed on 7 April 2005, limited expresses on 13 June 2005, and full passenger operation through to the station on 1 November 2005.

Today the Sukumo Line remains a rural single-track route at the western end of Tosa Kuroshio Railway's network. Numbered TK40 (Nakamura) through TK47 (Sukumo), it is worked by the company's own TKT-8000 series railcars together with JR Shikoku 2000 and 2700 series diesel units on through limited-express workings, providing the principal rail link to the Sukumo area of southwestern Kōchi.

• 196229 March: the Sukumo Line is designated a survey line.
• 196425 June: the Sukumo Line is promoted to a construction line; on 28 September the Minister of Transport directs the Japan Railway Construction Public Corporation to prepare a basic plan for the Sukumo–Nakamura section.
• 197224 October: the construction implementation plan for the line is approved.
• 1974February: construction of the Sukumo–Nakamura line begins.
• 1981October: work on the line is frozen amid the JNR reform-era retrenchment.
• 19868 May: Tosa Kuroshio Railway is established to take over railway projects JNR had begun but would not complete.
• 198712 March: with the operator authorised, construction of the Sukumo Line resumes.
• 19971 October: the 23.6 km Sukumo–Nakamura section opens as a Tosa Kuroshio Railway line, connecting at Nakamura with the Nakamura Line.
• 20052 March, ~20:41: the limited express "Nanpū 17" from Okayama enters Sukumo Station at about 113 km/h, strikes the buffer stop and crashes into the station building; the driver is killed and eleven others (the conductor and ten passengers) are injured. The designated cause is fatigued driving.
• 2005After the accident, time-element ATS-SS speed-checking trackside coils are installed as an over-run-prevention measure; service resumes in stages — local trains on 7 April, limited expresses on 13 June, and full passenger operation to Sukumo Station on 1 November.