Mini-shinkansen (ミニ新幹線) is the name given to the concept ofconverting1,067 mm (3 ft 6 in)narrow gauge railway lines to1,435 mm (4 ft 8+1⁄2 in)standard gauge for use byshinkansen train services in Japan. Unlike thehigh-speed Shinkansen lines, the mini-Shinkansen lines have a maximum speed of only 130 km/h (80 mph). Two mini-Shinkansen routes have been constructed: theYamagata Shinkansen andAkita Shinkansen.^[1]

The Mini-Shinkansen concept was first developed inJNR days, but was not formally proposed until November 1987, following the formation ofEast Japan Railway Company (JR East). The concept involved regauging existing3 ft 6 in (1,067 mm) gauge lines to standard gauge and linking them to the Shinkansen network to allow through-running. While the track gauge was widened, theloading gauge remained unchanged, requiring the construction of new Shinkansen trains with a narrower cross-section. These would be capable of running at high speed (theE6 series trains have a maximum speed capability of 320 km/h (199 mph)) on Shinkansen tracks, either on their own or coupled to full-sized sets, and run at conventional narrow-gauge speeds (around 130 km/h (81 mph)) on the mini-shinkansen tracks. Speeds on converted lines would also be raised where possible.^[1]

The first mini-Shinkansen route to be built was theYamagata Shinkansen, converted from the 87.1 km (54.1 mi) section of theŌu Main Line betweenFukushima on theTohoku Shinkansen andYamagata inYamagata Prefecture. Work started in 1988, with Yamagata Shinkansen services commencing on 1 July 1992. Services were operated by a new fleet of400 Series Shinkansen trains, at up to 240 km/h (150 mph) on the Tōhoku Shinkansen and 130 km/h (81 mph) on the Yamagata Shinkansen section.^[2] The success of this initiative led to the conversion of a further 61.5 km (38.2 mi) of the line toShinjō, opening on 4 December 1999.

Following the success of the Yamagata Shinkansen conversion, a scheme was proposed to construct a second mini-Shinkansen route fromMorioka inIwate Prefecture, then the northern terminus of theTohoku Shinkansen, withAkita inAkita Prefecture. This involved regauging the 75.6 km (47.0 mi)Tazawako Line from Morioka toŌmagari and 51.7 km (32.1 mi) of theŌu Main Line from Ōmagari to Akita.^[1] This opened on 22 March 1997 withKomachi services using newE3 Series Shinkansen trains.^[2]On 16 March 2013,E6 series trains entered service on this line, initially at a maximum speed of 300 km/h (186 mph) on the Tohoku Shinkansen section. In March 2014, the maximum speed on the Tohoku Shinkansen was increased to 320 km/h (199 mph).

The following rolling stock was built for use on mini-shinkansen lines.

• 400 Series Shinkansen, Yamagata Shinkansen (in service 1992–2010)
• E3 Series Shinkansen, Akita Shinkansen (in service 1997–2014) and Yamagata Shinkansen (from 1999)
• E926East i track and overhead wire inspection train (from 2001)
• E955Fastech 360Z experimental test train (2006-2008)
• E6 Series Shinkansen, introduced on the Akita Shinkansen in March 2013
• E8 Series Shinkansen, to be introduced on the Yamagata Shinkansen from 2024 onwards

• Gauge Change Train, an experimental train designed to operate on both narrow-gauge and standard-gauge routes
• Super Tokkyū, a concept of building narrow-gauge lines to Shinkansen standards

• Shinkansen
• Railway services introduced in 1992

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