Mini-Shinkansen
Mini-Shinkansen is the name given to the concept of converting existing [3 ft 6 in gauge railways|] narrow gauge railway lines to to allow operation of Shinkansen services in Japan. While the track gauge is widened, the original loading gauge is retained, requiring the use of specially designed Shinkansen rolling stock with a narrower cross-section, leading to the "mini-Shinkansen" designation.
Unlike purpose-built high-speed Shinkansen lines, mini-Shinkansen routes are constrained by their legacy infrastructure to maximum operating speed of. Two mini-Shinkansen routes have been constructed: the Yamagata Shinkansen, which opened in 1992, and the Akita Shinkansen, which opened in 1997. Both connect to the high-speed Tōhoku Shinkansen for direct service to and from Tokyo.
Concept
The mini-Shinkansen concept was first considered by Japanese National Railways, but was not formally proposed until November 1987, following the formation of East Japan Railway Company. The concept involves regauging existing narrow gauge lines to the used on the Shinkansen network, to allow through-running on a main high-speed Shinkansen line. While the track gauge is widened, the loading gauge remains unchanged, requiring specialized rolling stock with a narrower cross-section, compared to the standard width.To compensate for the narrower car bodies, these trains generally have 2×2 seating in ordinary class, compared with the 2×3 configuration of typical Shinkansen trains, and are fitted with retractable gap fillers that flip up at main line Shinkansen stations to bridge the gap between the train and the platform.
Mini-Shinkansen sets are capable of high-speed operation on Shinkansen tracks—up to for the E6 series—either on their own or coupled to full-sized Shinkansen sets. On converted narrow-gauge lines, they operate at conventional speeds of around, although track improvements can enable higher speeds where feasible.