Which Shinkansen route opened in 1992 as Japan's first mini-shinkansen?

The Yamagata Shinkansen opened in 1992 as Japan’s first mini-Shinkansen route.

It began service on July 1, 1992, linking Fukushima with Yamagata over a regauged section of the Ōu Main Line. The conversion allowed specially built Shinkansen trains to run directly from Tokyo via the Tōhoku Shinkansen without requiring passengers to change trains.

“Mini” refers to the infrastructure, not a toy or low-capacity train. Existing conventional tracks were widened to standard gauge, but their narrower loading gauge remained, requiring slimmer trainsets. The route’s conventional-line section has a maximum speed of about 130 km/h, far below full-size Shinkansen lines.

The Akita Shinkansen, opened in 1997, was the second mini-Shinkansen. A common mix-up is confusing the route with the Tsubasa service: Tsubasa is the named train service operating on the Yamagata Shinkansen.