The is a Mini-shinkansen route in Japan, operated by East Japan Railway Company (JR East). It provides service between Tokyo and Shinjō in Yamagata Prefecture over the tracks of the Tohoku Shinkansen and the Ōu Main Line. The term Yamagata Shinkansen refers to the segment that connects Fukushima and Shinjō. Because the shinkansen trains share tracks with regular service trains, it is often referred to as a "mini-shinkansen". Operations Trains consist of 7-car E3 series trainsets operating as Tsubasa services. Between and Fukushima, the trains run coupled to Yamabiko trains on the Tōhoku Shinkansen. Between Fukushima and Shinjō, the trains run on their own at a maximum speed of and share the line with regular Ōu Main Line trains. As of July 2012, about 62 million passengers had ridden the line since it opened in July 1992. The fastest trains connected Tokyo and Yamagata stations in two hours and 29 minutes. Proposed Ou Base Tunnel Construction of a Base tunnel on the Yamagata Shinkansen is proposed, with JR East having undertaken a survey of a planned route from Niwasaka to Sekine, just south of Yonezawa station. of the proposed line would be in tunnel, mostly to the north of the existing Fukushima – Yamagata section. To be built on an improved alignment, the tunnel would lower journey times between Fukushima and Yamagata by ~10 min due to a proposed line speed of up to 200 km/h. The tunnel would avoid the Itaya Toge pass through the Ou mountains west of Fukushima. Gradients range from 3.0% to 3.8% and the line reaches an altitude of . The curvature and steep grades limit train speeds to or less, and the line is vulnerable to heavy rain and snowfall as well as high winds. Between 2011 and 2017 a total of 410 Yamagata mini-Shinkansen services were either suspended or delayed, and 40% of these incidents occurred on the line over the Itaya Toge pass. If the base tunnel is authorised, detailed design would take five years and construction another 15 years. The cost could increase by if the tunnel were to be built with a cross-section large enough to permit the line to be upgraded to the full Shinkansen loading gauge. Station list All stations listed below are located on the Ōu Main Line. Beyond Fukushima, trains bound for Tokyo run with Tohoku Shinkansen trains. Rolling stock As of March 2020, the following