Even the old-type limited express manufactured in the era of JNR can run at a speed of 140 km/h (ordinarily, the highest speed is limited to 120 km/h) inside the Seikan tunnel, and the ATC-L type automatic train control device, compatible with the analog ATC used in Shinkansen, is employed (however, each JR company is digitizing the ATC system, and it is highly likely that the ATC-L will be replaced with a digital ATC after the construction of the Hokkaido Shinkansen line is completed).
青函トンネル内は国鉄時代に製造された旧型特急車両（通常制限最高速度120km/h）でも140km/h現示まで出せ、新幹線のアナログATCと互換性のある自動列車制御装置ATC-L形を採用している（ただしJR各社はATCシステムのデジタル化を進めており、北海道新幹線建設後は置き換えられる可能性が高い）。