| The Nagasaki route of the Kyushu Shinkansen line: between Shin-Tosu Station and Takeo-Onsen Station, and between Isahaya Station and Nagasaki Station (located in Nagasaki Prefecture) (for the section between Hizen-Yamaguchi Station and Takeo-Onsen Station, there are investigations to make the existing regular line a two-track line) |
九州新幹線長崎ルート 新鳥栖駅 - 武雄温泉駅、諫早駅 - 長崎駅 (長崎県)間（肥前山口駅 - 武雄温泉駅間については在来線複線化を検討中） |