The Yumo Line (now abolished) in Hokkaido was one of the candidates for this project, but the Yamaguchi Line was singled out because it was connected with the New Tokaido Line and had a lot of sightseeing spots.
これに関しては、北海道の湧網線（現・廃止）なども運転路線の候補に上げられたが、新幹線に接続し、観光地も多い山口線に白羽の矢が立った。