Of the railway segments constructed as part of the Nakasen-do Main Line, the line connecting Ogaki and Kyoto via Kusatsu which made up the western part of the Nakasen-do route and the branch line connecting Obu and Ogaki were incorporated into the Tokai-do Line.
中山道幹線として建設された部分では、本線の西側部分になる大垣～草津～京都間と、支線の大府～大垣間が東海道線として組み込まれた。