When the project of the Keihan Main Line to under-ground the section running in the Kyoto area started to take shape, finally Keihan Electric Railway and other entities established a company, Kamogawa Electric Railway (in 1972) and started the construction by the Japan National Railway Construction Public Corporation (JRCC) method (exactly the same method as the Kintetsu Higashi-Osaka Line (the current Kintetsu Keihanna Line, the section from Ikoma Station and to the west)).
京阪本線の京都地下線の建設が具体化するのにあわせ、1972年に京阪電鉄が中心となって鴨川電気鉄道が設立され、日本鉄道建設公団方式でようやく着工された（近鉄東大阪線（現・近鉄けいはんな線の生駒駅以西）と全く同じ手法である）。