Concerning the lines east of Ikoma Station, the construction of a line between Ikoma and Takanohara and of a line branching out somewhere between these two stations and extending toward Seika-cho and Nishi-Kizu Station were included in the 'Basic Plan for Kansai Scientific City' announced in 1982 by the National Land Agency (now the Ministry of Land, Infrastructure and Transport); moreover, in the tenth report by the Council for Transport Policy in 1989 it was described that a line should be constructed between Ikoma and Takanohara by 2005 and that the construction of a line branching out somewhere between these two stations and extending up to around Hosono Station (Shin-Hosono station in the eighth report by the Council for Kinki Regional Transport in 2004) had to be investigated together with the construction of a line up to the area between Takanohara and Kizu Station in Kyoto Prefecture.
生駒駅以東については、1982年に国土庁（現・国土交通省）が発表した「関西学術研究都市基本構想」で、生駒～高の原駅間と同区間から分岐して精華町・西木津駅方面へ向かう路線が示され、1989年の運輸政策審議会答申第10号では、生駒～高の原間が2005年までに整備すべき路線、同区間から分岐して祝園駅付近（2004年の近畿地方交通審議会答申第8号では新祝園駅）までと高の原～木津駅_(京都府)方面までが整備を検討すべき路線として盛り込まれた。