Originally the shortest route between Tsuruga and Kyoto was by way of the Kosei Line, but the direct line going through Tsuruga was not set up and instead the direct line going through the Maizuru Line and the Sanin Main Line was set up, because it met the coming and going from Kyoto, Osaka region to the west of Wakasa region and it also undertook the local transportation on the Obama Line (for example, we can raise the local trains directly linking Tsuruga with Fukuchiyama or the express train 'Tango' and so on, whose departure and arrival was in Kyoto and which ran as a local train eastward from Higashi-Maizuru, that is, on the Obama Line).
そもそも、敦賀-京都間は湖西線経由が最短ルートなのに、敦賀経由の直通列車は設定されず、舞鶴線・山陰本線経由で直通列車を設定していたのは、京都・大阪方面から若狭地方西部への出入りに対応したのと、小浜線内の地域輸送とを兼用したためである（例として敦賀-福知山間を直通していた普通列車や、東舞鶴以東つまり小浜線内が普通列車となる京都発着の急行「丹後」などが挙げられる）。