The local trains were divided into two routes: departure/arrival at Suita Station and at Koshienguchi Station, because if all the trains were to run straight between Nishi-Akashi Station and Kyoto Station they would be unable to escape from the special rapid running on the inner line, which was at that time a shared lane.
吹田・甲子園口発着に系統分割されたのは、普通を西明石→京都間通し運転すると当時内側線を共用していた新快速から逃げ切れなくなるためである。