In fact, type 103 cars were already running at that time on the Joban Line (currently the Joban Rapid Line) and the Hanwa Line Rapid where distances between stations are long and high-speed performance is required.
実際、103系もこの頃には常磐線（現在の常磐快速線）や阪和線快速といった駅間距離も長く高速性能を要求される線区にも投入されていた。