Since enhancing transport capacity of the Yokosuka Line was urgently needed in particular, type 70 cars of the Keihanshin Local Line were transferred to the Yokosuka Line because the development of new suburban car operating on DC was delayed.
中でも、横須賀線の輸送力増強は焦眉の急であったが、直流用の新性能近郊型電車の導入までにはまだ時間がかかることから、京阪神緩行線の70系を転属させて投入することにした。