Due to a policy being enforced in timetable revision made on November 1, 1986, where the number of cars in a set were reduced while the number of trains in operation during the daytime were increased, there were three-car train sets that existed from the end of the JNR period to the early JR period (six-car train sets, consisting of two three-car sets were run during rush hour).
1986年11月1日国鉄ダイヤ改正で編成両数を短くしつつ日中の運転本数を増やす施策が取られたため、国鉄末期からJR初期にかけては3両編成も存在した（ラッシュ時は2編成を併結した6両編成で運転）。