Series 12 Passenger Cars are Express Coach Passenger Cars which were manufactured in the period from 1968 to 1978 to comply with the maximum operational speed of 110 km/h.
They were equipped with apparatus, which were as good as those for then electric or diesel trains, such as air conditioning device working with the power from diesel generator under the floor. Thus they made the base for succeeding new type passenger cars, series 14 and later cars. Series 12 Passenger Cars were operated first as special trains or trains for Osaka World Expo and then as regular express trains across Japan except Hokkaido. In the later years, some of them were modified into commuter trains and some of them converted into excursion trains dubbed as “joyful trains”. Even now, they can be seen serving as extra trains.