The classes EF52, EF53, EF56 and EF57 were electric 2-C+C-2 passenger locomotives built by various manufacturers for the Japanese Government Railways between 1928 and 1940. They were used on the Tokaido and Yokosuka lines which had been electrified with 1,500 Volts DC. They initially had an output of 1,350 kW and a top speed of 95 km/h. Between the individual classes, many improvements were introduced and the gear ratio had been modified for increased pulling power at speed, without changing the top speed. The EF57 introduced in 1940 had an output of 1,650 kW. With the introduction of more modern locomotives like the EF58, some got their steam heating boilers removed in change for electric train heating and were transferred to other lines. Most were withdrawn in the seventies, but some which had been rebuilt survived until the late eighties.