The British Rail Class 313 is a dual-voltage electric multiple unit (EMU) train built by British Rail Engineering Limited's Holgate Road carriage works between February 1976 and April 1977. They were the first variety of British Rail's then-standard 1972 design for suburban EMUs, which eventually encompassed 755 vehicles and five classes (Class 313/314/315/507/508). They were the first second-generation EMUs to be constructed for British Rail and the first British Rail units with both a pantograph for 25 kV AC overhead lines and shoegear for 750 V DC third rail supply. They were the first units in Britain to have multi-functional Tightlock couplers, allowing the coupling and the connection of controlled electrical and air supplies to be carried out from the cab.