british rail class 314 alternating current (ac) electric multiple units (emu) were built by brel at york works from 1978 to 1979. they were the second 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). able to operate from 25 kv overhead line current collection only, the fleet worked outer-suburban services on the strathclyde passenger transport rail network in central scotland.