british rail class 315 alternating current (ac) electric multiple units (emu) were built by brel at york works from 1980 to 1981. they were the fifth and final 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). like the glasgow-based class 314 units, they are only able to operate from 25 kv overhead line current collection. the fleet works inner-suburban services on the great eastern main line run by the train operating company tfl rail out of london liverpool street. class 315s also work services from liverpool street to chingford, enfield town and cheshunt operated by london overground.