A single PEP prototype two-car set and two four-car sets were extensively tested and evaluated on the Southern Region in the early 1970s, resulting in a new fleet of trains for BR suburban services. From 1976, when Class 313s were introduced, they became a common sight on many urban rail networks. Although their numbers have been eroded in many areas, with one class technically extinct, they remain in daily service in parts of England.
They differ from Mk.1 EMUs in having a flatter roof