British Rail Class 122

The British Rail Class 122 diesel mechanical multiple units were built by Gloucester RC&W in 1958. Twenty single-car, double-ended driving motor vehicles, nicknamed "Bubble Cars", were built, numbered 55000–55019. These were supplemented by nine single-ended trailer vehicles, numbered 56291–56299 (some of which were later renumbered into the 54291–54299 block).

Initial use
The Class 122s were built mainly for use on the London Midland Region of British Rail, although some were also used in Scotland. They were used on a variety of lightly used lines, many of which were closed during the Beeching Axe in the 1960s. Routes served included the Stourbridge Town and St Albans Abbey branch lines, as well as local services between Dundee and Arbroath. (The similar Pressed Steel Company built Class 121 single units were used on the Western Region). These were replaced by Class 150s, 153s and spare cascaded fleet.

Parcels use
Three Scottish Region cars (55013–55015) were converted to carry parcels traffic and were reclassified Class 131, though the vehicles themselves were not renumbered.

Usage after passenger service
Upon privatisation of Britain's railways, the Class 122 fleet has been withdrawn from normal service. However several units were operated by EWS and Network Rail (previously Railtrack) in departmental service, reclassified as Class 960.

Preservation
"Bubble Cars" have proved popular for preservation on heritage railways.