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.
Class 122, no. 55006, at Bewdley on the Severn Valley Railway on 15 October 2004, whilst taking part in the Railcar 50 event. This unit is painted in the second version of BR Green livery, and is preserved on the Ecclesbourne Valley Railway.
Interior of W55000 on the South Devon Railway
The British Rail Class 121 is a single-car double-ended diesel multiple unit. 16 driving motor vehicles were built from 1960, numbered 55020–55035. These were supplemented by ten single-ended trailer vehicles, numbered 56280–56289. They have a top speed of 70 mph (113 km/h), with slam-doors, and vacuum brakes. The driving motor vehicles were nicknamed "Bubble Cars" by some enthusiasts.
A Class 121 at Reading in 1992
Interior of 121032
Preserved W55033 at the Colne Valley Railway in original green livery, with yellow "speed whiskers" (warning stripes) on the cab front. This unit differs from the rest of the class by the fitment of a small route indicator box above the centre window, like a Class 122, rather than a large headcode box.
121020 and 121034 at Bewdley in 2004.
