British Rail Class 121

British Rail Class 121
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W55033 at the Colne Valley Railway in original green livery
In service1960 - present
ManufacturerPressed Steel Company
Family nameBubble Car
Number built16
Formation1 car per trainset
Operator(s)Arriva Trains Wales

Chiltern Railways

Network Rail
Specifications
Car length64 ft 6 in (19,660 mm)
Width9 ft 3 in (2,820 mm)
Height12 ft 4 in (3,760 mm)
Maximum speed70 mph (110 km/h)
Weight38 tons
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Sixteen Class 121 single-car driving motor vehicles were built from 1960, numbered 55020-55035. These were supplemented by ten trailer vehicles, numbered 56280-289 (later renumbered 54280-289). They had a top speed of 70 mph, with slam-doors, and vacuum brakes. The driving motor vehicles were nicknamed "Bubble Cars" by some enthusiasts.