By the mid-1950s, increasing competition from road vehicles continued to reduce passenger numbers on many rural land branch railway services. Lightweight diesel units offered the railways a reliable, economical alternative to steam traction on low-density routes. The Class 122, introduced in 1958, was designed specifically to meet this requirement by providing a self-contained, single-unit vehicle capable of operating efficiently on lightly used lines without the need for a locomotive or additional crew.
Drawing on proven technology from the road transport sector, the Class 122 employed compact underfloor diesel engines similar in principle to those used in contemporary buses. This approach allowed British Railways to deliver a unit that was cleaner, faster to start, cheaper to maintain, and more responsive for short-distance stopping services. The low rolling resistance of steel wheel on rail meant that modest power output was sufficient to achieve brisk acceleration and competitive journey times compared with steam traction previously used on the same duties.
The Class 122 “Bubble Car” quickly proved successful on branch line, suburban, and feeder services across several regions. Its simple mechanical layout, quick turn-round capability, and ability to operate independently or in multiple with other units made it a highly flexible and economical solution for local passenger operations.
PACK FEATURES
● Wobbly speedo
● Bubble Car plus Trailer Car and Parcels variants.
● Custom particle effects
● Changeable destination blind
● Automatic Driver changeover
● Lighting & weather effects
● Passengers
● Quick Drives
● 2 Scenarios for Falmouth and Riviera in the 1950s
● Passenger view
TECH DETAILS
● Power Type: Diesel-Mechanical
● Engine: 1 × BUT/AEC or Leyland 150–180 hp underfloor engine
● Transmission: Mechanical, 4-speed epicyclic gearbox
● Unit Weight: Approx. 30–32 tons (driving trailer slightly lighter)
● Vehicle Length: 64 ft 6 in over buffers
● Build Date: 1958
● Maximum Speed: 70 mph
● Multiple Working: Compatible with Class 116/117/118 era units (Blue Square
system)
● Passenger Capacity: Approximately 65 seats depending on internal layout
● Fuel Capacity: Approx. 300 gallons
● Construction: Steel-bodied, with driving cab at one end and guard/luggage space
incorporated as required
● Total Built: 20 driving motor cars + 10 driving trailers
● Preservation: Multiple examples preserved and operational on heritage railways
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