The AEC Regent III RT was a variant of the AEC Regent III. It was a double-decker bus produced jointly between AEC and London Transport. It was the standard red London bus during the 1950s.
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The prototype
The prototype (London Transport RT 1) was built in 1938 with AEC's 8.8-litre engine (a stopgap measure until the new 9.6-litre was available) and air-operated pre-selective gearbox. The air compressor was bought from Bosch, and this was to cause headaches at AEC in the following months. Somewhat surprising, and a choice which can only be described as deliberately misleading, was the decision to place the prototype in service disguised as an old vehicle. It carried a secondhand open-staircase body previously carried on Leyland Titan TD 118. RT 1 entered service in November 1938 as ST 1140 even though it was nothing like a standard ST vehicle. It continued in service until February 1939, apparently without attracting the attention of the technical press. It would be difficult to imagine the same sort of success today, as it carried the then new registration number EYK396 giving a good clue to its age. While the chassis was on trial a new body was constructed at London Transport's Chiswick works. Its four-bay body resembled that of the conventional Roe body exhibited at the 1937 Commercial Motor Show, though the overall impression of modern design and the features included marked a big step forward. No-one could have foreseen that it would be another 40 years before the last RT-type bus was retired by London Transport, in 1979.
Pre-war production vehicles
London Transport ordered 338 (later cut to 150) chassis which were in production when the war broke out in September 1939. The last of the batch, RT 151, did not reach London Transport until January 1942. The only other RT-type chassis constructed before the end of the war was destined for Glasgow, originally intended to be an exhibit at the 1939 Commercial Motor show, but cancelled due to the outbreak of war. It differed from the pre-war London examples in having a body built by Weymann, though the cab area was very similar to the London vehicles.
Post-war production vehicles
Production of the RT recommenced in late 1946. The new vehicles were built to a modified version of the pre-war London Transport design and were similar in appearance to their predecessors. The main visual differences were:
- The ultimate (narrow) destination blind was now located just above the driver with the via blind (wide) between the ultimate and the top deck windows.
- The front route number remained above the top deck windows (known by some as the lighthouse box...as well as the more widely used roofbox) although the rear one was removed and the route number joined the 'via' points in the main display.
- The bodywork was constructed by contractors rather than by London Transport.
- The lower edge of the cab window forward of the driver's door and the lower edge of the driver's windscreen were horizontal, whereas on pre-war examples they curved downwards towards the corner of the cab.
- The number of ventilation slats below the windscreen was reduced from 6 to 4.
London Transport received 4674 post-war RT-type buses between 1947 and 1954, and a small number of similar buses were sold to operators outside London.
