British United Traction
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| Industry | Bus manufacturing |
|---|---|
| Founded | 1946 |
| Defunct | 1964 |
| Owner | AEC Leyland |
British United Traction (BUT) was a manufacturer of railway equipment and trolleybuses. It was established in 1946 as a joint venture between AEC and Leyland.
History
British United Traction was established in 1946 when AEC and Leyland amalgamated their trolleybus interests. Neither had produced trolleybuses since the early years of World War II. With both forecasting that demand would return to pre-war levels as networks began to close, a joint venture was formed. The new company was organised so that AEC would design and produce vehicles for the UK market while Leyland looked after export markets, although there were some exceptions to this. The only noticeable difference between the manufacturers' output was the wheels.
Initially vehicles were produced at Leyland's Ham, London factory, with the first vehicles completed in 1947 for Johannesburg. After the factory closed 1948, production moved to AEC's Southall and Leyland's Leyland, Lancashire factories. Following AEC's acquisition of Crossley Motors, AEC transferred its production to the latter's Stockport factory. Trolleybus production wound down in the late 1950s, however a final batch for Wellington was built at Scammell's, Watford factory in 1964.
Trolleybuses
Diesel engines for railways
 | This section does not cite any sources. (July 2018) |
British United Traction was a major supplier of diesel engines for British Rail's first-generation diesel multiple units. These engines were built in 125Â hp (93Â kW) or 150Â hp (110Â kW) versions and were branded BUT, although manufactured by BUT's parent companies, AEC and Leyland. There was also a 230Â hp (170Â kW) BUT engine, manufactured by Albion, a Layland subsidiary.
A 275Â hp (205Â kW) version was supplied to the Ulster Transport Authority for its UTA MPD class railcar.
BUT / ACV railcars
| BUT / ACV railcars | |
|---|---|
| In service | 1952â1960 |
| Manufacturer | British United Traction Associated Commercial Vehicles (AEC, Park Royal Vehicles) |
| Order no. | List
|
| Family name | First generation |
| Replaced | Steam locomotives and carriages |
| Constructed | 1952, 1955â1957 |
| Scrapped | 1963 |
| Number built | 3 DMT/DMS, 4 DMBT/DMBS, 4 TT/TS |
| Number scrapped | All |
| Formation | 1-, 2-, or 3-car sets |
| Capacity | DMT/DMS: 41 (prototype car), 34 (production cars) DMBT/DMBS: 28 TT/TS: 48 |
| Operators | British Rail |
| Depots | Watford |
| Specifications | |
| Car length | 37Â ft 6Â in (11.43Â m) |
| Width | 9Â ft 0Â in (2.74Â m) |
| Height | 11Â ft 4Â in (3.45Â m) |
| Wheelbase | 22Â ft 0Â in (6.71Â m) |
| Maximum speed | 45Â mph (72Â km/h) |
| Weight | 15 long tons (15Â t) (motor cars), 10.5 long tons (10.7Â t) (trailers) |
| Prime mover(s) | AEC 6-cylinder diesel, one per motor car |
| Power output | 125Â bhp (93Â kW) each engine |
| Transmission | Mechanical: 4-speed epicyclic gearbox |
| Coupling system | Screw-link couplings |
| Track gauge | 4 ft 8+1â2 in (1,435 mm) |
In 1952, British United Traction introduced a prototype diesel-mechanical multiple unit as a demonstrator. This was followed by orders for production units built from 1955 to 1957. The units were designed by BUT and constructed by Associated Commercial Vehicles group companies, with underframes and engines by AEC and bodies by Park Royal Vehicles. Instead of bogies, each vehicle had a two-axle four-wheel arrangement. The demonstrator unit was introduced as a 3-car set with two motor cars and a centre trailer car. In addition to operating as either a 3 or 2-car set, each motor car was equipped with driving controls at both ends and could operate as single-car units, with a similar configuration to the later British Rail railbuses.
Operations
The demonstrator unit underwent a series of trials across all regions of British Railways, often on low revenue routes. The first trials were operated between Didcot and Newbury, followed by trials on High Wycombe-Princes Risborough, Epping-Ongar, Watford-St Albans, Chalfont & Latimer-Chesham, Bangor-Amlwch, Ayr-Dalmellington, Hull-South Howden, Birmingham-Solihull, Gravesend-Allhallows-on-Sea, Wellingborough-Higham Ferrers and Harrow-Belmont services.
BR acquired the set in 1955, together with a second 3-car set and a spare motor car and trailer. Under BR ownership, these units worked on regular Watford-St Albans services. A third 3-car set was delivered in 1957 and operations were expanded to include regular Harrow-Belmont services.
Withdrawal
The units were unreliable in regular service, and were noted for their poor ride quality. By 1961, all vehicles had been moved to Derby Friargate for storage. No other use could be found for them, and all units were subsequently withdrawn and scrapped at Derby C&W Works by 1963.
Fleet details
| Lot No. | Type | Diagram | Qty | Fleet numbers | Notes |
|---|---|---|---|---|---|
| 30128 | Driving Motor Third (DMT) | 500 | 1 | 79740 | 41 seats |
| 30128 | Trailer Third (TT) | 500 | 1 | 79741 | 48 seats |
| 30128 | Driving Motor Brake Third (DMBT) | 500 | 1 | 79742 | 28 seats |
| 30174 | Driving Motor Brake Third (DMBT) | 506 | 2 | 79743-79744 | 28 seats |
| 30175 | Driving Motor Third (DMT) | 506 | 1 | 79745 | 34 seats |
| 30176 | Trailer Third (TT) | 506 | 2 | 79746-79747 | 48 seats |
| 30214 | Driving Motor Second (DMS) | 506 | 1 | 79748 | 34 seats |
| 30215 | Trailer Second (TS) | 506 | 1 | 79749 | 48 seats |
| 30216 | Driving Motor Brake Second (DMBS) | 506 | 1 | 79750 | 28 seats |
| Industry | Bus manufacturing |
|---|---|
| Founded | 1946 |
| Defunct | 1964 |
| Owner | AEC Leyland |
Last updated 24 June 2025. All information and images sourced from the relevant Wikipedia article(s) unless stated otherwise. If any information is incorrect, please let us know by emailing us: [email protected]. Text is available under the Creative Commons Attribution-ShareAlike License 4.0; additional terms apply.