British Rail Derby Lightweight

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British Rail Derby Lightweight
Derby Lightweight 79018 at Bewdley.JPG
Derby Lightweight power car no. 79018 on display at Bewdley on the Severn Valley Railway on 15 October 2004, as part of the Railcar 50 event. This vehicle has been restored to its original condition using a grant from the Heritage Lottery Fund, and is preserved at the Midland Railway - Butterley.
In service 1954-1969
Manufacturer BR's Derby Works
Number built 219 vehicles
Formation 1, 2 & 4 Car Formations
Operator British Rail
Maximum speed 62 mph (100 km/h)
Weight 27 tonnes (26.6 long tons; 29.8 short tons) power car
Traction system Mechanical
Prime mover(s) Two BUT
Power output (AEC) 125 bhp (93 kW) except BUT (AEC) 150 bhp (110 kW) for single units
Multiple working Yellow Diamond
Track gauge 1,435 mm (4 ft 8 12 in) standard gauge
Derby Lightweight trailer no. 975008 (79612) on display at Bewdley on the Severn Valley Railway on 15 October 2004, as part of the Railcar 50 event. This vehicle has yet to be restored to original condition, and is preserved at the Midland Railway - Butterley.

The British Rail Derby Lightweight diesel multiple units, were the first such trains to be built en-masse for British Railways. The units were built at BR's Derby Works from 1954 to 1955. The units were built in various formations, including 12 power-twin 2-car units, 84 power-trailer 2-car units, and four 4-car units. The two single car units were originally built as a two-car unit and then split two years later when demand came about. Contemporaneous with these units was the unique Battery Electric Multiple Unit.


The first units were introduced on services around the West Riding of Yorkshire, namely Leeds to Bradford services. Subsequent units were introduced onto services in Cumbria, Lincolnshire, Norfolk, and Birmingham to Sutton Coldfield, Bletchley to Buckingham and Banbury, and East London lines services. They were also the last units to run on the Anglesey Central Railway which closed to public traffic in 1964.

These units were an outstanding success, helping to reduce the operating costs of branchlines. As such, British Railways ordered many more DMU vehicles from various builders over the next decade, thus helping to eliminate steam locomotives. However, as these units were non-standard compared to other later DMU vehicles, they were subject to early retirement. The last units were withdrawn from normal traffic in 1969.


Four different sorts of formation were created from the 217 cars built of this type, as follows:

Power Twins[edit]

79000 + 79500 to 79007 + 79507
79184 + 79188 to 79189 + 79193

Power Trailers[edit]

79008 + 79600 to 79033 + 79625
79034 + 79250 to 79046 + 79262
79118 + 79639 to 79141 + 79662
79142 + 79684
79143 + 79663 to 79149 + 79669
79169 + 79670 to 79181 + 79682

Four Car Units[edit]

79150 79325 79400 79508
79151 79326 79401 79509
79152 79327 79402 79510
79153 79328 79403 79511
79154 79329 79404 79512

Single Car Units[edit]

79900 and 79901

79683 was left over as a spare DTCL, and took the place of 79649 in 1957, when this was converted into a special saloon. It was later renumbered 999510 in the departmental saloon series and was eventually scrapped in 1981.

In 1962 three of the power twin units were converted to power trailer units, when 79191-79193 were rebuilt as DTCL vehicles and renumbered 79633-79635.


Power Twins[edit]


  • Engine: Two BUT (AEC) 150 bhp
  • Transmission: Mechanical
  • Coupling code: Yellow diamond

Departmental Use[edit]

A number of cars from these units were subsequently transferred to departmental (non-revenue earning) use after withdrawal from normal service:

  • 79018 + 79612 were rebuilt as an ultrasonic test train based at Reading, numbered 975007 + 975008. Replaced by unit 901001.
  • 79900 was rebuilt as test coach "Iris", based at Bletchley, numbered 975010. Later transferred to the BR Research Division at the Railway Technical Centre at Derby, for its last few years in traffic, it was repainted into original BR Green livery. Replaced by unit 901002.
  • 79185 was taken into departmental use for brake trials, numbered 975012. It was scrapped in 1970.
  • 79250 and 79252 were taken into departmental use as staff messrooms, numbered 975013 and 975014. They were scrapped in 1978 and 1982 respectively.
  • 79649, the inspection saloon mentioned above, took its place in the departmental series as 999510.


Derby Lightweight single car unit no. 79900 fully restored to passenger carrying standard again after being former test car IRIS. The unit now resides on the Ecclesbourne Valley Railway running regular passenger diagrams.

Thanks to their extended life in departmental service, one 2-car unit and a single car unit survive in preservation, the former following a high-profile campaign.

Vehicle Nos. Location Comments In Service Departmental Nos.
79018 79612 Ecclesbourne Valley Railway Used as ultrasonic test train. Part Restored/Not In Service 975007 975008
79900 - Ecclesbourne Valley Railway Used as test coach "Iris". Regularly in Passenger Service 975010 -
79998 79999 Royal Deeside Railway fitted with test equipment operational

External links[edit]

Media related to British Rail Derby Lightweight at Wikimedia Commons