British Rail Derby Lightweight

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British Rail Derby Lightweight
Derby Lightweight 79018 at Bewdley.JPG
Derby Lightweight power car no. 79018 at Bewdley on the Severn Valley Railway
In service1954-1969
ManufacturerBR Derby Works
Number built217 vehicles
Formation1, 2 & 4 Car Formations
Capacity16 1st + 53 3rd class (motor composite), 61 3rd class (motor third brake)
Operator(s)British Rail
Car length57 ft 6 in (17.53 m)
Doors2 on each side
Maximum speed62 mph (100 km/h)
Weight27 tonnes (26.6 long tons; 29.8 short tons) power car
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 gauge1,435 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 is being restored to original condition, is complete externally, and the twin unit is preserved at the Ecclesbourne Valley Railway - Wirksworth.

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.

Body framing was extruded and riveted together. Panelling was welded into continuous sheets and riveted to the frame. Luggage racks were light alloy. The floors had 2 layers of flameproof hardboard, covered with linoleum. To reduce noise and condensation, the inside structure and undersides were sprayed with asbestos. Lighting was by 60-watt, 24-volt lamps charged by belt driven dynamos. Heating was oil fired. Standard mild steel bogies ran on Timken roller bearings.[1]

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 and Harrogate services from 14 June 1954.[2] Subsequent units were introduced onto services in West Cumbria, Lincolnshire, Norfolk, Newcastle to Middlesbrough, Edinburgh to Glasgow[3] and, later, 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. Initially they also attracted many more passengers. Between February and October 1956 on the London Midland, they carried 800,000 more passengers than steam in the same period of 1955. The largest increase was 434% (4,772 passengers) on the Buckingham-Banbury line (from 13 August), followed by Birmingham-Lichfield 178% (from 5 March), Bury-Bacup 152% (from 6 February), Llandudno-Blaenau Ffestiniog 39% (from 5 March) and Manchester-Buxton 38% (from 8 October).[4] 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.

Table of orders and numbers
Lot No. Type Diagram Qty Fleet numbers Notes
30084 Driving Motor Brake Second (DMBS) 501 8 E79000–79007 ER Power Twin sets
30085 Driving Motor Composite with lavatory (DMCL) 507 8 E79500–79507 ER Power Twin sets
30123 Driving Motor Brake Second (DMBS) 503 13 M79008–79020 LMR Power-Trailer sets
30124 Driving Trailer Composite with lavatory (DTCL) 509 13 M79600–79612 LMR Power-Trailer sets
30126 Driving Motor Brake Second (DMBS) 504 13 M79021–79033 LMR Power-Trailer sets
30127 Driving Trailer Composite with lavatory (DTCL) 505 13 M79613–79625 LMR Power-Trailer sets
30177 Driving Motor Brake Second (DMBS) 504 13 M79034–79046 LMR Power-Trailer sets
30178 Driving Trailer Composite with lavatory (DTCL) 505 13 M79250–79262 LMR Power-Trailer sets
30192 Driving Motor Composite (DMC) 502 5 E79508–79512 ER 4-car sets
30193 Driving Motor Second (DMS) 508 5 E79150–79154 ER 4-car sets
30194 Trailer Brake Second with lavatory (TBSL) 517 5 E79325–79329 ER 4-car sets
30195 Trailer Second with lavatory (TSL) 518 5 E79400–79404 ER 4-car sets
30201 Driving Motor Brake Second (DMBS) 633 7 M79143–79149 LMR Power-Trailer sets
30202 Driving Trailer Composite with lavatory (DTCL) 642 7 M79663–79669 LMR Power-Trailer sets
30235 Driving Motor Brake Second (DMBS) 633 9 M79118–79126 LMR Power-Trailer sets
30236 Driving Trailer Composite with lavatory (DTCL) 509 9 M79639–79674 LMR Power-Trailer sets
30240 Driving Motor Brake Second (DMBS) 633 10 M79127–79136 LMR Power-Trailer sets
30241 Driving Trailer Composite with lavatory (DTCL) 509 10 M79648–79657 LMR Power-Trailer sets
30240 Driving Motor Brake Second (DMBS) 527 4 E79137–79140 ER Power-Trailer sets
30241 Driving Trailer Composite with lavatory (DTCL) 631 4 E79658–79661 ER Power-Trailer sets
30246 Driving Motor Brake Second (DMBS) 633 2 M79141–79142 LMR Power-Trailer sets
30247 Driving Trailer Composite with lavatory (DTCL) 642 1 M79662 LMR Power-Trailer sets
30321 Driving Motor Brake Second (DMBS) 633 13 M79169–79181 LMR Power-Trailer sets
30322 Driving Trailer Composite with lavatory (DTCL) 511 15 M79670–79684 LMR Power-Trailer sets
30324 Driving Motor Brake Second (DMBS) 633 5 M79184–79188 LMR Power Twin sets
30325 Driving Motor Composite with lavatory (DMCL) 509 5 M79189–79193 LMR Power Twin sets
30380 Driving Motor Brake Second (DMBS) 514 1 M79900 Single car unit; 61 seats
30387 Driving Motor Brake Second (DMBS) 515 1 M79901 Single car unit; 52 seats


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

Power Twins[edit]

8 79000 + 79500 to 79007 + 79507
5 79184 + 79189 to 79188 + 79193

Power Trailers[edit]

26 79008 + 79600 to 79033 + 79625
13 79034 + 79250 to 79046 + 79262
24 79118 + 79639 to 79141 + 79662
1 79142 + 79684
7 79143 + 79663 to 79149 + 79669
13 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]


79683 was left over as a spare DTCL, and took the place of 79649 in 1957, when this was converted into a special saloon on diagram 565. 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 79000+79500 to 79007+79507[edit]

Remainder of the fleet[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

See also[edit]

  • British Rail BEMU – a power-trailer two car EMU based on the Derby Lightweight DMU design.


  1. ^ Cooke, B.W.C., ed. (July 1954). "Lightweight Diesel Trains for British Railways". The Railway Magazine. Vol. 100 no. 639. Westminster: Tothill Press. p. 461.
  2. ^ Cooke, B.W.C., ed. (June 1954). "B.R. Lightweight Diesel Trains". The Railway Magazine. Vol. 100 no. 638. Westminster: Tothill Press. p. 369.
  3. ^ Cooke, B.W.C., ed. (July 1954). "Lightweight Diesel Trains for British Railways". The Railway Magazine. Vol. 100 no. 639. Westminster: Tothill Press. p. 458.
  4. ^ Railway Magazine February 1957 p. 74

External links[edit]

Media related to British Rail Derby Lightweight at Wikimedia Commons