The SR Class 4DD was an experimental double-deckerelectric multiple unit built in 1949 and operated by the Southern Railway until 1971. Conceived by Oliver Bulleid for the Southern Railway's commuter line from London Charing Cross to Dartford, the two trains were the only double-decker trains to be used on the mainline railway network in Britain. Whilst commonly used in continental Europe and North America, the restrictive railway loading gauge in the United Kingdom prohibits normal double-decker trains with two fully separated decks.
The 4DD was more split-level than truly double-deck because the compartments were alternately high and low to ensure that the overall height of the train was exactly within the clearances necessary to safely pass through tunnels and under bridges. A mock-up was displayed at London Marylebone in 1949 shortly before it was first introduced into service,[1] but an assessment after one year in service revealed that the design would not be the optimum solution to the problems of overcrowding, nor would it help increase capacity, and the decision was made to extend trains from eight coaches to ten coaches by using regular, single-decker multiple units.[2]
A model of the SR Class 4DD
The intention to carry more passengers in a train of the same length as other contemporary stock was met, with the two 4-DD units having 1,104 seats compared to 800 in other units of similar age. However it was found that the additional number of passengers meant longer time spent at stations to allow passengers to get on and off.[2] In practice, the upper compartments were cramped and poorly ventilated because the upper-level windows were impossible to open due to tight clearance. To resolve this problem, the compartments were pressure-ventilated, but the equipment proved to be unreliable.
Near the end, they were renumbered 4901 and 4902. 4001 and 4002 were reassigned to another pair of prototype Southern Region four-coach EMUs, the 4-PEPs.
Unusually for an "experiment" they lasted in traffic from 1949 to 1971, undergoing routine maintenance and repaints with no hiccups in their life. The two units were finally withdrawn on 1 October 1971 having travelled approximately 700,000 miles in service.[2]
Formations
Key:
Scrapped
Preserved
Unit Numbers
DMBT
TT
TT
DMBT
Notes
Initial number
Final Number
4001
4901
13001
13501
13502
13002
(built September 1949)
4002
4902
13003
13503
13504
13004
(built October 1949)
Preservation
Driving motor cars 13003 and 13004 survive, the former at Kent Locomotives Ltd - Sellindge, Kent,[3] and the latter at the Northamptonshire Ironstone Railway Trust.[4] One trailer was also preserved, but it was scrapped when Ashford Steam Centre closed in 1984, in lieu of rent owed.[5] Driving motor car 13003 is now in the care of Bulleid 4-DD Double Deck EMU Group, which plans to restore it.[3]
References
^Archived at Ghostarchive and the : "Double-Deck Train (1949)". YouTube.
^ abc"Double-decker to go". News of the month. Railway World. Vol. 32, no. 378. Shepperton: Ian Allan. November 1971. p. 467.
^ ab"SR 13003 4-DD 'Double Decker' Driving Motor Brake Third built 1949". Vintage Carriages Trust. Retrieved 1 November 2017.
^"SR 13004 4-DD 'Double Decker' Driving Motor Brake Third built 1949". Vintage Carriages Trust. Retrieved 1 November 2017.
^Bright, Thomas (3 November 2017). "'O1' saviour Esmond Lewis-Evans dies". Steam Railway. Peterborough: Bauer Consumer Media (457): 18. ISSN 0143-7232.
Marsden, Colin J. (1983). Southern Electric Multiple-Units 1898–1948. Shepperton, Surrey: Ian Allan Limited. pp. 85–88. ISBN0-7110-1253-9.
Further reading
"Cash plea for Double-Decker EMU's 50th birthday rebuild". Rail. No. 345. EMAP Apex Publications. 2–15 December 1998. p. 63. ISSN 0953-4563. OCLC 49953699.
External links
Bulleid Double Decker Society
1949 British Pathe newsreel footage of the pre-production mockup
January 08, 2023
class, experimental, double, decker, electric, multiple, unit, built, 1949, operated, southern, railway, until, 1971, conceived, oliver, bulleid, southern, railway, commuter, line, from, london, charing, cross, dartford, trains, were, only, double, decker, tra. The SR Class 4DD was an experimental double decker electric multiple unit built in 1949 and operated by the Southern Railway until 1971 Conceived by Oliver Bulleid for the Southern Railway s commuter line from London Charing Cross to Dartford the two trains were the only double decker trains to be used on the mainline railway network in Britain Whilst commonly used in continental Europe and North America the restrictive railway loading gauge in the United Kingdom prohibits normal double decker trains with two fully separated decks Southern Railway 4 DDClass 4DD no 4902 in 1972In service1949 1971Constructed1949Number built2 sets 8 cars Number preserved2 DMBTsNumber scrapped2 DMBTs all TTsFormationDMBT TT TT DMBTFleet numberssee textCapacity552 seated 150 standing per set Operator s British RailLine s servedCharing Cross to DartfordSpecificationsTrain length257 ft 5 in 78 46 m Width9 ft 3 in 2 82 m Weight133 long tons 0 cwt 297 900 lb or 135 1 t Traction systemEnglish ElectricElectric system s 750 V DCCurrent collector s Third railBraking system s Electro pneumaticCoupling systemScrew linkTrack gauge4 ft 8 1 2 in 1 435 mm Contents 1 History 2 Formations 3 Preservation 4 References 5 Further reading 6 External linksHistory EditThe 4DD was more split level than truly double deck because the compartments were alternately high and low to ensure that the overall height of the train was exactly within the clearances necessary to safely pass through tunnels and under bridges A mock up was displayed at London Marylebone in 1949 shortly before it was first introduced into service 1 but an assessment after one year in service revealed that the design would not be the optimum solution to the problems of overcrowding nor would it help increase capacity and the decision was made to extend trains from eight coaches to ten coaches by using regular single decker multiple units 2 A model of the SR Class 4DD The intention to carry more passengers in a train of the same length as other contemporary stock was met with the two 4 DD units having 1 104 seats compared to 800 in other units of similar age However it was found that the additional number of passengers meant longer time spent at stations to allow passengers to get on and off 2 In practice the upper compartments were cramped and poorly ventilated because the upper level windows were impossible to open due to tight clearance To resolve this problem the compartments were pressure ventilated but the equipment proved to be unreliable Near the end they were renumbered 4901 and 4902 4001 and 4002 were reassigned to another pair of prototype Southern Region four coach EMUs the 4 PEPs Unusually for an experiment they lasted in traffic from 1949 to 1971 undergoing routine maintenance and repaints with no hiccups in their life The two units were finally withdrawn on 1 October 1971 having travelled approximately 700 000 miles in service 2 Formations EditKey Scrapped PreservedUnit Numbers DMBT TT TT DMBT NotesInitialnumber FinalNumber4001 4901 13001 13501 13502 13002 built September 1949 4002 4902 13003 13503 13504 13004 built October 1949 Preservation EditDriving motor cars 13003 and 13004 survive the former at Kent Locomotives Ltd Sellindge Kent 3 and the latter at the Northamptonshire Ironstone Railway Trust 4 One trailer was also preserved but it was scrapped when Ashford Steam Centre closed in 1984 in lieu of rent owed 5 Driving motor car 13003 is now in the care of Bulleid 4 DD Double Deck EMU Group which plans to restore it 3 References Edit Archived at Ghostarchive and the Wayback Machine Double Deck Train 1949 YouTube a b c Double decker to go News of the month Railway World Vol 32 no 378 Shepperton Ian Allan November 1971 p 467 a b SR 13003 4 DD Double Decker Driving Motor Brake Third built 1949 Vintage Carriages Trust Retrieved 1 November 2017 SR 13004 4 DD Double Decker Driving Motor Brake Third built 1949 Vintage Carriages Trust Retrieved 1 November 2017 Bright Thomas 3 November 2017 O1 saviour Esmond Lewis Evans dies Steam Railway Peterborough Bauer Consumer Media 457 18 ISSN 0143 7232 Marsden Colin J 1983 Southern Electric Multiple Units 1898 1948 Shepperton Surrey Ian Allan Limited pp 85 88 ISBN 0 7110 1253 9 Further reading Edit Cash plea for Double Decker EMU s 50th birthday rebuild Rail No 345 EMAP Apex Publications 2 15 December 1998 p 63 ISSN 0953 4563 OCLC 49953699 External links EditBulleid Double Decker Society 1949 British Pathe newsreel footage of the pre production mockup Retrieved from https en wikipedia org w index php title SR Class 4DD amp oldid 1129524951, wikipedia, wiki, book, books, library,
