British Rail Class 377

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British Rail Class 377 "Electrostar"
Southern 377 at Hemel Hempstead.JPG
Southern Class 377/2 no. 377207 at Hemel Hempstead with a service from Milton Keynes Central to East Croydon
SOUTHERN 377401 STD CLASS Interior.jpg
The interior of Standard Class in a DMCO vehicle in Bombardier Classes 377/4 and 377/5
In service May 2003 - Current
Manufacturer Bombardier Transportation, Derby
Family name Electrostar
Number built 211 trainsets (excluding 28 375/3 conversions)
Number in service 239 trainsets
  • 377/1/2/4/5: 4 cars per set (DMOC-MOC-PTOS-DMOC)
  • 377/3: 3 cars per set (DMOC-PTOS-DMOS)
  • 377/6/7: 5 cars per set (DMOC-MOS-PTOS-MOS-DMOS)
Car length 20.4 m (66 ft 11 18 in)
Width 2.80 m (9 ft 2 14 in)
Height 3.78 m (12 ft 4 78 in)
Maximum speed 100 mph (161 km/h)
  • 173.6 t (170.9 long tons; 191.4 short tons) (377/1, /2, /4, /5)
  • 133.1 t (131.0 long tons; 146.7 short tons) (377/3 only)
Power output
  • 1.2 megawatts (1,600 horsepower) (377/1, /2, /4, /5)
  • 0.8 megawatts (1,100 horsepower) (377/3 only)
Electric system(s)
Current collection method
Multiple working within class and with British Rail Class 387[citation needed]
Track gauge 1,435 mm (4 ft 8 12 in) standard gauge

The Class 377 Electrostar is a British electric multiple-unit train (EMU) built by Bombardier Transportation at its Derby Works, from 2001 to the present. The Electrostar family is the most numerous type of EMU built in the post-privatisation period of Britain's railways.

The class forms the major part of the Govia Thameslink Railway (GTR) fleet for Southern and Thameslink services. They are primarily seen on services in the south of England.


The units work suburban services in South London, and main line commuter services to Sussex, Surrey, Kent and the South Coast, on which they replaced 4Cig and 4Vep slam-door stock which came to end of their useful lives and which did not meet modern health and safety requirements. Built in the early 2000s, the units had a troubled introduction; being fully air-conditioned, their higher power consumption compared to the slam-door Mark 1-based stock that they replaced led to major upgrades being required to the 750 V DC third-rail power supply used in the former Southern region.[1] The collapse of Railtrack following the Hatfield accident further delayed this upgrade work, and the new stock did not enter squadron service until 2003.

Class 377s are fitted with external CCTV. There is a disabled seating area, and both intermediate coaches have toilets. Bodyside power doors are electrically operated, a move away from the air powered systems of previous generation EMUs. Dual-voltage units are fitted with a Brecknell Willis high-speed pantograph, incorporating a pair of aerofoils on the pan knuckle to steady the pan head against the OLE contact wire. The configuration of a 5-car Class 377 unit is:

  • DMOC(A) - 2 motors on inner bogie, sander, auxiliary converter module
  • MOSL - 2 motors on inner bogie, standard toilet
  • PTSOL - pantograph, transformer, compressor, disabled toilet
  • MOS - 2 motors on inner bogie, standard class interior (only found on Class 377/6 and 377/7 units)
  • DMOS(B) - 2 motors on inner bogie, sander, auxiliary converter module

In 4-car units the driving cars are composite, with the first-class saloon between the driving cab and the first set of passenger doors. 4-car units also do not contain the MOS coach.


Mitrac is the Bombardier Train Management System (TMS). It provides monitoring of on-train systems, fault-finding diagnostics, event monitoring, and preventative maintenance. In conjunction with the onboard GPS receiver, Mitrac controls Selective Door Operation (SDO), as well as automatic Passenger Information System (PIS) displays and Public Address announcements. Engineers can access the system remotely via GSM to download the fault log, then carry out real-time diagnostics while the train continues in service.


The Class 377 uses Dellner[2] couplers instead of the Tightlock type originally used on Southern's Class 375s. Southern's 375s were all converted to Class 377/3s - these reclassified units can still be identified by their 3-car formation. Note that Southeastern's 375s (sub-classes 375/3, 375/6, and 375/7) were also converted to Dellner couplers, but not reclassified; its 375/8 and 375/9 units were fitted with Dellner couplers as built.[3]

Traction current supply[edit]

All units can receive power via third-rail pick-up which provides 750 V DC. There are eight pick-up shoes per unit (twice the number of previous generation 4-car Electric multiple units), and this enables them to ride smoothly over most third-rail gaps. The units in the 377/2, 377/5 and 377/7 sub-classes are dual-voltage, and are fitted with a pantograph to pick up 25 kV AC from overhead lines. On these units the shoe mechanism is air-operated so that when powered down, or working on AC overhead lines, they are raised out of the way. This is used on trains from Milton Keynes to East Croydon which use part of the West Coast Main Line between Milton Keynes and Willesden Junction, and then the West London Line towards Clapham Junction. These trains change to third-rail DC supply on a dual-voltage section of the West London line north of Shepherd's Bush.[4] Since March 2009, dual-voltage Class 377 sets have also been operating some Thameslink Bedford to Brighton, Rochester and Ashford services. (See below).

Among the remaining units, the trailer coach in each unit has a recess in its roof where a pantograph could be fitted, to allow for future conversion to overhead AC power. Despite most units being DC-only, the class is numbered in the 3xx series normally used for AC units.

Additional units and the Thameslink Programme[edit]

In April 2007, as part of the Route Utilisation Strategy for the Brighton Main Line, it was announced that Southern would procure an additional 48 Class 377 carriages to replace an identical number of Class 319 carriages (12 4-car units) due to be transferred to First Capital Connect.[5] Eleven further dual-voltage units were then added to the order, making a total of 23. They were ordered from Bombardier in March 2008 and were delivered in First's corporate colour scheme but with Southern spec interior (green seats).[6] The units were commissioned at Southern's Selhurst depot in Croydon before being transferred to First Capital Connect's Bedford Cauldwell depot. The first of these, unit 377501, was delivered to Cauldwell depot on 27 February 2009 after making its first appearance through the Thameslink Central London core. The 377/5s operate mainly on Bedford to Brighton services but in the peaks form part of FCC's and Southeastern's new joint service to places such as Rochester and Ashford. Once FCC's new passenger vehicles come into service, the 377/5 fleet will be returned to Southern.

Delays in the construction of the Class 377/5s for First Capital Connect saw the temporary transfer of eight of Southern's Class 377/2s to FCC to enable them to implement the planned timetable changes on 22 March 2009; the loss of these units until September 2009 was covered by the temporary cascade of a number of Class 350/1s to Southern from London Midland, which operated services between East Croydon and Milton Keynes.[7]

In September 2011 it was announced that Southern had begun the procurement of 130 vehicles, due to delays in the procurement of new Thameslink rolling stock that would prevent transfer of the 377/5s in time for the December 2013 timetable change.[8] The contract was awarded to Bombardier in December 2011.[9][10] The additional eight five-car units (from an option in the contract for 40 additional vehicles) are dual-voltage and known as Class 377/7.[11]

In December 2011 three Class 377/2 units were transferred from Southern to First Capital Connect (now Thameslink) to allow more 12-car services to be run.

During mid-2013 the first of the new class 377/6s arrived from Derby for type testing, and since October 2013 these units have been used in passenger service, initially on a peak-hours London Bridge-West Croydon diagram. The /6 subclass has clear external differences from the previous subclasses, notably windows set in frames instead of the more expensive ribbon glazing of earlier units.

Southern liveried Bombardier Class 377/1 Electrostar No. 377122 is seen departing Warnham, with a service bound for Horsham
Southern liveried Bombardier Class 377/2 Electrostar No. 377213 at Watford Junction, with a service bound for Brighton
Southern liveried Bombardier Class 377/4 Electrostar No. 377448 at Tinsley Green
Thameslink Bombardier Class 377/5 Electrostar No. 377508 is seen arriving at St. Albans, with a southbound service for Brighton
Southern-liveried Bombardier Class 377/6 Electrostar 377604 about to depart at London Victoria platform 9 with a Sutton service

Southeastern are expected to receive 25 Class 377 units in coming years according to Department for Transport documents published in September 2013, relating to the new combined Thameslink, Southern and Great Northern Franchise.[12]

Current operations[edit]


  • Mainline and Redhill Routes: London to Brighton, Horsham, Reigate, Tonbridge, Eastbourne, Ore, Portsmouth, Southampton, Littlehampton, Bognor Regis
  • East Coastway: Brighton to Eastbourne, Hastings and Ore
  • West Coastway: Brighton to Portsmouth, Littlehampton, Bognor Regis and Southampton
  • West London Line: East Croydon to Milton Keynes Central
  • Oxted Line: London to East Grinstead
  • Outer Suburban services: Central London to Tattenham Corner, Horsham, Dorking, Guildford (selected workings)
  • Inner Suburban services: Central London to Caterham, Sutton, Epsom, Epsom Downs, West Croydon, Beckenham Junction via Crystal Palace (selected workings)


  • Thameslink: (Brighton-Gatwick Airport-London-Luton-Bedford also Bedford to Ashford/Rochester in peak hours)

Future Operations[edit]


Southeastern are expected to receive 25 Class 377/1 Southern units in 2017 according to Department for Transport documents published in September 2013, relating to the new combined Thameslink, Southern and Great Northern Franchise.[12]

Aborted Proposals[edit]

Great Northern[edit]

Beginning 2016, 19 of the 23 Class 377/5 units were planned to be transferred for use on non-stop London-Cambridge services, however it has since been decided that the 29 Class 387/1s currently operating on Thameslink will be used instead.[13]

Fleet details[edit]

Class Operator No. Built Year Built Cars per Set Unit nos. Notes
Class 377/1 Southern 64 2002–2003 4 377101-164 All 3rd rail routes.
Class 377/2 Southern 6 2003–2004 4 377201-206 Dual-voltage units.
These are used on the East Croydon - Milton Keynes Central route as well as Metro routes in South London and occasionally main line workings to the South Coast.
377207-377215 are on loan to Thameslink until the new Thameslink stock arrives.
Thameslink 9 377207-215
Class 377/3 Southern 28 2001–2002 3 377301-328 3-car units converted from Class 375 Nos. 375311-338 by having their Tightlock couplers replaced by Dellners.
Originally used on Coastway services but have now moved to London suburban services, being replaced by Class 313s.
Class 377/4 Southern 75 2004–2005 4 377401-475 All 3rd rail routes.
Units 377472 and 377474 had 'speed run' branding in reference to these units having formed the record breaking London to Brighton run. This branding was removed upon overhaul in late 2014.
Class 377/5 Thameslink 23 2008–2009 4 377501-523 23 dual-voltage units ordered by Southern. Transferred to Thameslink as part of the Thameslink Programme Key Output Zero (KO0).
Class 377/6 Southern 26 2012-2013 5 377601-626[11] All 3rd rail routes.
Ordered as replacement for the three 377/2 and twenty-three 377/5 units on loan from Southern to Thameslink. The trains on loan to Thameslink won't be returned in time for lengthening services via Balham from 8 to 10 carriages.
The Class 456 fleet was subsequently transferred to South West Trains.[14]
All trains have now entered service on the metro routes with some workings on the Brighton Main Line.
Class 377/7 Southern 8 2014 5 377701-708[11] Additional 8 dual-voltage units. 377701-377708 have entered service on metro services and on the East Croydon - Milton Keynes Central services.[15] The option for 40 new vehicles from Bombardier appears in the manufacture and supply agreement for the order of 130 Electrostar vehicles from Bombardier announced by Southern on 28 December 2011. The MSA provides that the option for the further 40 vehicles expires on 31 December 2012. The 40 vehicles were built in 5-car formation with dual voltage configuration, costing circa £60 million in total, and they were delivered during 2014 for service entry in December of that year.


Southern Class 377 Diagram.PNG
Class 377 First Capital Connect Diagram.PNG

London-Brighton Speed Record[edit]

On 11 September 2005, units 377472 and 377474 set the record for a London Bridge to Brighton run of 36 minutes 56 seconds.[16]


  1. ^ Ford, Roger (May 2003). "SR power upgrade agreements signed". Modern Railways. London. 
  2. ^ "Dellner Couplers AB — Automatic and Semi-Permanent Couplers". Retrieved 10 October 2014. 
  3. ^ "Southern Electric Fleet Review Summer 2004". Southern Electric Group. 21 April 2006. 
  4. ^ Jacobs, G. (ed) (2008). Railway Track Diagrams 5: Southern and TfL (3rd edition). Bradford-on-Avon: Quail. p. 1R.
  5. ^ "More trains arriving on busy rail routes". Department for Transport. 4 April 2007. Archived from the original on 5 July 2007. 
  6. ^ Photograph of 377501
  7. ^ "All Aboard for the latest game of musical trains on the National Network" (PDF). Railway Herald (169). Scunthorpe. p. 4. 
  8. ^ "Could Southern be the lifeline for Bombardier?" (PDF). Railway Herald (284). Scunthorpe. p. 3. 
  9. ^ "Boost for Derby as Bombardier wins Southern order". Railnews. 28 December 2011. Retrieved 9 January 2012. 
  10. ^ "DfT acts to ease Thameslink trains logjam". Railnews. 16 November 2012. Retrieved 16 November 2012. 
  11. ^ a b c Today's Railways. March 2013. Issue 135. Page 31. The article states that the additional 8 units were initially 377624-634 but have been reclassified due to the dual-voltage option being taken up.
  12. ^ a b "Thameslink, Southern and Great Northern Franchise: Invitation to Tender" (PDF). London: Department for Transport. September 2013. p. 75. Retrieved 9 October 2013. 
  13. ^ "Trio of GTR Class 387/1s readied for move to Great Northern duties". PressReader. Retrieved 4 August 2016. 
  14. ^ Further boost for passengers as South West Trains secures additional carriages - South West Trains. 8 May 2012. Retrieved 21 January 2013.
  15. ^ "Procurement of New Rolling Stock" (Press release). Southern. 15 November 2012. 
  16. ^ "The Speed Run 2005". Flickr. Retrieved 10 October 2014.