British Rail Class 377
A Southern Class 377/7 at Watford Junction in 2017
The interior of a Southern Class 377/6
In serviceMay 2003 – present
ManufacturerBombardier Transportation
Built atDerby Litchurch Lane Works
Family nameElectrostar
ReplacedClass 313
Number built211 units
(excluding 28 375/3 conversions)
SuccessorClass 700 (Thameslink)
  • 377/1/2/4/5: 4 cars per unit (DMOC-MOSL-PTOSL-DMOC)
  • 377/3: 3 cars per unit (DMOC-PTOSL-DMOS)
  • 377/6/7: 5 cars per unit (DMOC-MOSL-PTOSL-MOS(2)-DMOS)
Car length20.4 m (66 ft 11+18 in)
Width2.80 m (9 ft 2+14 in)
Height3.78 m (12 ft 4+78 in)
Maximum speed100 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)
Traction motors4–8 × 200 kW (270 hp)
Power output
  • 1,200 kW (1,600 hp) (377/1, /2, /4, /5)
  • 800 kW (1,100 hp) (377/3 only)
  • 1,400 kW (1,900 hp) (377/6 and /7)
Electric system(s)
Current collector(s)
Coupling systemDellner
Multiple workingWithin class, Class 378[2] and Class 379[2]
Track gauge1,435 mm (4 ft 8+12 in) standard gauge

The British Rail Class 377 Electrostar is a British dual-voltage electric multiple unit passenger train (EMU) built by Bombardier Transportation on its Electrostar platform at Derby Litchurch Lane Works from 2001 to 2014.


Southern Class 377/1 departing Warnham
Southern Class 377/2 at Milton Keynes Central
Southern Class 377/4 at Hassocks
Southeastern Class 377/5 at London Victoria
Southern Class 377/6 about to depart at London Victoria
Southern Class 377/7 at East Croydon

The trains 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 that was more than 40 years old and 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 trains they replaced led to major upgrades being required to the 750 V DC third-rail power supply used in the former Southern region.[3] 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 an open area for wheelchairs or prams, 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.[4] The configuration of a 5-car Class 377 unit is:

In the 4-car units the driving cars are composite. The first-class saloon is between the driving cab and the first set of passenger doors. 4-car units also do not contain the MOS coach.[citation needed]


The Class 377 use Dellner instead of Tightlock couplings originally used on the Class 375s.[5] Southern's 375s were all reclassified to Class 377/3s upon conversion. 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 later converted from Tightlock to Dellner couplers but were not reclassified. Its sub-class 375/8 and 375/9 units were fitted with Dellner couplers, as built.[6]

Traction current supply

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 (and on single-voltage sub-class 377/6), the shoe mechanism is air-operated so that when powered down, or working on AC overhead lines, the shoe is raised out of the way. This is used on trains from Hemel Hempstead to Clapham Junction, which use part of the West Coast Main Line between Hemel Hempstead 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.[7] Since March 2009, dual-voltage Class 377 units operated some Thameslink Bedford to Brighton, Rochester and Ashford services (see below). The Bedford to Brighton services are now run by Class 700s, while the Class 377/5s themselves are now operated by Southeastern.

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.[citation needed]

Additional units and the Thameslink Programme

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 x 4-car units) due to be transferred to First Capital Connect.[8] Eleven further dual-voltage units were then added to the order, making a total of 23. 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 operated mainly on Bedford to Brighton services but in the peaks formed part of First Capital Connect's and Southeastern's joint service to places such as Rochester and Ashford.

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 it 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.[9]

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.[10] The contract was awarded to Bombardier in December 2011.[11][12] 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.[13]

In December 2011, three Class 377/2 units were transferred from Southern to First Capital Connect to allow more 12-car services to operate.[14]

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 in peak-hour services on the Sutton and Mole Valley lines, Epsom Downs Branch, Tattenham Corner Line and the Caterham Line.[citation needed]

Southeastern received 25 Class 377 units (the 23 Class 377/5s and 2 Class 377/1s) in recent years[when?], as specified in Department for Transport documents, published in September 2013, relating to the new combined Thameslink, Southern and Great Northern Franchise.[15]


Porterbrook is funding the £55 million five-year Project Aurora programme to refurbish 214 Class 377 Electrostars operated on Southern services.[16] The work started in 2020 and is being done at Selhurst depot. 377 430 was the first unit to be completed in early 2021.[17] Changes include the installation of screens showing live GTR and London Underground service information, the provision of USB and power points, energy-saving LED lighting and a passenger-counting system which will enable GTR to analyse how busy individual services are.[18]

Current operations



In December 2016 Southeastern (Govia) received 8 units (377501-377508), transferred from Thameslink. In September 2017 these were joined by an additional 17 units (377509-523 & 377163/164)

Aborted proposals

Great Northern

In 2016, 19 of the 23 Class 377/5 units were planned to be transferred to Great Northern, for use on non-stop London-Cambridge services. However, the 29 former Thameslink Class 387/1s were transferred, instead.[19] The Class 377/5s were later transferred to Southeastern, as part of their requirement for additional capacity.

Fleet details

Class Operator No. built Year built Cars Unit nos. Notes
377/1 Southern 64 2002–03 4 377101-164 All 3rd rail routes. 377163 and 377164 transferred from Southeastern to Southern on the 15th May 2022, following the retirement of the Class 455s.[20]
377/2 15 2003–04 377201-215 Dual-voltage units.
These are used on Metro routes in South London and occasionally main line workings to the South Coast.
377/3 28 2001–02 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 partly replaced by Class 313s.
377/4 75 2004–05 4 377401-475 All 3rd rail routes. 377442 returned back to /4 status Mid July 2021 after spending years as a 377/3.
377/5 Southeastern 23 2008–09 377501-523 Dual-voltage units.
All units were transferred from Thameslink to Southeastern during 2016–17 to bolster their existing Class 375 fleet.
377/6 Southern 26 2012–13 5 377601-626[13] Used on London suburban routes, extending as far as Dorking and Horsham, as well as Tattenham Corner/Caterham services, splitting and attaching at Purley. Run to Brighton at weekends. Also used on the East/West Coastway during events such as the Eastbourne Airshow.
377/7 8 2014 377701-708[13] Dual-voltage units.

Used on the East Croydon – Watford Junction/Hemel Hempstead services, and metro duties shared with the 377/6s.[21] The 8 sets were built as 5 car units 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
Southeastern Class 377

Accidents and incidents

377 317, Tonbridge, 23 August 2020.

On 28 November 2016, a fire broke out in the MOSL car of a Southern Class 377 (unit 377442) at Eastbourne station, causing damage to the ceiling and interior. The cause was later identified to be faulty wiring within a hand dryer located in the toilet.[22]

On 17 February 2018, a 377 (unit 377454) hit a car on a level crossing at Barns Green near Horsham. The two occupants of the car died at the scene.[23]

On 8 May 2019, 377142 collided with the buffer stop at London Victoria station.[24]

On 23 August 2020, 377317 was derailed at the exit of the Tonbridge Jubilee Sidings.[25]


  1. ^ Sherratt, Philip, ed. (2023). "ROSCO Fleets". Modern Railways: Review 2023. Stamford: Key Publishing. pp. 18–19. ISBN 978-1-80282-569-5.
  2. ^ a b Pritchard, R. N. (2012). British railways locomotives & coaching stock 2012. Platform 5. pp. 292, 294. ISBN 978-1-902336-92-3. OCLC 795598388.
  3. ^ Ford, Roger (May 2003). "SR power upgrade agreements signed". Modern Railways. London. Archived from the original on 4 June 2011.
  4. ^ First Capital Connect: Class 377 Drivers' Guide p.91 "The pantograph" 2009.
  5. ^ "Dellner Couplers AB — Automatic and Semi-Permanent Couplers". Retrieved 10 October 2014.
  6. ^ "Southern Electric Fleet Review Summer 2004". Southern Electric Group. 21 April 2006. Archived from the original on 23 February 2013.
  7. ^ Jacobs, G. (ed) (2008). Railway Track Diagrams 5: Southern and TfL (3rd edition). Bradford-on-Avon: Quail. p. 1R.
  8. ^ "More trains arriving on busy rail routes". Department for Transport. 4 April 2007. Archived from the original on 5 July 2007.
  9. ^ 350s with Southern until November Today's Railways UK issue 95 November 2009 page 65
  10. ^ "Battle of awarding of Thameslink contract to Siemens continues unabated as Southern potentially throws a lifeline to Bombardier's Derby works". Railway Herald. No. 283. Scunthorpe. 19 September 2011. p. 3. ISSN 1751-8091. Archived from the original (PDF) on 9 May 2012. Retrieved 30 October 2022.
  11. ^ "Boost for Derby as Bombardier wins Southern order". Railnews. 28 December 2011. Retrieved 9 January 2012.
  12. ^ "DfT acts to ease Thameslink trains logjam". Railnews. 16 November 2012. Retrieved 16 November 2012.
  13. ^ a b c Today's Railways UK. Sheffield. 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.
  14. ^ First Capital Connect runs first 12 car Thameslink train Rail issue 686 29 December 2011 page 14
  15. ^ "Thameslink, Southern and Great Northern Franchise: Invitation to Tender" (PDF). London: Department for Transport. September 2013. p. 75. Retrieved 9 October 2013.
  16. ^ "GTR launches £55m Electrostar refurbishment". Railway Gazette International. 16 September 2020. Retrieved 10 February 2021.
  17. ^ "Southern's first refurbished Electrostar returns to service". Railway Gazette International. 9 February 2021. Retrieved 10 February 2021.
  18. ^ "GTR launches £55m Electrostar refurbishment". Railway Gazette International. 16 September 2020. Retrieved 10 February 2021.
  19. ^ "Trio of GTR Class 387/1s readied for move to Great Northern duties". PressReader. Retrieved 4 August 2016.
  20. ^ "Units numbers 377 163 and 377 164 transfer from Southeastern to Southern exact dates". web)): CS1 maint: url-status (link)
  21. ^ "Procurement of New Rolling Stock" (Press release). Southern. 15 November 2012. Archived from the original on 29 March 2013.
  22. ^ "Hand dryer caused Eastbourne train fire". Eastbourne Herald. 2 December 2016. Retrieved 20 September 2018.
  23. ^ "Barns Green: Boy and granddad die as train hits car". BBC News. 17 February 2018. Retrieved 20 September 2018.
  24. ^ Clifton, Katy (8 May 2019). "Victoria station crash: Southern Rail train 'hits buffers causing loud bang and smoke' in front of shocked commuters". Evening Standard. Retrieved 8 May 2019.
  25. ^ Network Rail [@NetworkRailSE] (24 August 2020). "Due to Sunday's low-speed derailment of an empty train in the depot near Tonbridge Station our engineers are continuing to work to re-rail the train and check the signalling and track systems in the area" (Tweet). Retrieved 24 August 2020 – via Twitter.