British Rail Class 172

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British Rail Class 172 Turbostar
172339 at Birmingham Moor Street.jpg
172342 DMSO Internal.jpg
The interior of a West Midlands Trains Class 172
In service 10 July 2010 - Present
Manufacturer Bombardier Transportation
Family name Turbostar
Replaced Class 150
Constructed 2010 - 2011
Number built 39 trainsets
Formation 2 or 3 cars per trainset
Capacity 172/0: 120 seats
172/1: ? seats
172/2: 116 seats
172/3: 188 seats
Operator(s) London Overground
Chiltern Railways
West Midlands Trains
Line(s) served Snow Hill Lines
Chiltern Main Line
Gospel Oak to Barking Line
Car body construction Welded aluminium. Steel ends.
Car length 23.62 m (77 ft 6 in)
Width 2.69 m (8 ft 10 in)
Height 3.77 m (12 ft 4 in)
Maximum speed 100 mph (160 km/h)
Weight 41.6 tonnes (40.9 long tons; 45.9 short tons)[1]
Prime mover(s) One per car, MTU 6H1800R83
Power output 483 hp (360 kW)[2]
Transmission ZF Ecomat-Rail 6 speed
ZF Reversing final drive
Safety system(s) AWS, TPWS
ATP (172/1 only)
Track gauge 1,435 mm (4 ft 8 12 in) standard gauge

The Class 172 is a British diesel multiple-unit (DMU) built by Bombardier Transportation's Derby Litchurch Lane Works for use on inner-suburban passenger services in the cities of London and Birmingham for London Overground, Chiltern Railways and West Midlands Trains.

The Class 172 is of the Turbostar model, similar to the Class 168, Class 170 and Class 171.

Technical details and variants[edit]

There are four sub-classes:

The 172/0s and 172/1s resemble the existing Turbostar trains in not having end gangways. These trains have a maximum speed of 100 mph (160 km/h).

The Class 172/2s and 172/3s used by West Midlands Trains resemble the Class 375, Class 377, Class 379 and Class 387 Electrostars by having end gangways to allow access between units.[3] These trains have a maximum speed of 100 mph (160 km/h).[4]

The Class 172s feature BSI (Bergische Stahl Industrie - Autocoupler) couplers which allow them to work in multiple with Class 170 units and most other units with the same coupler.

Differences from other Turbostars[edit]

The Class 172 trains are lighter than other Turbostars due to use of the Bombardier FLEXX-ECO bogies - a development of the B5000 bogies used on the Class 220 Voyager DEMU trains, rather than the previous 'Series 3' bogies.[5] Another difference is that they have half-height airdams as opposed to the more standard full height airdams. They also differ from earlier Turbostars in having mechanical transmission rather than hydraulic - gear changes can be distinctly heard as the trains accelerate and decelerate.

Class 172 with lightweight bogies.

Differences from Class 150[edit]

Class 172s have fewer seats than the Class 150s they replace,[4] but greater overall capacity due to the increased room for standing passengers as well as wider aisles intended to speed boarding and alighting and reduce waiting time in stations. The trains are air-conditioned and have no opening windows, unlike the Class 150s.

The Class 172 is designed to a 23 m (75 ft 6 in) body length, as opposed to the 20 m (65 ft 7 in) length used on previous Class 150 Sprinter DMUs - increasing capacity.


London Overground[edit]

The interior of a London Overground Class 172/0

London Overground operates eight two-car Class 172s on the GOBLIN (Gospel Oak to Barking Line), replacing the old Class 150 stock. The units were originally meant to be in service from February 2010,[6] but due to production issues and then what were thought to be exhaust problems (which proved to be a false alarm),[7] the trains entered service only in July 2010; and then at reduced capacity due to staff training problems. By December 2010 the whole fleet was in service, allowing the Class 150s to be cascaded to First Great Western and other operators. The units are leased by London Overground Rail Operations (LOROL), the London Overground concession operator, from a rolling stock leasing company rather than them being purchased directly by Transport for London.[8]

The success of London Overground's operation of the Gospel Oak to Barking Line meant that the 2-car Class 172s eventually proved insufficient in terms of capacity. Initially, there were plans to replace them with 3 or 4 car units DMUs.[9] However, subsequent to this proposal, the government announced plans to electrify the GOBLIN, with the intention that TfL will procure a new fleet of 4-car EMUs (Class 710) for use on both this route and the inner suburban routes from Liverpool Street, which was taken over by London Overground from 2015.[10] Electrification was completed in February 2018 (later than the original target of June 2017) and as of June 2018 the Class 172 units are set to be replaced by Class 710 EMUs from November 2018.[11]

West Midlands Trains[edit]

West Midlands Trains operate a total of 27 two-car and three-car units, ordered by predecessor London Midland, originally planning for them to enter service by the end of 2010 on services to and from Birmingham Snow Hill, again replacing Class 150s.[12] The West Midlands Trains sets have revised front ends with end gangways which make the trains look like the Electrostar family of units.

From 1 September 2011, the units started operating on the Snow Hill Lines with some weekend work from Birmingham - Hereford. When first used in service, the units suffered a fault with engine vibration in the passenger cabin, which has since been rectified.

The units were originally meant to replace all of the Class 150s, however three were retained. They are scheduled to be replaced by Class 153s, the Class 150's will then go to Northern.[13]

Chiltern Railways[edit]

A pair of Chiltern Railways Class 172/1 No. 172104 and No. 172102 at London Marylebone
The interior of a Chiltern Railways Class 172/1

Chiltern Railways has obtained four two-car trains in the same order as that of London Overground to supplement the current Class 165 Networker Turbos on its routes from London Marylebone, originally due to be delivered from late 2010.[14] They do not have the tripcock safety system installed—unlike the rest of the Chiltern Railways fleet—as the design of the bogie being used (based on the B5005 found on Class 220 Voyager and Class 222 Meridian trains) means there is no place for the brackets to be mounted. Thus, they are not able to operate on the Aylesbury via Amersham line whilst the current signalling system is in place unless running in multiple with other units on both the front and rear ends, which are fitted with a tripcock.

Introduction into service[edit]

In late 2007 and early 2008, orders were placed with Bombardier by two rolling-stock leasing companies to purchase a number of Class 172 Turbostar trains. In December 2007, Porterbrook ordered 15 three-car and 12 two-car trains for London Midland for delivery in 2010. In January 2008, Angel Trains, on behalf of London Overground and Chiltern Railways, ordered 12 two-car trains for delivery, which would have been delivered during 2009.[15] But difficulties over deliveries by Bombardier's suppliers led to delays in filling the Class 377 and 378 Electrostar orders, with subsequent knock-on delays for building the Class 172 sets. Work began at the end of 2009 after the freeing-up of one of Bombardier's production lines following completion of the Class 377 order for First Capital Connect.[16]

Eight 172/0 units were built for London Overground. Testing of the first batch of new units, the 172/0 sets for London Overground, commenced in March 2010 on the Old Dalby Test Track.[17] All units have subsequently been delivered to Willesden Train Maintenance Depot (TMD).

All eight 172/0 units have entered service for London Overground. These were originally restricted to a top speed of 40 miles per hour (64 km/h) as opposed to their intended design speed of 100 mph (160 km/h),[18] as it was thought there was a fault with the exhaust system requiring modifications to the original design and the already procured units. It was expected that units for London Midland and Chiltern would be delayed by a further 6–12 months.[19] However, it transpired that the exhaust emission testing had been flawed and that there were no major problems with the units or the original design. Production therefore continued as planned with a slight delay.[7]

The four Chiltern Railways units entered service during summer 2011.

Fleet details[edit]

Class Operator Number Year built Cars per set Unit nos.
Class 172/0[20] London Overground 7 2010 2 172001, 172003–008[21]
West Midlands Trains 1 172002
Class 172/1[22] Chiltern Railways 4 2011 172101–104[21]
Class 172/2[23] West Midlands Trains 12 2011 172211–222[21]
Class 172/3[23] 15 3 172331–345[21]

Further potential orders[edit]

In 2008, First Great Western applied to the Department for Transport to re-equip its Cardiff to Portsmouth via Bristol services with 11 new four-car DMUs which would potentially allow the existing Class 158 Express Sprinter trains to be transferred to other services. According to the West of England Partnership, these were likely to be "similar to Class 170s", suggesting that they might be Class 172 Turbostars.[24]

The Government announced in December 2008 that Bombardier, with its Turbostar design, was one of the pre-qualified bidders for the first 200 DMU vehicles of its planned 1300 new carriages.[25] These new trains were intended for services operated by First Great Western, First TransPennine Express and Northern Rail. However, with the announcement of the electrification schemes in the North West and on the Great Western Main Line, the DMU order was cancelled, with the needs of the train operating companies planned to be met by transfers of existing stock. However this eventually turned out not to be the case, and new trains were ordered by Northern and First TransPennine Express, manufactured by CAF and Hitachi.

Bombardier offered the Class 172 Turbostar to NI Railways for its "New Trains Two" specification, eventually losing out to CAF and a variation of NIR's existing Class 3000.[26]


The 172s on the Gospel Oak to Barking Line are due to be replaced by Class 710 Aventra electric units in spring 2018 following the completion of electrification in February 2018.[27] The Class 172 units will then transfer to West Midlands Railway.[28]

Accidents and incidents[edit]

  • On 8 September 2015, 172 338 was evacuated at Warwick Parkway after a fire near the running gear of one of the units.[29]


  1. ^ "Porterbrook Class 172 DMU" (PDF). Archived from the original (PDF) on 10 December 2015. 
  2. ^ "Class 172/0 - London Overground". 
  3. ^ "London Midlands Class 172/3 DMU, 172331, 5Z72 Derby Litchurch Lane - Old Dalby". Published Railways Illustrated Issue March 2011. [permanent dead link]
  4. ^ a b "". 
  5. ^ Gospel Oak to Barking improvement details.
  6. ^ "New Plans". The Barking - Gospel Oak Line User Group. Archived from the original on 21 August 2007. 
  7. ^ a b Ford, Roger (December 2010). "Bombardier recovering from multiple-unit hiccups". Modern Railways. London. pp. 32–33. 
  8. ^ "The Underground Roundel moves Overground". Today's Railways (UK). Sheffield (70): 24–30. September 2007. 
  9. ^ Government Online - New 3 or 4 car DMUs for London Overground Retrieved 9 August 2013
  10. ^ Ford, Roger (January 2014). "CP5 rolling stock market uncertain". Modern Railways. Key Publishing. 71 (784): 24–26. 
  11. ^ "New Overground Trains... Now With Wifi". Londonist. 
  12. ^ "Bombardier to supply 69 Turbostar cars to Porterbrook Leasing in 129 million euro contract for the UK" (Press release). Porterbrook. 13 December 2007. Archived from the original on 18 May 2011. Retrieved 5 July 2008. 
  13. ^ "London Midland launches £93m train fleet for Snow Hill line" (Press release). London Midland. 2 September 2011. Archived from the original on 24 September 2011. 
  14. ^ "Angel Trains orders 'green trains' for the UK rail market" (Press release). Angel Trains. 31 January 2008. 
  15. ^ "Class 172s ordered". Today's Railways (UK) (74). Sheffield. January 2008. pp. 56–58. 
  16. ^ 377/5 delays and its impact - London's Transport
  17. ^ Photos of the class 172s under test Archived 13 September 2009 at the Wayback Machine..
  18. ^ Miles, Tony (August 2010). "Class 172 ready for introduction". Modern Railways (743). London. p. 75. 
  19. ^ Modern Railways (741). July 2010.  Missing or empty |title= (help)
  20. ^ "Transport for London signs new train leasing contract" (Press release). Transport for London. 20 February 2008. 
  21. ^ a b c d Clinnick, Richard (2009). "Britain's future-facing fleets". Rail (634). Peterborough. pp. 66–73. 
  22. ^ "East-West Rail Scheme, United Kingdom". Railway Technology. 2011. Retrieved 24 April 2012. 
  23. ^ a b "Twenty seven new trains for London Midland" (Press release). London Midland. 13 December 2007. Archived from the original on 27 November 2010. 
  24. ^ Cardiff to Portsmouth New Trains Bid - West of England Partnership Archived 9 February 2009 at the Wayback Machine.
  25. ^ "Invitation to tender issued for 200 new diesel train carriages" (Press release). Department for Transport. 22 December 2008. [dead link]
  26. ^ Flanagan, Colm (2010). "Optimism in Northern Ireland". Modern Railways. 67 (737). pp. 60–64. 
  27. ^ "TfL tries to reduce line-closure time for GOBLIN electrification". 2 February 2016. 
  28. ^ First D-Trains lined up for West Midlands Trains in 2018 Rail (UK) 20 December 2017
  29. ^ Linning, Stephanie. "Terrifying moment smoke billows from train after fire broke out forcing 150 commuters to be evacuated". Mail Online. Associated Newspapers Ltd. Retrieved 21 April 2017.