British Rail Class 172

Bombardier Transportation

Industry	Rail vehicle manufacturing
Headquarters	Derby , United Kingdom
Products	Diesel multiple units (e.g. Class 172 Turbostar)

The British Rail Class 172 represents a diesel multiple unit (DMU) belonging to the Turbostar series, produced by Bombardier Transportation at the Derby Litchurch Lane Works facility. These units serve inner-suburban passenger routes and are exclusively operated by West Midlands Railway.

As part of the Bombardier Turbostar family, the Class 172 shares its design heritage with the Class 168, Class 170, and Class 171 models.

Technical specifications and variations

The fleet includes four distinct sub-classes, with West Midlands Railway deploying them across the Snow Hill Lines and the Leamington Spa to Nuneaton corridor:

• Class 172/0 – two-car formations without gangways; initially operated by London Overground
• Class 172/1 – two-car formations without gangways; originally assigned to Chiltern Railways
• Class 172/2 – two-car formations featuring gangways
• Class 172/3 – three-car formations equipped with gangways

The 172/0 and 172/1 variants resemble Turbostar trains lacking end gangways and have a top speed of .

In contrast, the Class 172/2 and 172/3 units used by West Midlands Trains include end gangways for inter-unit movement, similar in appearance to the , , , and Electrostar families. Their front-end styling is distinctive, adopting a Capitalstar-inspired design rather than the conventional Electrostar nose. These units also achieve maximum speeds of .

Initially, the 172/0s were constructed without onboard toilet facilities, aligning with London Overground standards; however, toilets were subsequently installed following their transfer to West Midlands Trains.

Class 172 units employ BSI (Bergische Stahl Industrie - Autocoupler) couplers, allowing compatibility for multiple working with , , and most other trains equipped with identical coupling systems.

Distinguishing features from other Turbostars

The Class 172 series is lighter in weight due to the integration of Bombardier FLEXX-ECO bogies, an advancement over the B5000 bogies found on Class 220 Voyager DEMUs, replacing the earlier ‘Series 3’ bogies. These trains utilize half-height airdams instead of full-height versions and incorporate mechanical transmission rather than hydraulic systems, resulting in noticeable gear shifts during acceleration and deceleration phases.

Differences compared to Class 150

When contrasted with the older units they replaced, the Class 172 trains offer fewer seats but increase total capacity by providing more standing space and wider aisles designed to facilitate quicker boarding and minimize station dwell times. Unlike Class 150s, these units feature air conditioning with sealed windows that do not open.

The overall body length of the Class 172 measures , surpassing the previous Class 150 Sprinter DMUs’ length of , thereby enhancing passenger accommodation.

West Midlands Railway

West Midlands Trains currently operates a fleet of 39 two- and three-car sets, including 27 ordered by its predecessor London Midland to supplant Class 150s on routes serving Birmingham Snow Hill. These units, featuring redesigned fronts and end gangways reminiscent of the Electrostar range, entered service on the Snow Hill Lines beginning in September 2011, covering some weekend services extending from Birmingham to Hereford. Early concerns about engine vibrations affecting passenger comfort were addressed successfully. Although intended to fully replace all Class 150s, three units were retained. From late 2018 into early 2019, London Overground’s fleet of 172/0s was transferred to West Midlands Railway to substitute remaining Class 150s and Class 153s on the Coventry–Leamington line and Coventry to Nuneaton line, while also boosting capacity on the Snow Hill Lines.

London Overground

The London Overground fleet included eight two-car Class 172 units deployed on the Gospel Oak to Barking line, replacing the older Class 150 trains. Although initially planned for introduction in February 2010, their entry into service was postponed until July 2010 due to manufacturing and training delays. By December of that year, all units were fully operational, allowing the displaced Class 150s to be reassigned to other operators. These trains were leased from Angel Trains.

Rising passenger numbers quickly made the two-car formations inadequate. Early proposals for longer diesel multiple units were superseded by a government-supported electrification initiative, with Transport for London acquiring new four-car electric multiple units (Class 710) to serve this line and additional inner-suburban routes transferred from Liverpool Street in 2015. The electrification project, originally targeted for mid-2017 completion, was finalized in February 2018.

Although Class 172s were slated to be replaced by Class 710 EMUs starting November 2018, they were temporarily substituted with Class 378 units reallocated within London Overground. The Class 172 vehicles were handed over to West Midlands Trains in March 2019 as Class 710s began entering service by May that year.

Chiltern Railways

Chiltern Railways took delivery of four two-car Class 172 trains to augment its existing Class 168 fleet operating from London Marylebone, with an anticipated arrival in late 2010. These units did not feature the tripcock safety apparatus found on other fleet members due to constraints related to their bogie design. This limitation restricted their operation on the Aylesbury via Amersham line unless coupled with tripcock-equipped units at both ends of the train.

In 2021, Chiltern’s entire Class 172 fleet was leased to West Midlands Trains to consolidate with their existing Class 172s ahead of introducing the new Class 196 Civity trains. It was subsequently confirmed that these Class 172/1 units would not return to Chiltern following the deployment of the Class 196 fleet.

Introduction into service

During late 2007 and early 2008, Bombardier secured orders from leasing companies for Class 172 Turbostar trains: Porterbrook commissioned fifteen three-car and twelve two-car sets for London Midland, while Angel Trains ordered twelve two-car sets intended for London Overground and Chiltern Railways. Delivery schedules were impacted by supplier-related production issues at Bombardier’s facilities, delaying completion until late 2009.

Eight units of the 172/0 subclass were constructed for London Overground, with testing commencing in March 2010 on the Old Dalby Test Track. All units were delivered to Willesden Traction Maintenance Depot (TMD) and entered service under an initial speed restriction due to suspected exhaust system defects. Further investigations found no significant design flaws, allowing production to proceed with only minor setbacks.

Chiltern Railways introduced its four Class 172 units into service in summer 2011; these were later transferred to West Midlands Railway in spring 2021.

Further potential orders

In 2008, First Great Western explored replacing its Cardiff to Portsmouth via Bristol services with eleven new four-car DMUs, potentially releasing existing Class 158 Express Sprinter trains for redeployment elsewhere. The West of England Partnership indicated these new trains would probably resemble "Class 170s," implying a likely choice of Class 172 Turbostar models.

In December of that year, the Government announced Bombardier’s Turbostar design as a pre-qualified bidder for the initial batch of 200 DMU vehicles within a broader plan for acquiring up to 1300 new carriages. These trains were intended for deployment by First Great Western, First TransPennine Express, and Northern Rail. However, subsequent electrification projects on both the North West and Great Western Main Lines led to cancellation of this DMU order, with train operating companies expected to fulfill requirements through reallocations of existing rolling stock.

Later acquisitions saw Arriva Rail North and TransPennine Express (First Group) procure new DMU and bi-mode fleets from CAF and Hitachi in substantially larger numbers—Arriva Rail North alone received fifty-eight CAF DMUs—far exceeding the originally planned sixty-one Class 172 units intended across three operators.

Bombardier also proposed the Class 172 Turbostar for NI Railways’ "New Trains Two" initiative but ultimately lost out to CAF’s version based on the existing Class 3000 platform.

Fleet details

Class	Operator	Quantity	Year of manufacture	Cars per set	Unit numbers
172/0	West Midlands Railway	8	2010	2	172001–172008
172/1		4	2011		172101–172104
172/2		12			172211–172222
172/3		15		3	172331–172345

Vehicle weights

Class	DMOS vehicles weight	MOS vehicles weight	DMOSLW vehicles weight
172/0	41.85 t (41.19 long tons; 46.13 short tons)	—	42.40 t (41.73 long tons; 46.74 short tons)
172/1
172/2	41.87 t (41.21 long tons; 46.15 short tons)	—	42.49 t (41.82 long tons; 46.84 short tons)
172/3		38.75 t (38.14 long tons; 42.71 short tons)

Named unit

A single unit carries a dedicated name:

172342: Roger Sumner – commemorating a Worcester-based driver who retired in late 2022 after an almost six-decade career, and was the final West Midlands Trains staff member with steam locomotive experience dating back to British Rail.