British Rail Class 172

British Rail Class 172 Turbostar
London Overground unit 172005 approaches Leytonstone High Road on the Gospel Oak to Barking Line
The interior of London Overground unit 172005.
In service	10 July 2010 - Present
Manufacturer	Bombardier Transportation
Family name	Turbostar
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
Operators	London Overground Chiltern Railways London Midland
Lines served	Snow Hill Lines Chiltern Main Line Chase Line Gospel Oak to Barking Line
Specifications
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)
Prime mover(s)	One per car, MTU 6H1800R83
Power output	485 hp (362 kW)
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+1⁄2 in) standard gauge

The Class 172 is a British diesel multiple-unit (DMU) train type of the Turbostar family, similar to the Class 168, Class 170 and Class 171. It was built by Bombardier Transportation at its Derby Works.

Technical details and variants

There will be four sub-types:

• Class 172/0 - two-car units in operation with London Overground
• Class 172/1 - two-car units to be operated by Chiltern Railways
• Class 172/2 - two-car units in operation with London Midland
• Class 172/3 - three-car units in operation with London Midland

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 London Midland resemble the Class 375, Class 377 and Class 379 Electrostars by having end gangways to allow access between units. These trains have a maximum speed of 100 mph (160 km/h).

Differences from other Turbostars

The Class 172 trains are lighter than other Turbostars thanks to the addition of lightweight bogies similar to those on the Class 220 Voyager trains. 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 correct lightweight bogies.

Differences from Class 150

Class 172s have fewer seats than the Class 150s they replace, 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.

Operators

London Overground

London Overground operates eight two-car Class 172s on the Gospel Oak to Barking Line, replacing the old Class 150 stock. The units were originally meant to be in service from February 2010, but due to production issues and then what were thought to be exhaust problems (which proved to be a false alarm), 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 Ltd (LOROL), the London Overground concession operator, from a rolling stock leasing company rather than them being purchased directly by Transport for London.

London Midland

London Midland will operate a total of 27 two-car and three-car units, originally planning for them to enter service by the end of 2010 on services to and from Birmingham Snow Hill, again replacing Class 150s. The London Midland sets have revised front ends with end gangways which make the trains look like the Electrostar Classes 375, 377 and 379.

From 1 September 2011, the first two diagrams began to be operated by the new Class 172 units. The 172s are now all in service and working all Snow Hill line services. They also make some weekend workings from New Street to Hereford. The 172s did have some issues in the first few months, however they've settled down providing a good service, with vibration at first having been sorted.

Chiltern Railways

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. 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 be 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.

• 
  London Overground unit 172004 stabled at Gospel Oak
• 
  London Midland unit 172213 passes Tamworth High Level en route from Derby Litchurch Lane
• 
  Chiltern Railways unit 172101 stands at London Marylebone

Introduction into service

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. 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.

Eight 172/0 units have been built for London Overground. Testing of the first batch of new units, the 172/0 sets for London Overground, commenced in March 2010, with two sets (anonymous as they did not have unit numbers on them) being tested on the Old Dalby Test Track. 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), 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. 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.

The four Chiltern Railways units entered service during summer 2011.

Fleet details

Class	Operator	Number built	Year built	Cars per set	Unit nos.
Class 172/0	London Overground South West Trains Southern Heathrow Connect Heathrow Express Greater Anglia Northern Rail First Great Western First TransPennine Express Arriva Trains Wales Gatwick Express First Capital Connect	8	2010	2	172001-172008
Class 172/1	Chiltern Railways	4	2011		172101-172104
Class 172/2	London Midland	12	2011		172211-172222
Class 172/3		15		3	172331-172345

Further potential orders

As part of its franchise agreement, London Midland has an option to purchase an additional 26 Class 172 vehicles which could potentially allow further cascade of its existing rolling stock.

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.

The Government announced in December 2008 that Bombardier, with its Turbostar design, was one of the pre-qualified bidders (along with CSR of China, CAF of Spain and Rotem of South Korea) for the first 200 DMU vehicles of its planned 1300 new carriages. These new trains were intended for use on suburban and inter-urban 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.

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.