Class 172 Turbostar

The Class 172 is a member of the Turbostar family (such as the Classes 170 and 171). It is similar to the Class 170 but has diesel-mechanical transmission and a more austere interior to suit inner-suburban routes. They are also lighter due to a different bogie being used.

They were ordered for London Overground, Chiltern Railways and London Midland (now West Midlands Railway) [1] The London Overground sets are likely to be cascaded elsewhere once electrification of the Gospel Oak-Barking Line they operate on is completed. Chiltern 172s cannot be fitted with tripcocks (a safety system used by London Underground) unlike their other DMUs because of the bogies used which means they cannot operate on the Aylesbury via Amersham Line unless running with another so-equipped DMU.

Number built: 117 (39 2 or 3 car sets)
Built: 2010-11
Builder: Bombardier Derby
Engine: MTU 6H1800R83 diesel per vehicle
Power: 968hp (720kW) / 1, 449hp (1, 080kW)
Formation: Driving Motor Standard (DMS)+DMS or
DMS+Driving Motor Standard Lavatory (DMSL) or
DMSL+Motor Standard (MS)+DMS

It is in service with London Overground (Class 172/0), Chiltern Railways (Class 172/1) and West Midlands Railways (Class 172/2 and 172/3). The London Midland examples have end-gangways in the Electrostar style. The 172/3 are 3-car sets with the other sub-classes being 2-car.
Chiltern 172 104 at Princes Risborough

London Midland (as it was then) 172 331 at Worcester Shrub Hill

West Midlands Railway 172 339 at Birmingham Snow Hill 
LM 172 335 and 332 at Birmingham Moor Street

London Overground 172 008 at Gospel Oak

WMR 172 335 at Dorridge

[1] Colin J Marsden, DMU and EMU Recognition Guide (Ian Allan, 2013) p. 162