British Rail Class 171

British Rail Class 171 Turbostar
Southern 171721 at Hastings in 2014
The Standard Class interior aboard a Class 171
In service	2003 - present
Manufacturer	Bombardier Transportation
Built at	Derby Litchurch Lane Works
Family name	Turbostar
Replaced	Class 205 Class 207
Constructed	2003–2004
Number built	20 sets
Number in service	17 sets
Formation	2 or 3 cars per unit[1]
Fleet numbers	171201 171727 – 171730 171801 – 171812
Capacity	107 seats (2 Car) 241 seats (former 4 Car)[2]
Operators	Southern
Specifications
Car length	23.62 m (77 ft 5+7⁄8 in)
Width	2.69 m (8 ft 9+7⁄8 in)
Height	3.77 m (12 ft 4+3⁄8 in)
Maximum speed	100 mph (160 km/h)
Weight	Class 171/7: 90.41 tonnes (88.98 long tons; 99.66 short tons) Class 171/8: 176.21 tonnes (173.43 long tons; 194.24 short tons)
Prime mover(s)	One MTU 6R 183TD13H per car
Engine type	Turbo-diesel
Cylinder count	6
Displacement	13 L (790 cu in)
Power output	422 hp (315 kW) per engine
Transmission	Voith Hydraulic T211rzze 2 axles driven per car
Acceleration	0.5 m/s2 (1.1 mph/s)[3]
Braking system(s)	Air[2]
Safety system(s)	AWS, TPWS
Coupling system	Dellner
Multiple working	Within class
Track gauge	1,435 mm (4 ft 8+1⁄2 in) standard gauge

The British Rail Class 171 Turbostar is a type of diesel-hydraulic multiple unit passenger train built by Bombardier Transportation at Derby Litchurch Lane Works in England. It is identical to the Class 170, except for the replacement of the BSI coupler with a Dellner coupler. This provision was made to allow emergency joining with Class 377 DC third-rail electric units, which Southern runs extensively on most lines. The units work on the southern regions of the British railway system, operating services from London Bridge to Uckfield and from Eastbourne to Ashford International, these routes being unelectrified between Hurst Green Junction and Uckfield and between Ore and Ashford International, respectively.

The fleet is operated by Govia Thameslink Railway on Southern services.