The Class 171 Turbostar is a type of diesel multiple unit (DMU) train built by Bombardier Transportation (previously ADtranz) at its Litchurch Lane Works in Derby, England, which is identical to the Class 170, except for the replacement of the BSI (Bergische Stahl Industrie) coupler with a Dellner coupling. This provision was made to allow emergency joining with Class 377 DC third-rail electric units.