In railway terminology, a single is a steam locomotive with a single pair of driving wheels. Some sources use 'Single' only for the 2-2-2 type, also known as a Jenny Lind locomotive, but more commonly singles could have any number of leading or trailing wheels. Rail terminology is a form of technical terminology. ... Great Western Railway No. ... On a steam locomotive, a driving wheel is a powered wheel which is driven by the locomotives pistons (or turbine, in the case of a steam turbine locomotive). ... Under the Whyte notation for the classification of steam locomotives, a 2-2-2 locomotive has two leading wheels, two driving wheels and two trailing wheels. ... The Jenny Lind locomotive was a steam locomotive built in 1847 for the London and Brighton Railway by The Railway Foundry of Leeds, named after Jenny Lind who was a famous opera singer of the period. ... On a steam locomotive, a leading wheel or leading axle is an unpowered wheel or axle located in front of the driving wheels. ... The trailing wheels (boxed) on a 4-6-2 locomotive. ...