- Wheel arrangement
Locomotive wheel arrangement is how the wheels of the locomotive are arranged by type, position, and connections. There are several notations used to describe wheel arrangements, depending on the country; also, a same country will typically use a different scheme for
steam locomotives on the one hand, and electric and diesel locomotives on the other hand.
United States, the United Kingdomand Ireland, the Whyte notationis generally used for steam locomotives. British practice uses a slightly simplified form of the UIC notation for diesels and electrics. The United States uses the AAR wheel arrangementscheme for diesels and electrics.
Europe, the UIC classificationscheme is generally used, with some exceptions. In France, the UIC classificationis used for diesels and electrics while a scheme similar to the Whyte notation, but counting axles insteads of wheels, is used for steam locomotives.
Especially in steam days, wheel arrangement was an important attribute of a locomotive, because there were many different ones, each optimised for a different use. Modern diesel and electric locomotives are much more uniform, usually with all axles driven.
Major Notation Schemes
AAR wheel arrangement- Used largely throughout the US and Canada.
UIC classification- Used for diesel and electric locomotives in the UK. Used in mainland Europe for all locomotive types, including steam.
Whyte notation- Used for shunting locomotives and steam locomotives in the UK.
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