In rail transport
is a system of classifying the arrangement of
the wheel assemblies
of a locomotive
by type, position, and connections.
There are serveral notations used to describe wheel arrangements,
the use of which varies by country. Within a given country
different notations may be employed for different kinds of
locomotives, such as steam
, and diesel
States, the United Kingdom and Ireland, the
Whyte notation is generally used for
practice uses a slightly simplified form of the UIC notation
for diesels and electrics.
The United States uses the AAR
scheme for diesels and electrics.
In mainland Europe
, the UIC classification
scheme is generally
used, with some exceptions. In France, the
UIC classification is 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
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.