UIC axle classification

The UIC classification is a system for explaining the wheel arrangement of diesel locomotives, electric locomotives, and multiple-units.
The system was developed by the International Union of Railways; its acronym comes from the French: Union Internationale des Chemins de fer meaning the same. It was developed to be superior to the Whyte notation which cannot classify every arrangement type properly.
==Syntax==
The system has a lot more rules than the Whyte Notation:
*Capital letters denote consecutive powered axles. A = 1 powered axle; B = 2; C = 3 etc.
*The lower case letter 'o' denotes driving wheel: so a Bo truck(bogie) would have two separately powered axles.
*Numbers denote a consecutive non-powered axle. So 1 = one non-powered axle; 2 = two non-powered axles etc.
*Brackets and apostrophes indicate sets of axels that are mounted on an element that swivels relative to the main frame. An apostrophe ( ' ) applied to a single letter or number indicates that the corresponding axels are mounted on a bogie (possibly in turn mounted in turn on a truck). Brackets "()" indicates multiple letters and numbers representing axles on the same bogie or truck (some of which may be in turn on bogies). When used with single letters or numbers (instead of an apostrophe) they may indicate articulation rather than simple trucks.
*A plus sign (+) shows completely separate mechanical systems, as in Multiple Unit.
==Examples (Diesel)==
*Co'Co' = Six axles;
*Bo'Bo' = Four axles;
*Do'Do' = Eight axles;
*(A1A)(A1A) = Two trucks with unpowered axles between them
*Bo'Bo'+Bo'Bo' = As in semi-permanently coupled carriages in a Trainset.
*Bo'Co' = Two axles at the front, three in the rear
*Co'Bo' = Three axles in the front truck and two in the rear.
*(D)(D) = Shows that the body of the locomotive is articulated, as in a rail crane.
==Examples (Steam)==
This section shows what the differences are between the Whyte notation and the UIC classification. The latter is not used for steam locomotives though.
*The "Pacific" axle arrangement under the Whyte notation is 4-6-2. Under the UIC classification this would be: 2'C1'.
*The "Big Boy" articulated is 4-8-8-4 under the Whyte system. Under the UIC classification it is: (2'D)D2'.
==References==
*Book: The Railway Data File published by Silverdale Books. .
*Wikipedia.org
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