UIC classification of locomotive axle arrangements
The UIC classification of locomotive axle arrangements, sometimes known as the German classification or German system, describes the wheel arrangement of locomotives, multiple units and trams. It is used in much of the world, notable exceptions being the United Kingdom and North America.
The classification system is managed by the International Union of Railways.
Structure
The UIC uses the following structure:; Upper-case letters : Indicate driving axles, starting at A for a single axle. B thus indicates two and C indicates three consecutive pairs of driving wheels, etc.
; Lower-case "o" : Related to driving axles, indicates they are individually driven by separate traction motors.
; Numbers : Consecutive non-driving axles, starting with 1 for a single axle.
; Prime symbol " ′ " : The axles indicated by a single letter or number are mounted on a bogie.
; Parentheses : Groups letters and numbers describing the same bogie. For example, indicates a three-axle bogie with the outer two axles driven. When parentheses are used around a single letter or number, a prime is not needed to indicate a bogie. Articulated locomotives can be indicated by bracketing the front power unit — for example, the Union [Pacific Big Boy], 4-8-8-4 in Whyte notation, is D2′ in UIC notation.
; Plus sign "+" : The locomotive or multiple unit consists of permanently coupled but mechanically separate traction units.
Garratt locomotives are indicated by bracketing or placing plus signs between all individual units.
; Other suffixes:
The most common wheel arrangements in modern locomotives are Bo′Bo′ and Co′Co′.
Examples
The following examples are based on the UIC classification:;
; BB
; B′B′
; Bo′
; Bo′Bo′
; Bo′Bo′Bo′
; C
; C′C′
; Co′Co′
;
; D
; 1′D1′
; E
;Cn2Gt
; 2′D1′h3S
; 1′E1′h2Gt
; 1′Dn4vP
; D′Dh4vtG