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The 'UIC classification' is a comprehensive system for describing the wheel arrangement of locomotives, multiple units and trams. It is the system generally used in much of the world, but it was not widely used in the United Kingdom, other than partially on the Southern Railway under chief engineer Oliver Bulleid, or in the United States; a simplified form (AAR wheel arrangement) is used in both countries for modern locomotives. It is a more versatile system than Whyte notation, making fewer assumptions about locomotive layout. In the latter notation, some locomotives are impossible to classify; UIC classification handles them easily. The UIC classification is also much more suited to diesel and electric locomotives.
Whereas the Whyte notation counts wheels, the UIC notation counts pairs of wheels (called "wheelsets" or informally "axles").
;Upper-case letters:Designate a number of consecutive driving axles, starting at A for a single axle. C thus indicates three consecutive pairs of driving wheels.
;Numbers: Designate consecutive non-driving axles, starting with 1 for a single axle.
;Lower-case "o":On many electric and diesel-electric locomotives, axles are individually driven by electric motors — this is indicated by suffixing the driving wheel letter with a lower-case "o".
;Prime sign " ' ": Indicates that the axles are mounted on a steerable bogie.
;Plus sign "+":Indicates that the locomotive or multiple unit consists of permanently coupled individual vehicles.
;Brackets: Can be used to group letters and numbers describing the same bogie. For example, (A1A) indicates a three axle bogie with the outer two axles driven. When brackets are used a prime is not needed to indicate a bogie.
Mallet locomotives can be indicated by bracketing the front power unit — for example, the Union Pacific Big Boy — denoted 4-8-8-4 in Whyte notation, is designated (2'D)D2' in UIC notation. Garratt-type locomotives are indicated by bracketing or placing plus signs between all individual units. Mechanically-separated permanently-coupled units are indicated using only a "+" (plus) sign.
;Other Suffixes:The designation can also have additional suffixes, denoting other features of the locomotive:
:
★ h: Superheated Steam (German: ''Heißdampf'')
:
★ n: Saturated Steam (German: ''Naßdampf'')
:
★ v: Compound (German: ''Verbund'')
:
★ Turb: Turbine
:
★ t: Tank locomotive
and sometimes followed by a number, indicating the number of cylinders in a steam locomotive.
The most common wheel arrangements in modern locomotives are Bo'Bo' or Co'Co', while steam locomotives and other older units can have many different wheel arrangements.

Contents

Examples

References

See also

Examples

;(A1A)(A1A):
"(A1A)(A1A) " means there are two bogies or wheel assemblies under the unit. Each bogie has one powered axle, one idle axle, and one more powered axle, an arrangement intended to provide better load distribution and thereby reduce the wheel load on the track. All powered axles are individually driven (i.e., via traction motors).
;BB:
"BB" means that there are four powered axles all mounted in the locomotive's frame. They are driven in pairs; i.e. each pair of axles is connected by driving rods or gears. Compare with "D" below.
;B'B':
"B'B' " means there are two bogies or wheel assemblies under the unit. Each truck has two powered axles, connected by driving rods or gears. Three-quarters of all modern locomotives (as well as the power cars of self-propelled trains) are configured in either this or the "Bo'-Bo'" arrangement.
;Bo'(A1A):
"Bo'(A1A) " means there are two trucks or wheel assemblies. The "Bo'" truck is under one end of the unit, and has two powered axles, while the "(A1A)" truck is under the other end of the unit, and has one powered axle, one idle axle, and one more powered axle. All powered axles are individually driven (i.e., via traction motors).
;Bo'Bo':
"Bo'Bo' " means there are two bogies or wheel assemblies under the unit. Each truck has two individually-driven powered axles (i.e., via traction motors). Three-quarters of all modern locomotives (as well as the power cars of self-propelled trains) are configured in either this or the "B'B'" arrangement. Many types of tram use this arrangement.
;C'C':
"C'C' " means there are two bogies or wheel assemblies under the unit. Each truck has three powered axles, connected by driving rods or gears.
;Co'Co':
"Co'Co' " means there are two bogies or wheel assemblies under the unit. Each truck has three individually-driven, powered axles (i.e., via traction motors).
;D:
"D" means that there are four powered axles, connected by driving rods or gears, all mounted in the locomotive's frame.
;1'D1':
"1'D1' " means that there is one leading idle (non-driven) axle mounted in a bogie, four driven axles mounted in the frame and connected by driving rods or gears, followed one trailing idle axle mounted in a bogie.

References

★ http://www.skyrocket.de/locomotive/data/achsfolge.htm

See also

★ AAR wheel arrangement

★ Wheel arrangement

★ Whyte notation

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