Wheel arrangement

Locomotives of different types (Whyte and UIC wheel notation)

In rail transport, a wheel arrangement or wheel configuration is a system of classifying the way in which wheels are distributed under a locomotive.<ref>Template:Cite web</ref> Several notations exist to describe the wheel assemblies of a locomotive by type, position, and connections, with the adopted notations varying by country. Within a given country, different notations may also be employed for different kinds of locomotives, such as steam, electric, and diesel powered.

Especially in steam days, wheel arrangement was an important attribute of a locomotive because there were many different types of layout adopted, each wheel being optimised for a different use (often with only some being actually "driven"). Modern diesel and electric locomotives are much more uniform, usually with all axles driven.

Major notation schemes

Template:Commons category Template:Worldwide The main notations are the Whyte notation (based on counting the wheels), the AAR wheel arrangement notation (based on counting either the axles or the bogies), and the UIC classification of locomotive axle arrangements (based on counting either the axles or the bogies).

The Whyte notation is generally used for steam locomotives throughout the United States, Canada, the United Kingdom and Ireland. For diesels and electrics, North America uses the AAR wheel arrangement scheme while British practice uses a slightly simplified form of the European UIC classification scheme (except for small diesel shunters, where Whyte notation is used).

In mainland Europe, the UIC classification scheme is generally used for all locomotive types including steam, 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 instead of wheels, is used for steam locomotives. Notably, Switzerland had its own separate notation system until 1989, with the Swiss locomotive and railcar classification now only retained for its narrow-gauge railways.

• AAR wheel arrangement - Used largely throughout the US and Canada for diesel and electric locomotives.
• UIC classification - Used in mainland Europe for all locomotive types. Used in the UK for electric and large diesel locomotives.
• Whyte notation - Used in North America, the UK and Ireland for steam locomotives, and for shunter locomotives (US: switcher locomotives) in the UK.

Comparison of wheel arrangements and wheel picture

VDEV/VMEV/UIC-system	Whyte-notation	American name	Picture scheme Locomotive front is to the left
A1	0-2-2	Northumbrian
A2	0-2-4
1A	2-2-0	Planet
1A1	2-2-2	Single, Jenny Lind, Patentee
1A2	2-2-4	Aerolite
2Template:PrimeA	4-2-0	Jervis
2Template:PrimeA1	4-2-2
2A2	4-2-4	Huntington	File:WheelArrangement 4-2-4.svg
3A	6-2-0	Crampton	File:WheelArrangement 6-2-0.svg
N/A	0-3-0		File:WheelArrangement 0-6-0.svg
B	0-4-0	Four-Wheel-Switcher	File:WheelArrangement 0-4-0.svg
B1	0-4-2	Olomana	File:WheelArrangement 0-4-2.svg
B2Template:Prime	0-4-4	Forney four-coupled	File:WheelArrangement 0-4-4.svg
B3Template:Prime	0-4-6
1B	2-4-0	Porter	File:WheelArrangement 2-4-0.svg
1Template:PrimeB1Template:Prime	2-4-2	Columbia	File:WheelArrangement 2-4-2.svg
1B2Template:Prime	2-4-4	Forney, Mason Bogie	File:WheelArrangement 2-4-4.svg
1B3Template:Prime	2-4-6
2Template:PrimeB	4-4-0	American, Eight-Wheeler	File:WheelArrangement 4-4-0.svg
2Template:PrimeB1Template:Prime	4-4-2	Atlantic	File:WheelArrangement 4-4-2.svg
2Template:PrimeB2Template:Prime	4-4-4	Jubilee (CA), Reading (US)	File:WheelArrangement 4-4-4.svg
2Template:PrimeB3Template:Prime	4-4-6
C	0-6-0	Six-Wheel-Switcher	File:WheelArrangement 0-6-0.svg
C1	0-6-2	Webb, Branchline	File:WheelArrangement 0-6-2.svg
C2Template:Prime	0-6-4		File:WheelArrangement 0-6-4.svg
1Template:PrimeC	2-6-0	Mogul	File:WheelArrangement 2-6-0.svg
[[1Template:PrimeC1Template:Prime]]	2-6-2	Prairie	File:WheelArrangement 2-6-2.svg
1Template:PrimeC2Template:Prime	2-6-4	Adriatic, Lionel	File:WheelArrangement 2-6-4.svg
1Template:PrimeC3Template:Prime	2-6-6		File:WheelArrangement 2-6-6.svg
2Template:PrimeC	4-6-0	Ten-Wheeler	File:WheelArrangement 4-6-0.svg
2Template:PrimeC1Template:Prime	4-6-2	Pacific	File:WheelArrangement 4-6-2.svg
2Template:PrimeC2Template:Prime	4-6-4	Hudson (NYC), Baltic (MR), Shore Line (NH)	File:WheelArrangement 4-6-4.svg
D	0-8-0	Eight-Wheel-Switcher	File:WheelArrangement 0-8-0.svg
D1	0-8-2	Transfer	File:WheelArrangement 0-8-2.svg
D2Template:Prime	0-8-4		File:WheelArrangement 0-8-4.svg
D3Template:Prime	0-8-6
1Template:PrimeD	2-8-0	Consolidation	File:WheelArrangement 2-8-0.svg
1Template:PrimeD1Template:Prime	2-8-2	Mikado, MacArthur (USATC)	File:WheelArrangement 2-8-2.svg
1Template:PrimeD2Template:Prime	2-8-4	Berkshire, Kanawha (C&O), Lima (B&M)&(IC)	File:WheelArrangement 2-8-4.svg
1Template:PrimeD3Template:Prime	2-8-6		File:WheelArrangement 2-8-6.svg
2Template:PrimeD	4-8-0	Twelve-Wheeler, Mastodon	File:WheelArrangement 4-8-0.svg
2Template:PrimeD1Template:Prime	4-8-2	Mountain, Mohawk (NYC), New Haven (NH)	File:WheelArrangement 4-8-2.svg
2Template:PrimeD2Template:Prime	4-8-4	Northern, General Service (SP), Golden State (SP), Niagara (NYC), Wyoming (LV), Potomac (WM), Confederation (CN), Dixie (NC&St.L), Greenbrier (C&O), Laurentian (D&H), Montana (GN), Pocono (Lackawanna),	File:WheelArrangement 4-8-4.svg
2D3	4-8-6		File:WheelArrangement 4-8-6.svg
3Template:PrimeD3Template:Prime	6-8-6	Turbine (Pennsylvania Railroad Steam Turbine)	File:WheelArrangement 6-8-6.svg
E	0-10-0	Ten-Wheel Switcher	File:WheelArrangement 0-10-0.svg
E1Template:Prime	0-10-2	Union	File:WheelArrangement 0-10-2.svg
1Template:PrimeE	2-10-0	Decapod	File:WheelArrangement 2-10-0.svg
2Template:PrimeE	4-10-0	Mastodon, El Gobernador,	File:WheelArrangement 4-10-0.svg
1Template:PrimeE1Template:Prime	2-10-2	Santa Fe, Decapod (SP), Central (IC)	File:WheelArrangement 2-10-2.svg
1Template:PrimeE2Template:Prime	2-10-4	Texas, Selkirk (CP), Colorado (CB&Q)	File:WheelArrangement 2-10-4.svg
2Template:PrimeE1Template:Prime	4-10-2	Southern Pacific, Overland (UP)	File:WheelArrangement 4-10-2.svg
F	0-12-0	Pennsylvania, Twelve-Wheel-Switcher	File:WheelArrangement 0-12-0.svg
1Template:PrimeF	2-12-0	Centipede	File:WheelArrangement 2-12-0.svg
1Template:PrimeF1Template:Prime	2-12-2	Javanic	File:WheelArrangement 2-12-2.svg
2Template:PrimeF1Template:Prime	4-12-2	Union Pacific	File:WheelArrangement 4-12-2.svg
2Template:PrimeG2Template:Prime	4-14-4	Soviet (AA)	File:WheelArrangement 4-14-4.svg
ATemplate:PrimeA	0-2-2-0
BTemplate:PrimeB	0-4-4-0	nameless (Mallet)
BTemplate:PrimeB1	0-4-4-2	nameless (Mallet)
2Template:PrimeBB2Template:Prime	4-4-4-4	nameless (Pennsylvania Railroad Duplex)	File:WheelArrangement 4-4-4-4.svg
3Template:PrimeBB3Template:Prime	6-4-4-6		File:WheelArrangement 6-4-4-6.svg
2Template:PrimeCB2Template:Prime	4-6-4-4	nameless (Pennsylvania Railroad Duplex)	File:WheelArrangement 4-6-4-4.svg
CTemplate:PrimeC	0-6-6-0	Old Maude (Mallet)	File:WheelArrangement 0-6-6-0.svg
(1Template:PrimeC)C	2-6-6-0	nameless (Mallet)	File:WheelArrangement 2-6-6-0.svg
(1Template:PrimeC)C1Template:Prime	2-6-6-2	nameless (Mallet)	File:WheelArrangement 2-6-6-2.svg
(1Template:PrimeC)C2Template:Prime	2-6-6-4	nameless (Simple articulated)	File:WheelArrangement 2-6-6-4.svg
(2Template:PrimeC)C2Template:Prime	4-6-6-4	Challenger (Simple articulated)	File:WheelArrangement 4-6-6-4.svg
(1Template:PrimeC)C3Template:Prime	2-6-6-6	Allegheny, Blue Ridge (Simple articulated)	File:WheelArrangement 2-6-6-6.svg
DTemplate:PrimeD	0-8-8-0	Angus (Mallet)	File:WheelArrangement 0-8-8-0.svg
(1Template:PrimeD)D	2-8-8-0	Bull Moose (Mallet)	File:WheelArrangement 2-8-8-0.svg
(1Template:PrimeD)D1Template:Prime	2-8-8-2	Chesapeake (C&O), Cab Forward (SP) (Mallet)	File:WheelArrangement 2-8-8-2.svg
(1Template:PrimeD)D2Template:Prime	2-8-8-4	Yellowstone (Simple articulated)	File:WheelArrangement 2-8-8-4.svg
(2Template:PrimeD)D1Template:Prime	4-8-8-2	Cab Forward (Simple articulated)	File:WheelArrangement 4-8-8-2.svg
(2Template:PrimeD)D2Template:Prime	4-8-8-4	Big Boy (Simple articulated)	File:WheelArrangement 4-8-8-4.svg
(1Template:PrimeE)E1Template:Prime	2-10-10-2	Virginian (Mallet)	File:WheelArrangement 2-10-10-2.svg
(1Template:PrimeD1Template:Prime)(1Template:PrimeD1Template:Prime)	2-8-2+2-8-2	Nameless, Garratt	File:WheelArrangement 2-8-2+2-8-2.svg
(2Template:PrimeC1Template:Prime)(1Template:PrimeC2Template:Prime)	4-6-2+2-6-4	nameless (Garratt)	File:WheelArrangement 4-6-2+2-6-4.svg
(2Template:PrimeC2Template:Prime)(2Template:PrimeC2Template:Prime)	4-6-4+4-6-4	nameless (Garratt)	File:WheelArrangement 4-6-4+4-6-4.svg
(2Template:PrimeD)(D2Template:Prime)	4-8-0+0-8-4	nameless (Garratt)
(2Template:PrimeD1Template:Prime)(1Template:PrimeD2Template:Prime)	4-8-2+2-8-4	Double Mountain (Garratt)	File:WheelArrangement 4-8-2+2-8-4.svg
(2Template:PrimeD2Template:Prime)(2Template:PrimeD2Template:Prime)	4-8-4+4-8-4	nameless (Garratt)	File:WheelArrangement 4-8-4+4-8-4.svg

Geared steam locomotives

Geared steam locomotives such as Shays, Heislers, and Climaxes do not have a standard wheel arrangement classification system. Instead of being classified by wheel arrangement, they are instead classified by their design and their number of trucks.

No. of trucks	American name	Picture scheme
2-truck	Class A Shay, Class B Shay, Class A Climax, Class B Climax, Heisler	oo oo
3-truck	Class C Shay, Class C Climax, Heisler	oo oo oo
4-truck	Class D Shay	oo oo oo oo

See also

• Bo-Bo
• Bo-Bo-Bo
• Co-Co locomotives