Whyte notation

The Whyte notation is a classification method for steam locomotives, and some internal combustion locomotives and electric locomotives, by wheel arrangement. It was devised by Frederick Methvan Whyte, and came into use in the early twentieth century following a December 1900 editorial in American Engineer and Railroad Journal.

A selection of early 20th century locomotive types according to their Whyte notation and their comparative size

Whyte notation from a handbook for railroad industry workers published in 1906

The notation was adopted and remains in use in North America and the United Kingdom to describe the wheel arrangements of steam locomotives, but for modern locomotives, multiple units and trams it has been supplanted by the UIC system in Europe and by the AAR system (essentially a simplification of the UIC system) in North America. However, geared steam locomotives do not use the notation. They are classified by their model and their number of trucks.

Structure of the system

Basic form

The notation in its basic form counts the number of leading wheels, then the number of driving wheels, and finally the number of trailing wheels, numbers being separated by dashes. For example, a locomotive with two leading axles (four wheels) in front, then three driving axles (six wheels) and then one trailing axle (two wheels) is classified as a 4-6-2 locomotive, and is commonly known as a Pacific.

Denotion of other locomotives

Articulated locomotives

For articulated locomotives that have two wheelsets, such as Garratts, which are effectively two locomotives joined by a common boiler, each wheelset is denoted separately, with a plus sign (+) between them. Thus a 4-6-2-type Garratt is a 4-6-2+2-6-4. For Garratt locomotives, the plus sign is used even when there are no intermediate unpowered wheels, e.g. the LMS Garratt 2-6-0+0-6-2. This is because the two engine units are more than just power bogies. They are complete engines, carrying fuel and water tanks. The plus sign represents the bridge (carrying the boiler) that links the two engines.

Simpler articulated types, such as Mallets, have a jointed frame under a common boiler where there are no unpowered wheels between the sets of powered wheels. Typically, the forward frame is free to swing, whereas the rear frame is rigid with the boiler. Thus, a Union Pacific Big Boy is a 4-8-8-4: four leading wheels, one group of eight driving wheels, another group of eight driving wheels, and then four trailing wheels. Sometimes articulated locomotives of this type are denoted with a “+” between each driving wheels set (so in the previous case, the Big Boy would be a 4-8+8-4). This may have been developed to distinguish articulated and duplex arrangements; duplex arrangements would get a “-“ being rigid and articulated locomotives would get a “+” being flexible. However, given all the wheel arrangements for duplex locomotives have been mutually exclusive to them, it is usually considered unnecessary and thus another “-“ is usually used.

Triplex locomotives, and any theoretical larger ones, simply expand on basic articulated locomotives, for example, 2-8-8-8-2. In the case of the Belgian quadruplex locomotive, the arrangement is listed as 0-6-2+2-4-2-4-2+2-6-0.

Duplex locomotives

For duplex locomotives, which have two sets of coupled driving wheels mounted rigidly on the same frame, the same method is used as for Mallet articulated locomotives – the number of leading wheels is placed first, followed by the leading set of driving wheels, followed by the trailing set of driving wheels, followed by the trailing wheels, each number being separated by a hyphen.

Tank locomotives

A number of standard suffixes can be used to extend the Whyte notation for tank locomotives:

Suffix	Meaning	Example
[No Suffix]	Tender locomotive	0-6-0
T	Tank locomotive	0-6-2T
ST	Saddle tank locomotive	0-4-0ST
WT	Well tank locomotive	0-4-0WT
PT	Pannier tank locomotive	0-6-0PT
C or CT	Crane tank locomotive	0-6-2CT
IST	Inverted saddle tank locomotive	0-4-2IST
T+T (or ST+T, WT+T, etc.)	Tender-tank locomotive	0-4-0T+T
WT	Wing tank locomotive	0-4-0WT
RT	Rear tank locomotive	0-4-4RT

Other steam locomotives

Various other types of steam locomotive can be also denoted through suffixes:

VB or VBT		Vertical boilered locomotive	0-6-0VB
F		Fireless locomotive	0-6-0F
CA		Compressed air locomotive	0-6-0CA
R		Railcar	0-4-4-0R
R or RT		Rack locomotive	0-4-0RT

Internal combustion locomotives

The wheel arrangement of small diesel and petrol locomotives can be classified using the same notation as steam locomotives, e.g. 0-4-0, 0-6-0, 0-8-0. Where the axles are coupled by chains or shafts (rather than side rods) or are individually driven, the terms 4w (4-wheeled), 6w (6-wheeled) or 8w (8-wheeled) are generally used. For larger locomotives, the UIC classification is more commonly used.

Various suffixes are also used to denote the different types of internal combustion locomotives:

Suffix	Meaning	Example
PM	Petrol-mechanical locomotive	4wPM
PE	Petrol-electric locomotive	0-6-0PE
D	Diesel locomotive	6wD
DM	Diesel–mechanical locomotive	8wDM
DE	Diesel–electric locomotive	0-4-0DE
DH	Diesel–hydraulic locomotive	0-6-0DH

Electric locomotives

The wheel arrangement of small electric locomotives can be denoted using this notation, like with internal combustion locomotives.

Suffixes used for electric locomotives include:

Suffix	Meaning	Example
BE	Battery-electric locomotive	4wBE
OE	Overhead-lines electric locomotive	0-8-0OE
RE	Third rail electric locomotive	4wRE

Wheel arrangement names

In American (and to a lesser extent British) practice, most wheel arrangements in common use were given names, sometimes from the name of the first such locomotive built. For example, the 2-2-0 type arrangement is named Planet, after the 1830 locomotive on which it was first used. (This naming convention is similar to the naming of warship classes.) Note that several wheel arrangements had multiple names, and some names were only used in some countries.

Wheel arrangements under the Whyte system are listed below. In the diagrams, the front of the locomotive is to the left.

Arrangement (locomotive front is to the left)	Whyte classification	Name	No. of units produced
Non-articulated locomotives
	0-2-2	Northumbrian (after the 1830 locomotive Northumbrian)
	0-2-4
	2-2-0	Planet
	2-2-2	Single, Jenny Lind
	2-2-4	Aerolite
	4-2-0	Jervis
	4-2-2	Bicycle
	4-2-4	Huntington
	6-2-0	Crampton
	0-4-0	Four-wheel switch
	0-4-0+4
	0-4-2	Olomana
	0-4-4	Forney
	2-4-0	Porter, 'Old English'
	2-4-2	Columbia
	2-4-4	Forney, Mason Bogie
	4-4-0	American, eight-wheeler
	4-4-2	Atlantic
	4-4-4	Reading, Jubilee (Canada)
	0-3-0	(one driving wheel per axle; used on Patiala State Monorail Trainways and also on the Listowel and Ballybunion Railway)
	0-6-0	Six-coupled, Six-wheel switch, Bourbonnais (France - tender), Boer (France - tank)
	0-6-2	Branchliner, Webb
	0-6-4	Forney six-coupled
	0-6-6	Forney six-coupled
	2-6-0	Mogul	11,000
	2-6-2	Prairie
	2-6-4	Adriatic
	2-6-6	Mason Bogie
	4-6-0	Ten-wheeler (not Britain)
	4-6-2	Pacific	6,800
	4-6-4	Hudson, Baltic
		Use on the Boston and Albany Railroad.
	0-8-0	Eight-coupled
	0-8-2	Transfer
	0-8-4
	2-8-0	Consolidation	35,000
	2-8-2	Mikado, Mike, MacArthur
	2-8-4	Berkshire, Kanawha
	2-8-6	Used only on four Mason Bogie locomotives
	4-8-0	Twelve Wheeler, Mastodon
	4-8-2	Mountain, Mohawk (NYC)
	4-8-4	Northern, Niagara, Confederation, Dixie, Greenbrier, Pocono, Potomac, Heavy Mountain (Atchison, Topeka, and Santa Fe), Golden State (Southern Pacific), Western, Laurentian (Delaware & Hudson Railroad), General, Wyoming (Lehigh Valley), Governor, Big Apple, GS Series "Daylight" (Southern Pacific)
	4-8-6	Proposed by Lima, never built
	6-8-6	Turbine, only used on the PRR S2 Steam Turbine	1
	0-10-0	Ten-coupled, Ten-wheel switch
	0-10-2	Union
	2-10-0	Decapod, Russian Decapod
	2-10-2	Santa Fe
	2-10-4	Texas, Colorado (CB&Q), Selkirk (Canada)
		Proposed by Indian Railways, never built
	4-10-0	Mastodon
	4-10-2	Reid Tenwheeler, Southern Pacific, Overland, Super Mountain
	0-12-0	12-coupled
	0-12-2	Used in Argentina
	2-12-0	Centipede
	2-12-2	Javanic	30
	2-12-4		20
		Proposed by Lima, never built
	4-12-2	Union Pacific
	4-14-4	AA20, Soviet	1
Divided drive and duplex locomotives
	0-2-2-0	Used on the Mount Washington Cog Railway
	2-2-2-0
	2-2-2-2
	2-2-4-0		1
	4-2-2-0	Double single
	2-4-6-2
	4-4-4-2	Planned for proposed ACE 3000 locomotive.
	4-4-4-4	(PRR T1)	53
	6-4-4-6	(PRR S1)	1
	4-4-6-4	(PRR Q2)	26
	4-6-4-4	(PRR Q1)	1
Articulated locomotives (simple and compound)
	0-4-4-0
	2-4-4-0		5
	0-4-4-2
	2-4-4-2	Little River
	4-4-6-2	Used by the Santa Fe	2
	0-6-6-0
	2-6-6-0
	2-6-6-2		1,300
	2-6-6-4		60
	2-6-6-6	Allegheny, Blue Ridge	68
	4-6-6-2	(Southern Pacific class AM-2)
	4-6-6-4	Challenger	252
	0-8-6-0
	2-6-8-0	(Southern Railway, Great Northern Railway)	39
	0-8-8-0	Angus
	2-8-8-0	Bull Moose
	2-8-8-2	Chesapeake	222
	2-8-8-4	Yellowstone	78
	4-8-8-2	Cab Forward	195
	4-8-8-4	Big Boy	25
	2-10-10-2	(Santa Fe and Virginian railroads)	20
	2-8-8-8-2	Triplex (Erie RR)	3
	2-8-8-8-4	Triplex (Virginian RR)	1
Garratt articulated locomotives
	0-4-0+0-4-0
	0-6-0+0-6-0
	2-4-0+0-4-2
	2-4-2+2-4-2
	2-6-0+0-6-2
	2-6-2+2-6-2	Double Prairie
	2-8-0+0-8-2
	2-8-2+2-8-2	Double Mikado
	4-4-2+2-4-4
	4-6-0+0-6-4
	4-6-2+2-6-4	Double Pacific
	4-6-4+4-6-4	Double Hudson
	4-8-0+0-8-4
	4-8-2+2-8-4
	4-8-4+4-8-4

See also

• AAR wheel arrangement
• Swiss locomotive and railcar classification
• UIC classification
• Wheel arrangement

References

1. Colvin, Fred H. (1906). The railroad pocket-book: a quick reference cyclopedia of railroad information. New York, Derry-Collard; London, Locomotive Publishing Company (US-UK co-edition). p. L‑9.
2. "Steam Locomotive Glossary". Railway Technical Web Pages. 28 June 2007. Archived from the original on 28 January 2008. Retrieved 8 February 2008.
3. Thompson, Keith (1 May 2006). "Builder's plates: A locomotive's birth certificate". Kalmbach Publishing. Archived from the original on 22 November 2008. Retrieved 8 February 2008.
4. "The Franco-Crosti Boiler System".
5. Industrial Locomotives: including preserved and minor railway locomotives. Vol. 17EL. Melton Mowbray: Industrial Railway Society. 2015. ISBN 978 1 901556 88 9.
6. Directory of Railway Officials & Year Book 1956-1957. London: Tothill Press Limited. 1956. p. 421.
7. White, John H. Jr. (1968). A History of the American Locomotive - Its Development: 1830-1880. New York: Dover Publications. ISBN 0-486-23818-0., p. 33.
8. Adams, Bob (December 1968). "The Crampton Type Locomotive on the Camden & Amboy Railroad". NMRA Bulletin. National Model Railroad Association.
9. Ellis, C Hamilton, Some Classic Locomotives, Allen & Unwin, 1949.173 p.
10. White (1968), p. 46.
11. Marsden, Richard (2008). "The LNER 4-4-2 Atlantic Locomotives". The London & North Eastern Railway (LNER) Encyclopedia. Archived from the original on 13 February 2008. Retrieved 8 February 2008.
12. "Canadian Pacific Railway No. 2929". Steamtown NHS Special History Study. United States National Park Service. 14 February 2002. Archived from the original on 19 May 2007. Retrieved 8 February 2008.
13. White (1968), p 62-65.
14. White (1968), p. 57.
15. Marsden, Richard (2008). "LNER 4-6-0 Locomotives". The London & North Eastern Railway (LNER) Encyclopedia. Archived from the original on 13 February 2008. Retrieved 8 February 2008.
16. Marsden, Richard (2008). "LNER 4-6-2 Pacific Locomotives". The London & North Eastern Railway (LNER) Encyclopedia. Archived from the original on 25 February 2008. Retrieved 8 February 2008.
17. "Pacifics". SteamLocomotive.com. Archived from the original on 25 January 2008. Retrieved 8 February 2008.
18. "Hudsons". SteamLocomotive.com. Archived from the original on 27 January 2008. Retrieved 8 February 2008.
19. "Boston & Albany 4-6-6 Locomotives in the USA". steamlocomotive.com. Retrieved 21 April 2021.
20. White (1968), p. 65.
21. "Glossary of Common Railroad Terms: M". Kalmbach Publishing. Archived from the original on 24 February 2008. Retrieved 8 February 2008.
22. "The Mikado Type Locomotive". SteamLocomotive.com. Archived from the original on 12 June 2013. Retrieved 8 February 2008.
23. Farrell, Jack W. (1989). North American steam locomotives: The Berkshire and Texas types. Edmonds, WA. ISBN 0-915713-15-2. {{cite book}}: |work= ignored (help)CS1 maint: location missing publisher (link)
24. "Berkshires & Kanawhas". SteamLocomotive.com. Archived from the original on 26 January 2008. Retrieved 8 February 2008.
25. "Locomotives: Whyte's Notation". Locomotive Cyclopedia of American Practice. Simmons-Boardman Publishing Corporation. 1922. pp. 106–107.
26. "Mountains". SteamLocomotive.com. Archived from the original on 30 January 2008. Retrieved 8 February 2008.
27. Taylor, Frank (January 1941). "New York Central Dual-service Mohawk". Model Railroader. Kalmbach Publishing.
28. "Northerns". SteamLocomotive.com. Archived from the original on 12 February 2008. Retrieved 8 February 2008.
29. "Lehigh Valley Wyomings". Archived from the original on 13 August 2010. Retrieved 25 May 2010.
30. Carlson, Neil (3 July 2006). "Steam locomotive profile: 0-10-0". Classic Trains. Kalmbach Publishing. Archived from the original on 29 September 2007. Retrieved 8 February 2008.
31. "Glossary of Common Railroad Terms: D". Kalmbach Publishing. Archived from the original on 1 January 2007. Retrieved 8 February 2008.
32. "The Texas Type Locomotive". SteamLocomotive.com. Archived from the original on 25 February 2008. Retrieved 8 February 2008.
33. Hughes, Hugh (1979). Steam Locomotives in India, Part 3 - Broad Gauge. The Continental Railway Circle. p. 23. ISBN 9780950346946.
34. Paxton, Leith; Bourne, David (1985). Locomotives of the South African Railways (1st ed.). Cape Town: Struik. pp. 10–11, 31. ISBN 0869772112.
35. Holland, D.F. (1971). Steam Locomotives of the South African Railways. Vol. 1: 1859–1910 (1st ed.). Newton Abbott, England: David & Charles. pp. 92–95, 123–124, 134–135. ISBN 978-0-7153-5382-0.
36. Westing, Frederick (April 1954). "Baldwin's barnstorming behemoth". Trains.
37. Westcott, Linn H. (1960). Model Railroader Cyclopedia - Volume 1: Steam Locomotives. Kalmbach Books. ISBN 0-89024-001-9.
38. "Russian Reforms". 6 October 2001. Archived from the original on 18 October 2010. Retrieved 8 February 2008.
39. L&SWR Drummond Passenger and Mixed Traffic Locomotive Classes. Pen and Sward Transport. 2020. p. 63. ISBN 978-1-5267-6984-8.
40. Russ, David (July 1943). "Riding the Pennsy T1". Trains. Kalmbach Publishing.
41. Morgan, David P. (May 1965). "They called her the big engine". Trains. Kalmbach Publishing.
42. Herring, S. E. & Morgan, David P. (June 1966). "Instead of a 4-10-4". Trains. Kalmbach Publishing.
43. "The Jointed-Boiler Locomotives," Trains magazine, February 1945
44. "The Allegheny Type Locomotive". SteamLocomotive.com. Archived from the original on 27 January 2008. Retrieved 8 February 2008.
45. Diebert, Timothy S. & Strapac, Joseph A. (1987). Southern Pacific Company Steam Locomotive Conpendium. Shade Tree Books. ISBN 0-930742-12-5.
46. "The Challenger Type Locomotive". SteamLocomotive.com. Archived from the original on 1 December 2005. Retrieved 8 February 2008.
47. Carlson, Neil (15 June 2006). "Steam locomotive profile: 2-8-8-2". Classic Trains. Kalmbach Publishing. Archived from the original on 16 November 2008. Retrieved 8 February 2008.
48. Boylan, Richard; Barris, Wes (30 May 1991). "American Steam Locomotive Wheel Arrangements". SteamLocomotive.com. Archived from the original on 26 January 2008. Retrieved 8 February 2008.
49. "The Yellowstone Type Locomotive". SteamLocomotive.com. Archived from the original on 3 February 2003. Retrieved 8 February 2008.
50. "Union Pacific Big Boys". SteamLocomotive.com. Archived from the original on 22 September 2009. Retrieved 8 February 2008.
51. "Union Pacific Big Boy: The rebirth of a legend". Trains. 23 August 2013. Archived from the original on 12 July 2015. Retrieved 8 November 2016.
52. "Virginian Class XA Locomotives". SteamLocomotive.com. Archived from the original on 12 January 2008. Retrieved 8 February 2008.

Further reading

• Boylan, Richard; Barris, Wes (30 May 1991). "American Steam Locomotive Wheel Arrangements". SteamLocomotive.com. Archived from the original on 26 January 2008. Retrieved 8 February 2008.

External links

• Media related to Whyte notation at Wikimedia Commons

In the various names above of a 4-8-4, omitted was the letters "F E F" which simply means: four eight four.