Under the Whyte notation for the classification of steam locomotives by wheel arrangement, a 4-4-2+2-4-4 is a Garratt articulated locomotive. The wheel arrangement is effectively two 4-4-2 locomotives operating back to back, with each power unit having four leading wheels on two axles in a leading bogie, four powered and coupled driving wheels on two axles, and two trailing wheels on one axle in a trailing truck. Since the 4-4-2 type is usually known as an Atlantic, the corresponding Garratt type is often referred to as a Double Atlantic.

4-4-2+2-4-4 (Double Atlantic)
Equivalent classifications
UIC class2B1+1B2
French class221+122
Turkish class25+25
Swiss class2/5+2/5, 4/10 from the 1920s
Russian class2-2-1+1-2-2
First known tank engine version
First use1912
LocomotiveTGM M class
RailwayTasmanian Government Railways
DesignerBeyer, Peacock and Company
BuilderBeyer, Peacock and Company


The 4-4-2+2-4-4 was not a common Garratt wheel arrangement. Only ten were built, all by Beyer, Peacock and Company, the owner of the Garratt patent.[1]



Eight locomotives were built for Argentina to run on 4 ft 8 12 in (1,435 mm) standard gauge.[1]

After nationalization in 1948, all these locomotives were rostered on the Ferrocarril General Urquiza (FCGU).[1]


The first Garratt locomotives to be built to the 4-4-2+2-4-4 wheel arrangement were a pair of M class passenger locomotives for the 3 ft 6 in (1,067 mm) gauge Tasmanian Government Railways in Australia in 1912. They were acquired to haul express passenger trains between Launceston and Hobart.[1][2]

The two M class engines were the only eight-cylinder Garratt locomotives in the world. They were difficult to maintain and, despite their haulage abilities and speed, both were withdrawn from service some time after the arrival of the R class 4-6-2 Pacific types in 1924. Both locomotives were scrapped and cut up in the late 1940s.[2]


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