Under the Whyte notation for the classification of steam locomotives, 0-4-2 represents the wheel arrangement with no leading wheels, four powered and coupled driving wheels on two axles, and two trailing wheels on one axle. The configuration was often used for tank engines, which is noted by adding letters to the configuration, such as 0-4-2T for a conventional side-tank locomotive, 0-4-2ST for a saddle-tank locomotive and 0-4-2WT for a well-tank locomotive. In the 1880s and 1890s the type was also used for some famous tender locomotives.
Other equivalent classifications are:
- UIC classification: B1 (also known as German classification and Italian classification)
- French classification: 021
- Turkish classification: 23
- Swiss classification: 2/3
Read more about 0-4-2: Overview