
In Whyte notation, a 2-4-6 is a steam locomotive with two unpowered leading wheels followed by four powered driving wheels and six unpowered trailing wheels. This wheel arrangement is only documented as being used for tank locomotives; no 2-4-6 tender locomotives are recorded.
Other equivalent classifications are:
The equivalent UIC classification is 1'B3' (or (1'B)'3' for a Mason Bogie).
This unusual wheel arrangement does not appear to have been used in any country except the United States. The following railways are recorded as having used locomotives with this wheel arrangement: