In Whyte notation

Whyte notation

The Whyte notation for classifying steam locomotives by wheel arrangement was devised by Frederick Methvan Whyte and came into use in the early twentieth century encouraged by an editorial in American Engineer and Railroad Journal...

, a 2-4-4 is a steam locomotive

Steam locomotive

A steam locomotive is a railway locomotive that produces its power through a steam engine. These locomotives are fueled by burning some combustible material, usually coal, wood or oil, to produce steam in a boiler, which drives the steam engine...

 with two unpowered leading wheel

Leading wheel

The leading wheel or leading axle of a steam locomotive is an unpowered wheel or axle located in front of the driving wheels. The axle or axles of the leading wheels are normally located in a truck...

s followed by four powered driving wheel

Driving wheel

On a steam locomotive, a driving wheel is a powered wheel which is driven by the locomotive's pistons...

s and four unpowered trailing wheel

Trailing wheel

On a steam locomotive, a trailing wheel or trailing axle is generally an unpowered wheel or axle located behind the driving wheels. The axle of the trailing wheels was usually located on a trailing truck...

s.

Equivalent classifications

Other equivalent classifications are:

• UIC classification
  UIC classification
  The UIC classification of locomotive axle arrangements describes the wheel arrangement of locomotives, multiple units and trams. It is set out in the International Union of Railways "Leaflet 650 - Standard designation of axle arrangement on locomotives and multiple-unit sets". It is used in much...
  
  : 1B2 (also known as German classification and Italian classification)
• French classification: 122
• Turkish classification
  Turkish classification
  In the Turkish classification system for railway locomotives, the number of powered axles are followed by the total number of axles. It is identical to the Swiss system except that the latter places a slash between the two numbers.Thus0-6-0 becomes 33...
  
  : 25
• Swiss classification: 2/5

The equivalent UIC classification

UIC classification

The UIC classification of locomotive axle arrangements describes the wheel arrangement of locomotives, multiple units and trams. It is set out in the International Union of Railways "Leaflet 650 - Standard designation of axle arrangement on locomotives and multiple-unit sets". It is used in much...

 is 1'B2' (or (1'B)'2' for a Mason Bogie).

Examples

This unusual wheel arrangement does not appear to have been used on the mainline

Mainline

Mainline Protestant are certain Protestant churches in the United States that comprised a majority of Americans from the colonial era until the early 20th century. The group is contrasted with evangelical and fundamentalist groups...

 railways in the UK. It was however one of the configurations used on the Mason Bogie

Mason Bogie

The Mason Bogie is a type of articulated steam locomotive suited for sharp curves and uneven track, once commonly used on narrow gauge lines in the United States...

 articulated locomotive

Articulated locomotive

Articulated locomotive usually means a steam locomotive with one or more engine units which can move independent of the main frame. This is done to allow a longer locomotive to negotiate tighter curves...

s, in the USA during the 1870s and 1880s. Five examples were constructed at the Mason Machine Works

Mason Machine Works

The Mason Machine Works was a machinery manufacturing company located in Taunton, Massachusetts between 1845 and 1944. The company became famous for an early invention by its creator, William Mason, the self-acting mule, first patented in 1840. The company also later produced locomotives, rifles...

 for the narrow gauge

Narrow gauge

A narrow gauge railway is a railway that has a track gauge narrower than the of standard gauge railways. Most existing narrow gauge railways have gauges of between and .- Overview :...

 Boston, Revere Beach and Lynn Railroad

Boston, Revere Beach and Lynn Railroad

The Boston, Revere Beach and Lynn Railroad is a historic railroad that operated in Massachusetts.It was constructed as an 8.8-mile gauge narrow gauge passenger-carrying railroad to serve the Boston area....

 1883-1887. The railway subsequently received twenty-one further examples between 1900 and 1914, constructed by the Taunton Locomotive Manufacturing Company

Taunton Locomotive Manufacturing Company

The Taunton Locomotive Manufacturing Company was one of the earliest firms in the United States established especially for the manufacture of steam locomotives. Located in Taunton, Massachusetts, the company was organized in 1849 and incorporated the following year by William A. Crocker, Willard W....

, Manchester Locomotive Works

Manchester Locomotive Works

Manchester Locomotive Works was a manufacturing company located in Manchester, New Hampshire, that built steam locomotives in the 19th century. The first locomotive they built was for the Chicago, Burlington and Quincy Railroad in March 1855. In 1901, Manchester and seven other locomotive...

, and ALCO.