2-4-4T

This unusual wheel arrangement does not appear to have been used on the mainline railways in the UK.

It was however one of the configurations used on the Mason Bogie articulated locomotives, in the USA during the 1870s and 1880s.

Five examples were constructed at the Mason Machine Works for the narrow gauge Boston, Revere Beach and Lynn Railroad 1883–1887.

Developmentally, there are two logical ways of reaching this wheel formula: to add a forward axle to a Forney locomotive to improve its ability to negotiate curves, or to add a second trailing axle to a Columbia design, notably in a 2-4-4(T) configuration to expand its coal capacity.

Four 2-4-4T passenger locomotives were built by the Czechoslovak Škoda for Lithuania in 1932 and marked as Tk class.