Whyte Locomotive Wheel Classification and Arrangements

The Whyte notation is a classification method for steam locomotives by wheel arrangement. It was devised by Frederick Methvan Whyte and came into use in the early twentieth century following a December 1900 editorial in American Engineer and Railroad Journal. The notation in its basic form counts the number of leading wheels, then the number of driving wheels, and finally the number of trailing wheels, numbers being separated by dashes. For example, a locomotive with two leading axles (four wheels) in front, then three driving axles (six wheels) and then one trailing axle (two wheels) is classified as a 4-6-2 locomotive, and is commonly known as a Pacific.

Frederick Methvan Whyte, March 2, 1865 – 1941, was a mechanical engineer of Dutch background who worked for the New York Central in the United States. He is most widely known as the person who developed Whyte notation to describe the different wheel arrangements of steam locomotives in 1900.