4-6-4-4

In Whyte notation, a 4-6-4-4 is a railroad steam locomotive that has four leading wheels followed by six coupled driving wheels, a second set of four driving wheels and four trailing wheels.

Other equivalent classifications are:

UIC classification: 2CB2 (also known as German classification and Italian classification)

French classification: 2322

Turkish classification: 3524

Swiss classification: 3/5+2/4

The sole example of this arrangement was the PRR Q1. This locomotive was essentially a prototype in the development of the PRR Q2, a 4-4-6-4.