4-6-4-4

In Whyte notation, a 4-6-4-4^[1] 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.

4-6-4-4 wheel arrangement

The PRR Q1 6130 - the only locomotive with this wheel arrangement

Other equivalent classifications are:

• UIC classification (also known as German or Italian classification): 2CB2
• French classification: 2322
• Turkish classification: 3524
• Swiss classification: 3/5+2/4 up to the early 1920s, later 5/9

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.