The Pennsylvania Railroad's Q2 class were the only locomotives ever to use this arrangement.
These were duplex locomotives, in which both sets of driving wheels were mounted in a common, rigid locomotive frame.
This locomotive design was a further development of the highly successful 2-10-4.
The divided drive, or duplex arrangement, allowed for higher speeds with less damage to the track.
A proposed design for the Lehigh Valley Railroad was done but it was never built.