Union Pacific GE AC4400CW No. 6940 has wheel work done in the “Wheelhouse” at the locomotive facility at North Yard in Denver, Colorado, on December 22, 2012. A machinist carefully checks his work at the wheel lathe as he reshapes the profile of a wheelset on the rear truck of No. 6940. This unique type of lathe allows machining of locomotive wheelsets without removing it from the truck.