Diesel disruptor
Four U25B demonstrators climb upgrade on the Northern Pacific near Blossburg, Mont., in 1961. The U25B brought GE into the heavy diesel market, and within a few years the company had eclipsed Alco for the No. 2 spot among locomotive builders. General Electric photo
They were probably a dynometer car (to measure the pull of the draw bars) plus two support cars (maybe sleeping space for the officials and others).
The NP Historical Society probably has more information to share.
Jim Uttley
What is the reason there is passenger cars just behind the engines????