From what I’ve been able to glean, this is PRR’s attempt at (or documentation of) more automated box car cleaning, in this case, for GN cars.
PRR was having a hard time absorbing costs from cleaning up cars arriving dirty inside, or with significant need after unloading, and was certainly looking for solutions.
It appears to be a spray bar arrangement on a pivot. Maybe on a dedicated clean-out track with that track. I know of nowhere on PRR that they had this. Can anyone ID?
Photos: Boxcar Cleaning Equipment
A photo from the Hagley Digital Archives:
Click on the photos to enlarge them.