While working on some models recently, I had cause to wonder about the upper door track configuration on the USRA single sheathed boxcar. Why did it extend to the left of the door? I searched the archives and found someone had asked the question a while ago, but apparently received no answer!

I have looked in several sources (including the Lane article and White's freight car book) with no result.

Pieter Roos
Connecticut

Probably just for strength. As the heavy door moves to the left, there's
more weight borne by that part of the door track, so extending the track
distributes the load across a wider support area. I'm assuming the upper
track carried most of the weight of the door -- a "top hung" door.

Tim O'Connor

Actually,USRA single sheath boxcars had bottom-supported doors. I think
the extension of the upper door track to the left of the door was to
strenghten the top chord of the side truss at the door opening,just as the top chord of many hopper cars were reinforced in the middle area of the car.Although the hopper cars often had this added after their original construction,the USRA box cars had this reinforcement when built.Probably the presence of an opening in the side made the need more obvious.

Larry King