Years ago I can remember switching long cuts of cars at night where the field man would be on top of the farthest car using a fusee to pass signals. It was kind of dramatic, and part of the real railroading happens after dark theory. Doubt that happens any more. I know very little about current rules, but in general I believe trainmen are prohibited from riding on top of moving cars. And most cars either never had ladders and roof walks, or they have been removed. The exception would be covered hoppers and tank cars, where access to the tops is necessary for loading or unloading. But that is done when the cars are stationary. But the ng. has a peculiar problem, the old boxcar handbrakes are on the roofs. So presumably the D&S rule contemplates the occasional need to climb onto the roof to set or release the handbrake, while the car is stationary.....and with a brake club, the way God and General Palmer intended.
JBWX