This doesn't make sense for automobiles. The automobile going up the hill has the advantage of gravity to help it stop. The automobile coming down the hill requires far more energy and better equipment to stop.
This regulation would appear to be left over from the era of the horse and buggy. For horse and its load to stop on the way up the hill and then restart would've been much more difficult than for the horse and vehicle coming down the hill.
Which is the subject of this blog. Many of our modern day behaviors are byproducts of earlier technology.
I am told that the railroad gauge for track in the United States came from England which in turn came from the Roman era that established the width of vehicle tracks based on vehicles pulled by two horses side-by-side.
This ancient technological reality is evident at the Russian-Chinese border where the train cars have to be put on new wheels to go from one country to the other. Really from one ancient Roman civilization to another ancient Chinese civilization.
The persistence of technological tradition is of great interest. We certainly know it every time we use a computer because the keyboard is tied to the earliest problem that typewriters had of conflicting letters converging on the type roll.