US 6 Loveland pass

I do know of an instance where a guard rail stopped a truck from going over the side. ....

We have a hill here that is a 15% grade. At the bottom, it turns. A winter storm had moved in. DOT didn't get up there in time to do anything about the road. This truck came down that hill. Got to the bottom. It couldn't do anything but keep going. Couldn't stop. Couldn't turn. No nothing. He hit that rail. Took out about 100 yards of rail. It stopped him from going over the edge. I saw it the next morning. Couldn't believe all this guard rail. Mangled up in a huge heap. On the other side of the road.
I found out later. The truck belonged to DOT also. It was all DOT's fault, all around.
Admittedly the truck was empty. I never thought a guard rail would do that much. It did. The driver was fine.