In the mountains we often find stones that have become dislodged and fallen/rolled onto the road. Many times I have stopped to move something from the roadway that could be dangerous. I always wonder why so many people can drive past, swerving to the other side of the road, and not stop to render a small service to other road users by removing the obstacle. Fortunately I have not yet found something so big that I could not move it by myself.
In many places there are nets and other devices to catch falling masses. Every so often something really big comes down and I have often thought that it would be nasty to be in a Morgan under a falling rock.