What is the most practical method of preventing rock slides and rockfalls on dangerous mountain highways?

There are several practical methods of preventing rock slides and rockfalls on dangerous mountain highways. First, you can reroute the slide based on completed geologic engineering studies, next, you can construct drainageways in order to contain any type of runoff sliding, next, you can build walls on the uphill side of a roadway that is at risk, and finally, you can 'stitch' a slope that is prone to sliding.