If that area is susceptible to rockslides there should have been something called a rock fence or slide fence. When a rockslide is detected, it either sends a radio signal to the train to stop or it removes the wayside signal and that would stop the train. They are commonly used where rockslides have occurred in the past. If I'm not mistaken, there is an FRA (Federal Railroad Administration) rule that this type of protection is mandated in areas of past rockslides.
Since this seems to be a substantial rockslide, I doubt this was the first time this has occurred in that area.
A quick look-see and slide fences have been in wide use since 1922, so that area should have been protected.
