Well, I can not figure out the purpose and really not sure how to stop this, besides spending the night and calling the Police. But my plan (this is from a non-truck owner and never off-roading ever guy) was to dig a hole on one side of their ramp. My logic is if I dig it down far enough the average truck will not be about to get up the hill? I was also thinking about installing posts but I am afraid someone is just going to rip it out of the ground. So seriously email me if you have any knowledge of preventing it or if you know the purpose of this event.