This might be one of the most redundant signs I've come across. Of course, it's also a testament to human stupidity, because of Martin's Law (Martin's Law states Warning Signs describe how past fools have failed).
It helps to understand the terrain here. It's the top of Mauna Kea -- a maybe-not dormant volcano. There's way less atmosphere here than we are accustomed to breathing. There are only two kinds of "wild" surfaces out there. One is a deep and quite treacherous gravel. Even driving very slowly, we slid in this gravel a couple of times. Even walking. The other kind of surface is an irregular mass of ultrasharp hardened lava. I cannot impress upon you how sharp this stuff is. Any vehicle attempting an off-road sojourn would have its tires ripped out from under it in a very short time.
It would be like putting a sign in a lion's mouth reading "sharp teeth".
