[jonhohle]

At least in Arizona where the top end is 75MPH, speed limits on highways seem reasonable for the environment. There are plenty of opportunities to go careening off the side of a mountain or into oncoming traffic because a ¼ mile earlier nothing would suggest that the natural momentum from the grade of the mountain road was excessive for the upcoming switchback.

So they could set up some arbitrary obstacles to slow people down prior to the natural contour of the terrain, or, you know, throw up a sign which indicates a safe speed for the upcoming section of highway.