Perhaps I should have said up to 12,000 feet but I can tell you from personal experience that from 11,000 feet to 12,000 feet doesn't make that much difference. Here in Colorado, I can draw a 300 mile semicircle west of my house and cross over at least 18 passes over 11,000 feet that are easily ridden on a road touring bike. There are also a vast number of passes that can be ridden on a mountain bike. I'm not sure of that number, however. Four of those passes are over 12,000 feet and one of them is only 8 feet short of 11,000 feet. I've actually toured over 6 of the 18 passes.

I've noticed in my travels that the forested areas of the eastern US have a lot of really steep roads...and not all of them are short. Some seem to grind on for miles. Here in Colorado, the roads generally don't go above 7%. I blame the steepness of the roads in the eastern US to the fact that they can't "see" the mountains and just run roads in as straight a line as possible. In Colorado (and the rest of the west), we can see where the roads go and people said "no way am I going up that!" and they had to build roads with shallower grades.