Well we hauled a trailer(not a fifth wheel) over the Moki Dugway in Utah (Hwy SR 261):
Moki DugwayIt must be one of the most switchbacked roads around. There are a couple of videos at that link. The first one is very much exaggerated, tho I admit we didn't know what we were in for. But we enjoyed the trip up and didn't feel as if death was at our elbows. We don't have a fear of heights tho. You can see crushed vehicles off many California roads, including Hwy 101. I've heard they use helicopters to clear out the debris every once in awhile on that road.