Very easy: US HGWY 6 over Loveland Pass for back-country skiers (Only in the winter, and only to the top of the mountain). Make sure to find a large pull-off area on a straight stretch of road.
'''Note''': When hitchiking in Western Colorado dont don't get dropped off around Bunea Buena Vista or Canon City. There are prisons in the area and you are likely to be stranded for long periods.