Towing in the Rockies - Towing Capacity Safety Margin?

Interstate highways have the same grade standard in the Rockies as in the rest of the country. 06% is the grade standard to allow relatively easy access to commercial trucking. There are very FEW exceptions where this is exceeded, and then only for a short distance. State highways may be as steep as 08% and be within standards though 6 and 7 are MUCH more common. You would pretty much have to go LOOKING for grades steeper than 8% though they are out there but not on major roads.
Good luck / Skip