Hi all. Quick one especially aimed at those with plenty of miles on the clock (and speedo!!). Am planning my 12-18 month odyssey RVing across North America. Am still to make a final decision on which type of vehicle (A-Class with a tow, or a 4 wheeler towing a travel trailer), but the question at the moment is....What is the maximum length of my vehicle which will allow me access to MOST of the roads through the National Parks and mountain regions. Yeah I know it's fairly general, but let me phrase it this way. If I travel on the Going to the Sun road in Glacier from St Mary in Montana, or take the Trail Ridge Road through the Rockies at what size (length wise) am I going to run into access problems? Some of the travel guides say as little as 21 feet, some say up to 27 feet for the same stretch of road. I'm confused. Help!!!!!!!!!! And please feel free to list your own examples of roads ANYWHERE in the states that you have had first hand experience of access difficulties. As I said I am looking at perhaps 12-18 months so I plan to visit just about everywhere.