Links to Traffic, Road Construction and Highway Conditions and Other Helpful Sites

I am interested in the effect of the length of the travel trailer on access and travel on US highways, state highways, local roads and areas. I am considering buying a TT somewhere between 29 and 33 ft and I wonder if there is some rule of thumb beyond the obvious "longer is less flexible" notion about length of TT and type of roads I cannot use. We like to travel to the mountains so this may have an effect on what I buy and where I can travel. Suggestions about where I should go to look for info. Thanks
Pat in San Antonio