To answer your question, we drove our Rialta (Winnebago Class B no longer built) over the Needles Highway in the South Dakota Black Hills. At the top of the highway is a tunnel, a very, very narrow, single lane, low clearance tunnel. We made it through going very slow, and I did not fold in the side-view mirrors. The funny thing is that I did not recall a warning at the bottom of that highway warning about the clearance.