My old unit was 10'6" at the A/C, and I think there was only one instance I had a close call, and a couple times I had to go around to avoid a low clearance. The new Georgetown is 12'1", so I'm a little more worried. I often travel through the tunnels along US 6 in Clear Creek Canyon near Golden to get to Rte. 119. The tunnels aren't marked, but signs along the route say trucks over 13' are prohibited. They don't say, however, whether there is a margin in that 13', or where that is measured, center or edge of lane. I would still be nervous going through those tunnels, but the alternative, going through Central City, is out of the way and has too much traffic.
Gary Shapiro, 2011 Georgetown 29' Class A
Dash, Molly & Lily - now at the Bridge and forever in my heart
Shadow - 4-year-old Greyhound
Hannah - 1 1/2-year-old GSD rescue