We become so focused on what's going on at ground level, we forget to look up. I knicked my Sunline's awning (rolled up) by a combination of road crown and leaning power pole. Since that moment I've kept an eye out for leaning traffic signs on medians, power poles sagging under the weight of lines as well as trees.
On main roads, tractor-trailers will usually have "pruned" the trees for you.
On Virginia's section of Rt. 58 near Grayson Highlands S.P., there is a rock outcropping about 9 feet above the very edge of the highway. It is covered with paint and aluminum scrapings. Yassuh, I saw that one.
Teach