Next page is our salute to road food. I get this question a dozen times at every RV show and RV seminar. Maybe it's because you haven't asked the correct question. What may seem like a simple question, has a complex answer. It should not be relied upon as a comprehensive legal advisory.
Laws change periodically.
Always check with authorities in the states where you will be driving. Visit this website for a quick reference to height and width limits listed by state. If a truck was hauling a load wider than that, it required a special permit, and sometimes an escort vehicle. The trucking industry saw this as an opportunity to haul bigger loads in wider trucks. Buses, even local transit buses and school buses, are now being built on the 102-inch platform.