To make things easy, we measured our height and use a Rv type GPS, (Rand Mcnally 7720. This is supposedly the same as the new GPS by Camping world. The great thing about using this type of GPS is that you enter the height, weight, etc. etc. information into it and it uses the information for your routes to keep you safe. It has worked great for us for some time now. But even with this we are ever vigilant to be on the lookout for low crossovers, electric lines or anything that may be low and dangerous ahead.