[dutchmensport]

I've never heard of such a requirement for RV trailers. But, if you want to install mud flaps on your trailer, do it at the wheel well location. You are just wasting time and money putting one across the back of the RV. Some folks with motor home RV (Class A's and some C's) put them on the rear. Their tires fit closer to the rear than a travel trailer or fifth wheel. I still think, flaps at the wheel wells will do better, if you are still going to install something. The closer to the wheels something is installed, is less of a chance for a rock to fling out in weird directions, other than straight backwards.