Aero'd RV or worlds largest street cleaner
 

A couple of weeks ago I passed a big RV on the I5 headed north about half an hour past the Grapevine. No camera with me unfortunately, but it had a strip of fairly stiff "broom bristles" extending from the bottom edge to within an inch of the ground, covering the entire space between the tires on each side. He was doing about 70 and some of the outer bristles were waving just a little in the breeze, otherwise it was a pretty good wall and seemed to be keeping air from moving into/out of the space under the vehicle. He was following a big slow semi, and I did not get a good view of the front of the RV as we passed it, so nothing to report about the front of the vehicle.

I've seen similar bristles on semis, only behind the wheels. Presumably to capture thrown stones/road debris. Sounds like an innovative RVer.

This may be a "Road Spray" prevention device. Was the RV'er pulling a vehicle?

I believe UPS was one of the first to implement these on their semi trailers in the late 80's / early 90's (these were mounted above the wheel and hung maybe a quarter of the way into the wheel's diameter).

I asked a driver at the time what they were. It prevents rain or snow spray from interfering with passing or following vehicles -- in an attempt to prevent limited visibility. Nice courtesy -- most likely it's so they wouldn't get rear-ended or side-swiped. I'm not sure if they're using them anymore, but you can see some worn ones on the older trailers.

RH77