Here's a link to a thread with a post by Bondo about his patent (8,408,626) on reducing drag on semi trailers:
http://ecomodder.com/forum/showthrea...-20744-11.html. They must be in production by someone because I've seen 2 or 3 going down the road in the last six months. Course, it wasn't until I found his post that I read the patent and understood how they worked. The first one I saw, I actually thought it was some kind of weather shield for unloading on an uncovered dock in the rain, sigh. Just couldn't put "aerodynamics" and "18 wheeler" together mentally :-).