There are some nice fold up orange traffic cones on the market today that you could keep in the trunk and use. Goggle it. But I'm not sure the local "tank drivers" much care about plowing into plastic any more than plowing into your car or a crosswalk full of kids (yap yap yap .... cell phones should be banned). Clods will be clods. For about $80 you could also get a scrolling text license plate. Display a scrolling message that reads: "STAY BACK 10 feet. Hidden camera on-board, violators will be prosecuted", or something a little bit nastier. Install a bumper cam front and rear (available on the net and in RV stores). Rig it to activate when a motion detector goes off so you can record the plate number of the nasty offender.