A large part of the reason traffic accidents jam up traffic so badly is the inevitable looky-loo slowing as each driver reaches the scene of the accident and instinctually slows down to catch a glimpse. An ultrasound beam designed to cause a vehicle to resonate in a way that generates a loud, obnoxious sound would serve as a gentle reminder to keep things moving. A police officer could stand by the scene of the accident and zap any dilatory motorists with the ultrasonic equivalent of nails on a chalkboard. Eventually, chronic dawdlers would be conditioned to expect the sound, and would learn to focus on driving like a polite human being in order to avoid it.-- ytk, Feb 22 2011 so many ideas, so many categories... http://www.halfbake..._3a_20Rubbernecking [po, Feb 22 2011] idea to post - halfbakery traffic policeman required to direct category traffic - hic, sorry its late!-- po, Feb 22 2011 Thanks for the tip, [po]. Changed.-- ytk, Feb 22 2011 random, halfbakery