Well you best hope that when you "bark" at a driver while on the freeway that you dont cause an accident by startling someone because you can be charged with reckless conduct or possibly even manslaughter if someone is killed. I know how startled people can get when there is a sudden noise near them. I try to never iniate the siren or speak on the PA with the volume up when I am very near a vehicle and I think they have no clue I am there and therefore I might startle them. I have known of people to go right off the road when that happens, just a couple of months ago an officer hit the siren just as he was going by another vehicle and the old lady put it right into the ditch. Was she a bad driver? Probably. Was the officer doing something illegal? No, but I bet he will wait a second next time. If this had been a regular citizen with a siren or PA then they could have gotten in trouble. That and with todays "road rage" if you do that to enough people someone eventually will do something back, like pull a gun on you, that is happening more and more in todays uptight world. I understand people get frustrated with bad drivers but your best bet is to drive the best that you can, watch out for the other guy, and try to keep your cool. If you really cant control yourself, dont do something illegal, just use the universal sign to indicate your displeasure, however again keeping in mind what the other person may do in return.