[NCHornet]

Good topic, this actually happened to my wife about 17 years ago when we lived in CA. My wife is a very beautiful woman and has had problems with guys following her and what not. I made a point one Sat to show her how to get to every police, sherrif, or HP staion between work and home. I was happy I did because about 6 months later a guy pulled up next to her dressed in what looked like a policemans uniform and flashed a badge at her and told her to pull over. It was very dark outside and it didn't seem right to her, especially when the idiot starting yelling and screaming. Her brother is a San Bernardino County deputy and our best friend is a LA County deputy, and she knew they wouldn't be yelling at her they would be on the radio, anyway she proceeded to drive right into the employee parking of the police station right up to the back door where several cops were having a smoke. The perp kept on driving. I hate to think what might of happened if she would have pulled over.
I believe this sort of crime is pretty rare but feel you should be prepared nonetheless. In NC I have seen LOE's driving everything from Camry's. F250's you name it, and with no visible markings at all. These are mostly for the truckers but can pull anybody over. If the unit has a full light bar on top I would feel fine about pulling over. If the car just had the lights in the grill I would probably still pull over and look over the cops dress and equipment as he exits the car. If he has the Radio Shack special light on the dash, no way!!
I agree with calling 911 if you live in an area serviced by one agency, but here we have local police, sherrif, and HP so it can be difficult. If in doubt head for a police station or wait for another marked unit, but don't speed away. Better to have a pissed off cop than be dead.