+1 for Breacherup. The cop should be in uniform, not in a baseball cap and t-shirt the just says "police". 99% of the time official police lights contain BOTH RED and BLUE lights. if it is just one color, something is up. Also I would say 80% of the time cops and troopers work alone. There is a chance he has a partner or he could be training a rookie, but if 3 or 4 guys jump out, something is definately up. Usually the only reason an unmarked car would pull you over is if your speeding (speeding trap). In PA all police must respond with a marked crusier if requested, usually the unmarked car would just pull the speeder over and just sit there until a marked cruiser shows up. If an unmarked cop pulls you over, and approaches your car. I would make sure I was in an well lit area and get on the cell phone and dial 911 and request a marked cruiser, keeping the doors locked, engine running, windows up, but with a tiny,tiny crack open so you can talk to the guy. If I had no cell phone, tell the guy that you need him to call in a marker cruiser. If he says that he can't get a marked cruiser, something might be up, tell him you want to drive to the nearest police station. He should be ok with it, if not something is up. Take off and drive to the nearest public place with a phone and call 911. The only thing a real cop in unmarked car might ask you for is to turn off your engine and for your license and Registration, (you can slip that thru the crack in your window if the guy is a real cop, he should not be offended by it). A cop in an unmarked car would not ask you to get out of the car or roll down the window until the marked cruiser shows up unless you did something extreme (like you got a dead guy on the hood of your car, or a crack pipe in your mouth). If he trys to open a door or get in, take off.