It can be difficult to spot an unmarked police car, but most unmarked police cars have a few traits in common no matter what make or model they are. Remember to keep your eyes on the road and avoid staring at a vehicle to determine if it is an unmarked car; use a passenger to assist you in the identification process.
Look for lights that can be activated for emergencies. These lights will be placed in the front grill, on the side view mirrors and along the top edge of the windshield.
Look for an antenna that is placed on the trunk of the car. Police officers need radio antennas to communicate with each other, and these antennas on the trunk can be a big giveaway that the car is an unmarked police vehicle.
Look for municipal license plates. Each state has a different municipal letter or code on the plate identifying it as a municipal vehicle. These license plates are easy to spot as they are not printed in the same format as typical license plates for private citizens. They will usually have fewer characters than standard license plates and will have the first few letters of the town or state the police car is from.