BAD BOYS, BAD BOYS... WHACHA GONNA DO WHEN THEY COME FOR YOU...

Something that I have noticed while living in Capital Federal, is the police cars which are ever present, for good reason, of course. I've been fortunate enough to never see a traffic accident (which still surprises me to no end considering the lack of traffic laws). I have never seen a police car try to pull someone over, either. But still the same, the cars always have their lights going. Why is this? And more importantly, how do you know if you are being pulled over?