What you have to consider is what information a cop has that you don't. I did not like working traffic. However, good arrests of really bad guys have originated from traffic stops,
Randy Kraft being but one.
Cops look for those who are out of the ordinary. Especially in the morning when people are rushing to work, its common to see drivers eating, shaving, putting on make-up, reading documents while driving, moms trying to get bottles in crying babies' mouths, all of which are illegal. It's the dude that was going far out of his way to not get pulled over that attracted my attention. I once saw a dude on a beach in the summer wearing a long-sleeved jacket. It was obvious that he was hiding track marks. He got my attention. Now had it been winter, I probably wouldn't have looked twice at him.
