a) "There is someone who is looking out for the people and keeping us safe"
b) "Great another person out to get people, and make his quota"
Do you have a different impression if the cop is easy to see, or is in a partially/totally obscured possition?
It partially depends on where the cop is located. If he's near a school while school is getting out, they're there for the kid's safety. I've actually seen a cop walk out in traffic to stop a car going too fast as the kids are being let out.
Now, if it's on the highway or on a random backroad, I feel they're there just to get the money. Where I live there used to be a speed trap where you almost always knew a cop would be there. It was a well known fact that a part of the city budget was specifically from that speed trap. Luckily that's gone now, but I still can't help but stay slow in that area. There's also a spot on the highway where I do always expect a cop to be...