Well to me there is a difference between an unmarked and an undercover car. An unmarked car is a typical cruiser-type of vehicle with a solid paint color and no lettering or seals on the doors. But you can spot them a long way off. Spotlight, antenna, wheels, etc.
An undercover car is pretty much a normal car. I've even seen 1/2 ton pick ups with a cap, with well hidden LED systems. You'd never guess it was an LEO on patrol.
I don't see them as much as I did a couple of years ago, but here there is a road rage unit on our highways. Undercover. Camaros, Mustangs, cars like that. They hunt the real idiots down, the ones going 90 or 100, weaving back and forth like they are qualifying for a race, driving recklessly and or driving to endanger. I like seeing them out there.

All is fair when it comes to the vehicles the police use. On our interstates, I'd like to see a lot more undercover cars used for routine traffic enforcement.

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Geoff. Since 1960.