signs

So while driving home from DC Saturday, we passed a whole bunch of these:

Now, obviously I've seen these signs before, but.... how? The logistics just don't seem right. John said, well maybe the aircraft radios to someone on the ground to come catch you. Um, okay. But how would they identify me? Late model tan sedan? I'm sure that among the 5 lanes of traffic on the beltway, that'll be easy to spot! They can't scan your car, it doesn't have some secret government microchip in it with all your info. He could probably get close to me and follow... until there's an overpass! There's even signs like this on the Bay Bridge. If I see a helicopter trailing people on the Bay Bridge, I'm going to be more than a little concerned. It would be a very cool story to tell that you got pulled over by a helicopter though.