Originally Posted by achoo

"Smile, you're on Candid Camera!" while pointing to your camera tends to work even better, as noted above.

If you wind up stopped next to them, follow it up with, "Search for your license plate on YouTube in a few hours. Also enjoy your visit from the local police after I give them a copy and file a complaint. Have a nice day."

Being filmed does wonders for improving courtesy. Especially for someone in a work-owned vehicle.