There are several things that can be done without too harsh of consequences that it'd need a watertight due process. First is positive reinforcement, let peopl

There are several things that can be done without too harsh of consequences that it'd need a watertight due process. First is positive reinforcement, let people "upvote" others for good driving etiquette, then give the top 0.1% or whatever a special decal to display on their plate, or a special plate. Fakes are enforced by when, if you're ever pulled over, the officer looks up whether you were entitled to that decal and then a hefty fine if you faked it. Or maybe even officers just randomly noting down the plates to later check if it was legit, can even enforce it via existing traffic rules enforcement cameras and in both cases, fines are imposed like redlight cameras do now. Maybe even allow the driver to share the designation with their insurance company which may decide to reduce their rates. Another way would be to send some nastygrams via snail mail to the worst 1% or so, "you were voted the worst 1% of drivers by your peers". However without any other negative consequences, this might be gamed i.e "I'm so badass that I got this letter", leading to some people trying to get those letters. Since the tagging is by car, maybe give access to the insurance companies to the very worst offending cars to raise the rates for insurance on that _car_, not the driver associated with it, since someone else could be driving it.