How's your driving?

There is some initial evidence that [the “How’s My Driving?” stickers that we often see affixed to the back bumpers of trucks] are “associated with fleet accident reductions ranging from 20 percent to 53 percent.” The idea is that truck drivers who know that they might be reported for driving dangerously are less likely to violate the rules of the road.

(In the Freakonomics blog)

The post discusses a proposal to extend these stickers to all vehicles. Personally I don't think it'd work. You could phone the cops to report a crazy driver now, couldn't you?

This seems more like the "can I speak to your boss?" approach - you don't necessarily need to be convicted of a crime to be fired.