In the United Kingdom, a unique speed sign called a Speed Indicator Device (SID) successfully slows down speeding motorists.
Using positive driver feedback in the form of a smile, many speeding drivers passing SID slow down to turn a frown into a smile.
In Scotland and England, these signs reduce the number of speeding motorists by 50%.
It goes to show you a smile is more effective than the threat of a fine and points. Would seeing such a sign slow you down?