In a recent study, drivers managed to speed much less when offered a $25 reward.  The catch? Each time the driver went over the speed limit they lost a little bit of their reward.  It's funny how the human brain does everything possible to avoid punishment, even one as small as six pennies.

The study used GPS devices installed in the participants' cars and gave immediate feedback about the vehicle speed.  So, if the driver crept a few mph over they knew they had just lost a little money.  Enough "beeps" from the GPS unit helped people remain below the limit and keep all their money!

NPR's got the story.

Now we won't need 100 mph speed limits!