There was an attempt some years back to have car break lights give more information for drivers following the car.  The original system was to flash the brake lights as a speed that indicated how much braking pressure was applied to the pedal.  Faster flashes meant the driver was hitting the brakes harder.  I never saw these hit the road.  A new system which could potentially replace the 3rd brake light, uses a row of LEDs that have a few ways of displaying the amount the car is slowing down.  Read more here:http://www.physorg.com/news125773212.html