When you are stuck in traffic, brake lights on the car in front of you only tell half of the story.
How often have you accelerated to catch up with the car in front of you only to have to slam on brakes because the car in front of you was not accelerating but getting ready to brake. whew! close call.
Well, if you are paying attention, there shouldn't need to be a reason for close calls.
This simple innovation of just adding a "green" colored light on the back of cars to indicate when the car was accelerating would let traffic flow more like a train. There would be less congestion and less accidents. Everyone could essentially accelerate, coast, and brake simultaneously which would basically eliminate the traffic phenomenon, "shockwave".
Implementing the idea into production now would mean only some cars would have this light. NO problem. That just means you have to be extra careful around cars without the light just like you are now.
Reward: some time of recognition (like a plaque)for my idea from the person that actually gets this patented, for service to mankind and safety.