Good question... I wonder about this when I drive... as I simply coast to red lights and try to time my speed so I hit the lights when they are green...(much like the way I bike), yet I see dolts all the time that crowd me and hug my bumper trying to get to the red light as fast as possible... which makes no sense. The most efficient way to drive is to maintain a consistent speed, and racing from light to light is not efficient... it is just a waste of fuel and increases wear and tear on the vehicle.