Neither drivers green OR red light would come on until BOTH cars have left the starting line. The last car to leave the line would not know whether the other car had red lit or not until AFTER they had left the line themselves. I have the slower car in Footbrake 90% of the time, being that I race a '67 Valiant street car that runs 8.30 @ 84 mph in the 1/8th mile. I would LOVE to see this rule enacted, as my win percentage would increase, I'm sure. But I am NOT holding my breath while waiting.