The last light on the tree is the dreaded foul, or red light. If you leave the starting line before the green light illuminates the red light comes on, disqualifying you. But we said leave on the last yellow; won't that give you a foul? Not exactly. Most street cars are slow enough that by the time you react and the car moves forward, the green light comes on as your tires leave the starting line. Practice will tell you when you can leave the starting line with your combination, but like we said, don't worry about reaction time right now.