How to make racing cars start moving at the same time when the racing lights are green?

In a racing game, you want to make everything fair so that people can cheat. In my game, i want to know hoe to make the cars movable at tbe same time.(stop players feom driving a car when the lughts are red until the lights turn green) do i have to script the cars or what?

Anchor the wheels until the lights are green.