It depends on whether that is a point cars were going to have to brake anyway. If it is used as a slowing device in place of speed humps, then it is grabbing energy that would otherwise be wasted, and so counts as green. If it is anywhere else, it isn't.
I'm more
about the 30kW. Thirty kilowatts? (what the hell is a gigawatt?) From cars rocking a metal plate? That is enough to run several houses. They must be expecting a whole lot of cars.