Only one hourglass is shown at a given time. Starting from red, the pixels are all coloured in the top of the glass. These slowly trickle down to give drivers an exact reference to how much time they have until they can go. It could be great for the environment, as commuters could switch off their engines if they see they have enough time.
Once it's full of red at the bottom, the pixels turn orange and the hourglass starts again. The process is repeated until the hourglass has run out and then the entire glass changes to green. This is the part that could get a little dangerous. Obviously, would-be racers have the opportunity to rev their engines and grip the tops of their steering wheels during the orange countdown segment, and thus street racing will have entered a entirely new – and more accurate – racing level.
The process would use the orange colour before the light turns red to stop though. So in a way, it’s also safe as driver’s will be able to see exactly how much time they have left before they have to stop, and can calculate braking distances accordingly.
It’s all just a concept at the moment though, and no known government as far as we know will be adopting the system just yet.
A word of warning to any governments pondering the idea though; colourblind drivers.