This is interesting and would make waiting at the stop light more tolerable. However, I can see how this might cause more accidents as well. Someone rushing toward the intersection (there are always crazy drivers) can see the hour glass ahead, trying to time it just right to make it to the intersection by the time it turns green. They may misjudge the timing and suddenly have to stop causing an accident, or they may get it just right as someone else in another lane is also trying to time the light just right to make their turn before the light turns red, maybe going through just after the light turns red. The two crash at high speeds. People rush through traffic lights as it is. Letting them know how much time they have makes it a race or a challenge to beat the light, becoming a dangerous game, especially among teen drivers. Like I said, interesting and fun, but there are unintended consequences that could make it more dangerous.