[ambrop7]

Suppose the the period of lights is equal to the time expected to move from one light to the next, and each light is red/green for the same amount of time. You have a green wave if you pass the first light green and drive at the expected speed. But if you drive twice as fast, you reach the second light red instead of green. Now it would work if the period of lights was half the time expected to get from one light to the next, but why would that generally be the case?

Actually I think the opposite will usually hold: you will still have a green wave if you drive at the expected speed divided by an integer.