[SamAdams76]

Defensive Driver training courses call it the “3 Second Rule.” The light changes you count to 3 before you move; the car in front of you begins to move you count to 3 before you move.

That's not it at all! That has to do with following distance. You stay three seconds behind the car in front of you (at current speeds).

In the Northeast, there is a one second rule. If you fail to move within one second of a light turning green, you will get honked at by the cars behind you.

[TankerKC]

You are correct.

There is a heavily traveled left turn right before my house. It stays green for 15 seconds. If you sit for 3 seconds before going, you're a selfish prick.

[.30Carbine]

Thank you for the correction.