Why are traffic lights so fail safe? Why does it never happen that the North/South street AND the East/West street both have a green light?

Question

Why are traffic lights so fail safe? Why does it never happen that the North/South street AND the East/West street both have a green light?

In: Engineering

Answer 1

There’s a box nearby that tells the traffic light what to do. It literally cannot send the green signal to the lights in both directions. Since all the instructions come from the same place, there’s never desynced signals.

Also, if a traffic light fails (power outage) it becomes a 4 way stop. So even if it fails, the intersection is still safe (provided the drivers follow the rules)