I don’t understand how they work, what they’re hooked up to and how they know when to turn from green, to yellow, to red. Are they timed? Is there a sensor, perhaps a small man hiding in the pole controlling it?
In: 7
At most lights, there will be a seemingly out of place metal box on/near one of the four corners. This is the control box. Once either the timer expires, or the magnetic sensors (thought this was pressure for forever lol) that others have described say it is time to change, the light will change from green to yellow, hold for 3-6 seconds, then go to red. After all lights sit red for a few seconds, the other direction turns green. The sensors/timer for the other direction will let the controller know exactly which lights need to turn green. Sometimes opposite direction left turns only go green, other times all lights in one direction change, sometimes there is no dedicated left turn signal.
Having the control box right at the light allows authorized personnel to override the base programming depending on conditions. For example, the streets/exits leading away from a concert venue normally wouldn’t stay green for very long since traffic is normally pretty light. But whenever there’s an event, the basic programming can be overriden to allow a much longer green to keep traffic moving away from the venue.
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