Quote:
Originally Posted by FireFly
Probably they have none because a battery won't tell them which colour to be at any given time...
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Well, in a situation such as a power-outage, the lights don't need to talk to other lights, or any central controller, they only need to keep operating on some failsafe program, even if it's not totally appropriate timing, so that traffic can continue flowing. Once power and connectivity has been restored, they can return to their regularly scheduled programming. Since full-blown power outages are rare, and usually don't last for more then a few hours, it would at least help to avoid gridlock, although it's likely only worthwhile for major intersections, and it would be better then turning a major intersection into a four-way stop.