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Several answers But 1 interesting one .... They change via metal sensors buried in the road that detact when a car is above them. See the (usually) dark tarmac diamond shapes in the road. Once metal is detected (ie car). They then decide if they should change or not. IE due to prevailing conditions ie traffic crossing the intersection or the presence of pedestrian crossing lights giving each a priority in turn.

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Q: How do traffic lights know when to change?
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Related questions

The average person will spend over 2 in their lifetime waiting for traffic lights to change?

The average person will spend over 2 weeks in their lifetime waiting for traffic lights to change.


What change the traffic lights beside the pedestrians button?

A computer that the trafic lights are conected through.


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Traffic lights change color using a timed sequence set by programmers. Typically, they cycle through green, yellow, and red to control the flow of traffic at intersections. Sensors or timers can also adjust the timing based on traffic conditions.


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No, Flashing your headlight's will have no effect on a traffic signal. The reason a traffic signal changes for emergency vehicles that have the lights flashing, is, they have a special transmitter that tells the light to change. This transmitter is connected to the emergency lights so it comes on when the lights are used.


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Did traffic lights change. i seem to remember them being green on top and red on the bottom.?

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