Some street lights don’t change unless there is a car there, how does this happen?
In: Engineering
There are sensors in the road. Look for a rectangluar perimeter patched with asphalt. That’s where your car should be.
There are sensors on the poles that can ‘see’ when a car pulls up, and that starts the sequence of light changes.
The old style of sensor is a loop of wire in the pavement. There’s an electrical signal going through the wires at a consistent frequency. When a car drives over the wire loop, the iron in the car’s frame has an impact on the frequency of the signal through a process called induction. When the frequency drops, it sends a pulse to the traffic light controller, and that’s how the controller knows that a car is waiting.
The new style of sensor is a really fancy camera on the signal arm. The camera can detect when there’s a car waiting to cross.
The sensors in the road are a PITA to small motorcycles and scooters; you are not heavy enough, or magnetic enough, to ‘trip the switch’ The cameras DO see a M/C or scooter waiting
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