How do traffic lights know when to change?
Lights That Watch
How do traffic lights know when to change?
You roll up to a red light and stop. No other cars around. You wait. And wait. Is the light just... guessing? Does it flip to green on a timer, like a kitchen egg timer ticking down? Sometimes yes — but the smarter lights are actually watching you right now.
Look down at the pavement just before the white line. See those lines cut into the asphalt — rectangular grooves filled back in with tar? That's a loop of wire buried under the road, making a big electric circuit. You're sitting on top of a giant metal detector.
