Are there really sensors under the streets?

Question

Im just trying to prove a point to my friend because he doesnt believe me that there are sensors...

But also can you tell me how they work if you know?

Answer 1

There are sensors under the streets to detect cars at traffic lights.

Some lights are just on a schedule where they stay green for so many seconds then red for another amount of time. Other traffic lights have those handy sensors so that cars don't have to sit and wait at a red for a minute or two when there is no cross traffic coming.

I think they are triggered by a vehicle's weight. My younger cousin rides a Harley sometimes and she says that at certain lights she has found that if she is the only vehicle waiting at a red light, it won't change (she's tiny and it's a small little Harley, so it must not be enough weight passing over the sensor to trigger it). She claims she has to either back up to the sensor and sit there for a few seconds (sometimes you can see where they added it, as a car-sized rectangle in the pavement back from the light) or just make sure there is no oncoming traffic and no cops and blow through the red. If a car or truck pulls up behind her then the light will change.

Answer 2

If you mean pressure sensors for the lights, then sometimes there are. Usually you'll see weird patterns up near the intersection and occasionally some rounded metal rectangles or other strange shapes inlaid in the asphalt.

Answer 3

they are not triggered by weight.  they are trigged by electrical sensors that are disrupted by the cars emf field