Traffic Light Sensors

[the shelts]

I have a dumb question, excuse my ignorance.

How do traffic lights know you are there? I mean I can understand it is a sensor but are you crossing a line, is it magnetic, is it a pressure pad. I sometimes see motorcyclists waiting and waiting at an advance left turn as they are not triggering whatever it is you trigger?

Anyone.

[Mr. Bee]

Most lights that you will see in heavily populated areas are simply on timers - however there are many different kinds of traffic light sensors in the country and suburban areas.

The most common is the Inductive loop, in which there is a wire embedded in the asphalt (you can sometimes see these loops in the ground, they look like rubbery strips cut into the asphalt).

A large metal object (like a car) sitting over the loop will cause a massive electromagnetic increase in induction of the loop, and the sensor will know a car is stopped at the light.

[fedwood]

In Australia, on every road before a traffic light you can see square's cuts in the road with metal pieces in those cuts
some places have 2 in a row, im guessing they need 2 cars to set it off

[Mr Hanki's Throne]

In Australia, on every road before a traffic light you can see square's cuts in the road with metal pieces in those cuts
some places have 2 in a row, im guessing they need 2 cars to set it off

I think the ones with two in a row are trying to detect when the stream of traffic is getting close to being done and it is ready to switch to a yellow light.

[CronoGraal]

I don't know about other places, but this one route I take when bike riding here in Sweden is weird. Every single bike redlight requires you to push a button, but theres this one that has a button but somehow ALWAYS knows im coming and turns green.

I was like "cool", and all the cars gotta wait for me. :)