Do traffic lights have sensors on the street where the car trips it and causes it to change?

Question

Do traffic lights have sensors on the street where the car trips it and causes it to change?

Answer 1

not so much anymore.

but years ago at some cross streets that connected  to a bigger road they would have a sensor in the road that would cause the light to turn from red to green so you could turn left.

the problem was the switches would wear out and it was expensive to replace them.

now days everything is run on computers & timers.

some fire trucks have a special device that change the lights red to green.

Answer 2

Some do, some are just on timers.

Answer 3

Some do but not all. When you see lines cut in the pavement usually in rectangles or circles that's the sensors. They work with magnets. When the light changes and a car passes over the sensor is set on then off when the car passes. Notice a gap in traffic (someone not paying attention). The light will soon change.

Answer 4

yes,, you can see them cut in the pavement,, It is based on the weight of the car,,, I usually pull up further because the guy behind you always does to and with two cars on there it will really speed a sensor up to change

Answer 5

some do have 'pressure pads' under the area where the first car in the line should stop.   it is gauged so it is not set off by anything very light such as a bicycle or person walking.  

others have sensors aimed from the light or the hanger to 'see' if there is an object waiting for the light.    

most city lights are on timers and those timers can be set to different intervals at different times of the day to adjust for slow traffic and rush-hour traffic.  they can also be set for weekday and weekend traffic patterns if needed.

Answer 6

Many modern signals do. They are called inductive loop detectors. That's 20 year old technology. Newer installations are starting to use cameras, but they are still a little more expensive. Like all technology, the price will come down.

Also on newer installations, emergency vehicles can turn the light green by activating a strobe light mounted on the vehicle.