Street light intersections; on top of each light has the senors that tells it to turn green?

I win, You lose, U crossdresser!

The one on top is for emergency vehicles (Police, Fire, and Ambulance)

The one embedded in the road surface (usually in a loop) is a magnetic sensor for regular traffic.

There was a story in the media this past summer of a person in Indianapolis that had bought the device to trigger those sensors, and was using it daily on his drive to work, disrupting traffic, and causing traffic delays for everyone else, due to the disruption of the cycles of the traffic lights. He was caught and the device was confiscated!

Fletcher

Different traffic lights have different methods of determining when to turn. Almost EVERY traffic light uses some type of regular scheduling mechanism to rotate the green through all intersection approaches.

The shorter answer(s) to the question you're asking, though:

1) That sensor that is above SOME traffic lights is actually a receiver for a transmitter used by emergency vehicles (fire, ambulance, etc.) in order to turn the green light in their direction prematurely and give red in the other directions.
In some areas, this can also be used by transit buses if they are a certain percentage behind schedule in order to give them the green.

2) At many intersections, there is also a sensor in the ground to detect the presence of vehicles, but it is not a weight sensor. If you see something like a metal box embedded in the asphalt, this is actually an electromagnetic sensor-- it detects the presence of cars and will use this to modify its timing.

sensible_man

Some top mounted sensors are for emergency vehicles. My area has pavement sensors, especially at lights with a specific turn arrow. If no one is in the turn lane, the arrow does not come on and allows traffic going straight to get an earlier start.

Barbara

i don't think it has a weight sensor but it needs you to be behind and close enough to the line on the road for it to sense you.

bungee

are you sure they are sensors and not cameras

kingstonsean

The "senors" are for emergency vehicles. I have seen some that are operated by strobe lights that are mounted on the roofs of fire trucks and ambulances. There may also be weight sensors embedded in the pavement so that the lights can operate out of sequence during low traffic periods.

TONY S

Street lights do not change because of any reason other than a little computer tells them to.
Street lights are made up into a computer control system; they are all calibrated to go off at a certain time, to keep traffic flowing a certain way.
Be aware of this: at night, in a bad area full of crime, a street light is a dangerous thing because if you are out and in that bad area, it makes you stop: this is how car-jackings, etc. occur.
I know this because I used to work the night shift in a big city full of crime.

nutsfornouveau

Yes. Like everything else in this world. The Senors are on top and the senoritas are on the bottom.

hazbob43

Your right there are sensors on top of the lights to change the light for emergency vechiles, as they approach the the light they can control the intersection.

There are sensors under the pavement in some intersections that change the light when a car is stopped at a red light.
It is a kinda a weight sensor.

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