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Traffic Signal Sensor?
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Traffic Signal Sensor?

What is that little camera looking thing on traffic signals?

OORAH! It's a Marine thing
its in the ground

tfmn is right

Tom Schupy
to allow emergency vehicle to change the red the cross st. and green for the traffic going in the direction as the emergency. vehicle.

Christian C
I think they are radar boxes that sense when a car arrives at the lights. Some traffic lights use these and others have sensors hidden under the road. These pick up when a car pulls up at the lights so they know when to change. Especially at 3 in the morning when you're the only car on the road.

I know exactly what that little camera is for and it cost me $75 to find out. I received a citation in the mail from the Red Light Photo Enforcement Program in the county where I live. They had a picture of the back end of my car, license plate and all, driving through the intersection after the light had already turned red. I had to pay the fine because, obviously, I couldn't protest--they had a picture. I remember that day very clearly. I had a lot on my mind, I was super stressed, and I didn't even notice the light until I had already gone through it. That was a bummer to have to pay that fee, but I sure know about that little camera now. It's good for safety because I'm more careful when I drive now, I don't want to pay $75 ever again!

There are several different reasons for the "funny looking boxes" on traffic signals. Here are all the purposes I know of. I know I am repeating the ones already mentioned.

1. Red light enforcement.
2. Emergency vehicle override devices
3. General traffic detection for changing the signal.
4. Speakers for the blind to know when it is safe to cross.
5. Surveillance cameras for traffic control or emergency services centers to monitor traffic flow and accidents.
6. Changeable signs for traffic conditions such as timed NO TURN restrictions and railway crossings.

The sensor on top of the signal head is for emergency vehicles. The sensor counts the strobes of the Emergency vehicle lights and make changes to the traffic signal controller to change the signal for that Phase(direction of traffic). There are a few different ways the controller can go, the most common is to shut down all other phase of traffic to allow the emergency vehicle to get a green light. Some systems will cause the signal to flash green for the emergency vehicle and red for everyone else. Some times the controller is set to lock on the green light for that emergency vehicle so it can get through intersection like a fire truck.

Those are sensors for emergency vehicles. Many fire department, EMS and police vehicles are equipped with a device the is activated when the emergency lights are on. When the emergency vehicle approaches the intersection, the sensor on the pole picks up the signal, and the normal light cycle is changed, to allow the emergency vehicles to have a green light.

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