# What are those Cameras on Top of Traffic Lights For?
**URL:** https://boards.straightdope.com/t/what-are-those-cameras-on-top-of-traffic-lights-for/76631
**Category:** Factual Questions
**Created:** [August 16, 2001, 9:12pm UTC](https://boards.straightdope.com/t/what-are-those-cameras-on-top-of-traffic-lights-for/76631 "2001-08-16T21:12:15Z")
**Posts on this page:** 11
**Page:** 1
### Author:  [@Wildest\_Bill](https://boards.straightdope.com/u/Wildest_Bill)
#### Post date: [August 16, 2001, 9:12pm UTC](https://boards.straightdope.com/t/what-are-those-cameras-on-top-of-traffic-lights-for/76631/1 "2001-08-16T21:12:15Z")
Are they to catch you running the light or are they some sort of counter?
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### Author:  [@therealblaze](https://boards.straightdope.com/u/therealblaze)
#### Post date: [August 16, 2001, 9:19pm UTC](https://boards.straightdope.com/t/what-are-those-cameras-on-top-of-traffic-lights-for/76631/2 "2001-08-16T21:19:07Z")
They aren’t probably cameras but sensors. Sometimes they are used instead underground sensors. No cite at this point, though.
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### Author:  [@kinoons](https://boards.straightdope.com/u/kinoons)
#### Post date: [August 16, 2001, 9:22pm UTC](https://boards.straightdope.com/t/what-are-those-cameras-on-top-of-traffic-lights-for/76631/3 "2001-08-16T21:22:24Z")
I know that the ones in my town are actually light sensors set to a specific frequency to react to emergency vehicles strobe lights. They make the light turn green for us.
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### Author:  [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)
#### Post date: [August 16, 2001, 9:23pm UTC](https://boards.straightdope.com/t/what-are-those-cameras-on-top-of-traffic-lights-for/76631/4 "2001-08-16T21:23:39Z")
Some places do have camera’s to catch people running a red light (there was just a court case on this recently where something like 300 people caught by the thing said they were denied due process or something like that…they lost).
Some cameras may be there to monitor traffic from a central control room…
Some of those are sensors are used by emergency vehicles. Emergency equipment can send a signal to the light telling it to change thus speeding their trip to wherever.
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### Author:  [@pldennison](https://boards.straightdope.com/u/pldennison)
#### Post date: [August 16, 2001, 9:24pm UTC](https://boards.straightdope.com/t/what-are-those-cameras-on-top-of-traffic-lights-for/76631/5 "2001-08-16T21:24:13Z")
I can’t speak for all jurisdictions, but here in NoVa, they’re to catch you running the red light.
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### Author:  [@Moirai](https://boards.straightdope.com/u/Moirai)
#### Post date: [August 16, 2001, 9:26pm UTC](https://boards.straightdope.com/t/what-are-those-cameras-on-top-of-traffic-lights-for/76631/6 "2001-08-16T21:26:27Z")
Often they are used for traffic volume studies, in order to provaide data to support or refute the need for changes in roads or intersections. They can also gather data on “problem” or high risk intersections.
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### Author:  [@therealblaze](https://boards.straightdope.com/u/therealblaze)
#### Post date: [August 16, 2001, 9:27pm UTC](https://boards.straightdope.com/t/what-are-those-cameras-on-top-of-traffic-lights-for/76631/7 "2001-08-16T21:27:41Z")
Ok here’s[a cite and a site](http://www.howstuffworks.com/framed.htm?parent=question234.htm&url=http://www.photocop.com/red-light.htm). So it can be used to catch red-light runners.
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### Author:  [@Mangetout](https://boards.straightdope.com/u/Mangetout)
#### Post date: [August 16, 2001, 9:28pm UTC](https://boards.straightdope.com/t/what-are-those-cameras-on-top-of-traffic-lights-for/76631/8 "2001-08-16T21:28:32Z")
In some cases they are microwave doppler units that detect vehicles approaching as part of the sequencing criteria.
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### Author:  [@Wildest\_Bill](https://boards.straightdope.com/u/Wildest_Bill)
#### Post date: [August 16, 2001, 9:43pm UTC](https://boards.straightdope.com/t/what-are-those-cameras-on-top-of-traffic-lights-for/76631/9 "2001-08-16T21:43:44Z")
Thanks for the anwers thus this far. A little more information. The cameras are mounted on a rod that is about 2 to 3 feet higher than the bar the lights are mounted on.
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### Author:  [@Musicat](https://boards.straightdope.com/u/Musicat)
#### Post date: [August 16, 2001, 9:53pm UTC](https://boards.straightdope.com/t/what-are-those-cameras-on-top-of-traffic-lights-for/76631/10 "2001-08-16T21:53:21Z")
As you run that red light…
Smile!
You’re on Kandid Kop Kamera! 🙂
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### Author:  [@Yarster](https://boards.straightdope.com/u/Yarster)
#### Post date: [August 16, 2001, 10:43pm UTC](https://boards.straightdope.com/t/what-are-those-cameras-on-top-of-traffic-lights-for/76631/11 "2001-08-16T22:43:09Z")
Sounds like a red light camera. Here in San Diego, they’ve actually had to turn them all off temporarily until some legal action is settled on them. The problem has something to do with the placement of sensors.
Also, there is the issue of ‘the picture doesn’t tell the story’ which is to say that there are some circumstances where running a light is necessary to either avoid or mitigate an accident. Yes, I know it’s probably EXTREMELY RARE, but everyone who gets nailed claims that, so who is a cop/ judge to say it didn’t happen?
And as far as the emergency vehicle sensors, we have those on our lights here too. They look like large tuning forks and stick out directly on top of the traffic lights. With an adjustable strobe light, you can actually trigger those so you get green lights everywhere you go…not that I’d know anything about that…