any data to share ? i've never seen one in chicago. google tells me its <1%. maybe i am not using right keywords.

There are hundreds in Chicago:

https://deflock.me

Those are not for traffic signal alteration

Traffic cameras, yes. Traffic cameras that are used to influence traffic signaling? I've never (knowingly) seen one in the US.

What US cities have these?

We have one here as part of a CMU research deployment: https://www.transportation.gov/utc/surtrac-people-upgrading-...

> The system applies artificial intelligence to traffic signals equipped with cameras or radars adapting in realtime to dynamic traffic patterns of complex urban grids, experienced in neighborhoods like East Liberty in the City of Pittsburgh

Now, that said, I have serious issues with that system: It seemed heavily biased to vehicle throughput over pedestrians, and it's not at all clear that it was making the right long-term choice as far as the incentives it created. But it _was_ cameras watching traffic to influence signaling.

https://www.transportation.gov/utc/surtrac-people-upgrading-...

https://en.wikipedia.org/wiki/Scalable_Urban_Traffic_Control

Interesting, thanks!

I see them everywhere in Metro Atlanta. You can tell because there’s what looks like a little camera above each direction facing traffic light.

If you're talking about the ones I think you are, those are preemption signal devices [0] for emergency vehicles.

[0]: https://ops.fhwa.dot.gov/publications/fhwahop08024/chapter9....

No these aren’t optical sensors like those, they’re full blown cameras.

Cobb County at least on their website says they use camera sensors as well as buried induction loops.