Anecdotally, the small city I grew up in, in Ohio (USA), started using cameras and some kind of computer vision to operate traffic signals 15 or 20 years ago, replacing inductive loops.
I used to hang out sometimes with one of the old-timers who dealt with it as part of his long-time street department job. I asked him about that system once (over a decade ago now) over some drinks.
"It doesn't fuckin' work," I remember him flatly telling me before he quite visibly wanted to talk about anything other than his day job.
The situation eventually improved -- presumably, as bandwidth and/or local processing capabilities have also improved. It does pretty well these days when I drive through there, and the once-common inductive loops (with their tell-tale saw kerfs in the asphalt) seem to have disappeared completely.
(And as a point of disambiguation: They are just for controlling traffic lights. There have never been any speed or red light cameras in that city. And they're distinctly separate from traffic preemption devices, like the Opticom system that this city has used for an even longer time.)
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As a non-anecdotal point of reference, I'd like to present an article from ~20 years ago about a system in a different city in the US that was serving a similar function at that time:
https://www.toacorn.com/articles/traffic-cameras-are-not-spy...