The City of Philadelphia put up some red light cameras on Roosevelt Boulevard, a notoriously bad piece of road on which dozens of people are struck by cars each year and hundreds of people are involved in accidents. They appear to be working very well as the number of incidents has decreased markedly. What's really interesting is that the intent of the cameras appears all along to have been safety, specifically improving the safety of pedestrians. Also, lengthening the yellow light time period was tried first, then the cameras went in.
Study Evaluates the Effectiveness of Red Light Camera Enforcement in Philadelphia
That seems to be a very clear incidence of red light cameras improving safety, as well as a case where it would be hard to argue that they are there solely for revenue generation. Given that violations have gone to nearly zero, they can't be generating much cash flow.
I work in Burlington County NJ, and there are quite a few multi-lane roads with wide grassy medians separating the lanes. This makes for very wide intersections. Despite the size of the crossings, I almost never see an accident at them. The yellow light duration is considerable, and I think that plays a huge role. No red light cameras are present.
I present these as two instances where government appears to have done the right things for the right reasons. The Arizona situation does not remind me of either. Instead, the Arizona situation reminds me of the speed trap I drive through on another part of my commute. Nothing whatsoever to do with safety, just a bunch of cops in shiny new cars patrolling the only road in their area that sees substantial traffic. It's a revenue generator.