Are they a good idea or...not so much? Do they really save lives or do they just provide an easy source of revenue for greedy municipalities? I had some real concerns when these cameras were recently installed at an intersection I negotiate at least twice a day. If I'm cited by an officer, I would certainly remember the indecent but how could I be expected to recall or defend myself in court when an indecent occurred without my knowledge weeks before I received the citation by mail? How do they work, what is the process? Is there video as well as still photos? What happens if the light turns red while I'm in the intersection waiting to turn left? What about a right turn on red? What if someone else was driving my car? If I'm injured in a serious crash due to a negligent driver while negotiating one of these intersections, can I use the video/photo evidence in a civil suite? Google provided some answers but it seems there's no standard for these devises.
Red light camera have their place, and it's usually at intesections that have a high incidence of accidents and injuries. That's how San Francisco deploys the cameras.
The PD literally can't put a traffic officer at one location 24/7. I'm not sure what the legal deployment standard is now, but when the cameras first showed up in CA, the state legislature had to authorize the locations, or at least the specific city that was aloowed to use them. They can't be generally deployed.
What happens when the light turns red and you're in the intersection? That depends on your state. In CA, if you fully enter an intersection on a green or yellow light, generally there's no violation if the light turns red on you. The camera systems are set up to capture an image of the car tag, the driver, and the light status. And date/time stamp the photo.
Of course, like any technology, nothing is fool-proof.