It's all about revenue, not traffic safety.
I like to give politicians the benefit of the doubt and figure it's intended to be sort of about safety (maybe 10%).
Another gripe (valid complaint) about cameras in my neck of the woods is that they mostly catch folks who roll through reds while taking a right turn. This is a low accident causing act; people who slow down enough to check to make sure they are clear before proceeding don't cause anymore accidents than those who stop completely and then proceed to right on red.
The sudden addition of traffic cameras led to some folks who would be driving their usual, safe route, suddenly remember they were on camera, and slam on their breaks, which led to rear end collisions. So the anti-camera crowd now had valid data that cameras sometimes increase collision rates.
The intersections I'm thinking of were recently fixed by installing lights with blinking Amber arrows and adding a special right-turn lane. This greatly improved traffic and reduced accidents much more than those silly cameras ever did. The cameras are still up though, a testament to the ratcheting of the surveillance state on the people.
My point is we can improve safety and traffic flow by better traffic design and saner speed limits (90+ thru Utah, the Kansas Turnpike, and much of Texas is entirely reasonable in good driving conditions) while not infringing on the modicum of privacy we still enjoy as we try to go about our days unmolested.