Took me a few reads to understand what you were saying.
Same reason why some intersections have them and some intersections don’t. Cost efficiency.
To be honest, the correct answer to this question should be that it should trigger along both. These cameras save lives, and if you see one at an intersection, just assume it does both.
No, and also please don’t think that way. All the cameras should work.
Your questions feel like there’s an underlying reason to them and i’m not sure what it is… but just don’t try anything ya. I’ve had friends who have had their lives changed due to road accidents. Just follow the rules.