The cameras are not about safety but instead are about revenue generation.
For instance, a local town was considering putting in some red light cameras. The town performed their own historic study and found that a certain intersection had vastly more accidents than other intersections on the same road due to people blowing through the light and decided that a camera should be at this intersection.
The red light camera company did their own study which they presented to the city council which shows that they would catch way more speeders at a different intersection.
The camera went to the intersection where more violators could be caught.
If safety were the primary concern cities would take studies which have already been done on this topic into account which show that extending the yellow light by a second vastly reduces the number of accidents at traffic light controlled intersections. Instead many municipalities have been found guilty of reducing the length of the yellow light in order to bump up their revenues from red light cameras and have actually increased the number of accidents at these intersections.