To protect themselves from prosecution when the red light camera gives a faulty reading; for instance, when pulling a trailer and yellow turns red while the vehicle is still in the intersection, making its turn, having to wait for oncoming traffic to pass first.
Drivers will also have to worry about the driver in front of them suddenly stopping as soon as the light turns yellow and, conversely, a driver behind, who may assume that that the driver in front will not suddenly stop the second that the light turns yellow.
An alternative could be to have the lights green long enough so that drivers arent pressured to race through the intersection, extend both the yellow light time and the time of the crossing red light so that it doesnt turn green as soon as the opposing yellow turns red. This discourages drivers from not slowing down when the light is red in anticipation of getting a green light and create the likelihood that any crossing driver will stop first.
On my corner, this set up has cut down accidents significantly.
A large percentage of cars now are now equipped with their own cameras so accident fault can now be determined without having to install traffic light cameras, if the primary purpose is to reduce the rate of accidents and not create a fund raiser for the police department.