Perhaps: The red light camera is taking video footage with a trusted and calibrated time stamp. If you see an object appear in frame in both the red light cam

Perhaps: The red light camera is taking video footage with a trusted and calibrated time stamp. If you see an object appear in frame in both the red light camera and another camera, you can use this moment to establish a timestamp for the other camera. So perhaps you see a subject walking in the red light camera (establishing time), but another camera lets you observe details about that subject.