red light cameras

hi all, old member here dont say too much but i have a question if someone will kindly answer ? how exactly do red light cameras work? tonight i found myself planning ahead i notice a red light camera set of lights on green anticipating it to turn red i slow to around 10mph only to find myself literally 5 feet from the lights and in my opinion well past the point of no return so i put my foot down as i pass the light it changes amber now pulling a 45ft trailer im worried ill have had my back axle trigger the camera, this way a tri axle traile if it helps any! its also hard to tell if i received a flash with all fire works going off. Any thoughts / opinions ?