These blue lights turn blue when the traffic lights turn red. From a distance, it give emergency vehicles using advanced EVP systems using infrared signals to the emergency vehicles to sometimes approximate when to turn the light green, but also when the light will change, though limited to, especially when there's heavy traffic, as to not create traffic accidents, but it's to aid in response times. It's also used by law enforcement to determine if someone runs a red light, not just video cameras alone, but especially at night where the light is more visible and is seen from a distance perspective, to determine the particular vehicle crossing a red light.