Almost everyone knows what the colors red, yellow and green mean on a traffic light, but what about blue? In some parts of the United States, drivers have spotted the addition of a bright blue light mounted near traffic signals and have been totally confused about what they mean. A blue light is designed to help law enforcement monitor whether the traffic signal is displaying a red light. Its whole purpose is to let police know if someone has run a red light. You won’t see the blue light in an extra circle on the traffic light, but typically mounted above the traffic signal. These blue lights are electrically linked to red lights on one or more of the approaches to the intersection. Police use them to observe the red light when they're in a location where they can't actually see it. So, when the red-light traffic signal indicator is illuminated, so is the blue light. The blue light makes it more efficient, since you need fewer officers to keep their eyes on the same stretch of road. They also reduce the need for officers to cross the intersection against a red light to pursue a driver who has run the signal. The color blue was chosen to avoid sending mixed signals. Since blue isn’t recognized as a standard traffic signal, drivers are less likely to mistake it for a signal telling them to stop, slow down, or go. You may not see a blue light, as they are scattered at best. They're most prevalent in Florida and Colorado. What should you do if you see one? Unless you've just run a red light, you need not do anything. If, on the other hand, you have blown through a red light, you should probably check your rear-view mirror for a police car.
