"What is the small blue lights I see hanging underneath some of the Traffic signals? "
Thank you for the question, Mike. The purpose of the blue LED lights, or "Confirmation Lights," on the traffic signal mast arms is to aid law enforcement officers in catching red-light runners. The blue light comes on when that traffic signal turns red. If an officer is sitting at a traffic signal in an opposing direction, and notices a driver enter the intersection while that blue light is on, he knows that the driver has run the red light. The "Confirmation Light" will be visible (lighted) only when the Traffic Signal directly above or below is in the "Red" or "Stop" position. Subsequently, the "Confirmation Light" will not be visible when the Traffic Signal Light directly below or above is in the "Yellow" or "Green" position.
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