I have a question about four blue lights that are hanging off the light poles on Kipling and Bowles in southwest Denver. I have never seen these blue lights anywhere else. Can you tell me what they are? - Gerrie

In the past 18 months or so I have received this question more frequently than any other, so I'll give it another go. Those lights - which have been spotted by readers at other intersections, too - are known as tattletale lights. Their purpose is to help law enforcement officers nab red-light violators.

They're synchronized with the traffic lights to indicate when the red light goes on and off, so officers not positioned in front of a signal know when it changes, said a spokeswoman for the Jefferson County Sheriff's Department.

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