Pull up to an intersection at a red light, eyes ahead, scanning left and right.
Maybe the blue light from the traffic signal caught your eyes, like it did for Bob Thompson of Mill Creek.
“What is the blue light that comes on in the back of traffic lights when they turn red?” he wrote to The Daily Herald.
It’s a common question, as evidenced by internet search results.
The blue light, a dot compared to the full orb of a traffic signal’s green, yellow and red, is for traffic law enforcement. When that blue dot shines, it means the signal is red.
It helps law enforcement officers know if a driver runs a red light, which they may not see from other approaches at the intersection.
The “telltale” or “confirmation” lights are popular across the county, state and country. The Herald mentioned them in 2019 as part of Everett’s consideration of red light cameras and as far back as 2007 when the traffic engineer for Marysville said the devices were used as part of its red light-enforcement program.
Even PBS reported on the devices in 2019.
They’re not on every signal. Instead governments prefer to install them at intersections known for drivers running red lights.
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