Curious Louisville

Traffic signals. You barely notice them until they’re not working. That’s a nuisance in general, but especially annoying — and potentially dangerous — in bad weather.

Listener Matt Trippe wanted to know why thunderstorms knock out traffic signals so frequently. Compared to other places he’s lived, it seems like a bigger problem here.

There are a bunch of things that could send a traffic signal to flash, which is industry jargon for the safe mode in which drivers must treat flashing red lights as stop signs. According to Stacy Klein, who supervises electrical maintenance for Louisville Metro, the culprit is often power or — more accurately — the lack of it.

When the power to the traffic signal’s controller cabinet goes out, the computers inside it send the signal to flash. And the power doesn’t have to be out for long.

“If the lights flicker in your home, that could be enough,” Klein said.

Other possible causes include rogue tree limbs taking down overhead wires and lightning strikes damaging components inside the controller cabinet.

But Trippe had another question, too. Did the city hire a contractor that used cheap wiring?

I had to figure out a few things: Who owns the traffic signals? And is the wiring they use “cheap?”

Listen the story in the player above to hear my findings, obtained through interviews, an open records request and a traffic signal maintenance ride-along.

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Amina Elahi is WFPL's City Reporter.