How faulty violet streetlights came to Sioux City: ‘We intend to replace every purple streetlight’

By Mason Dockter

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    SIOUX CITY, Iowa (Sioux City Journal) — Over the last few years, defective LED streetlights in Sioux City have been showing their true colors, casting a garish purple- or violet-ish hue over streets and sidewalks.

Between about 2017 and 2020, MidAmerican Energy installed an unknown number of defective LED streetlights in Sioux City and elsewhere across the state; the lights started out bright white, as they were intended to be, but a manufacturing defect caused the light to shift from white to violet.

The phenomenon has been reported nationwide and in Canada due to the vast scale of the manufacturing defect; the purveyor of the lights, American Electric Lighting, has offered free replacements and reimbursement for the labor-cost to install them.

MidAmerican spokesman Geoff Greenwood said the utility company operates more than 6,000 streetlights in total in the Sioux City area. The violet-hue defect affected only 250-watt LED lamps, which are used to illuminate busier roadways. MidAmerican has about 950 of the 250-watt lamps in Sioux City, though the defective LEDs were not necessarily installed in every last one of these light-posts.

Greenwood estimated that around 500 defective lamps have been replaced in Sioux City during the last few years. The exact number that remain in service in Sioux City not known; it is distinctly possible that some of them continue to give off a white light, or something close to it, and may not begin to change color for some time.

“We intend to replace every purple streetlight,” Greenwood said, adding: “We have no doubt there are lights that have yet to change to purple.”

The defective lamps should have lasted approximately 100,000 hours, or around 20 years of nighttime service, Greenwood said. In reality, their service-life was but a small fraction of that.

MidAmerican, which has been aware of the violet LED issue for at least two years, aims to replace a faulty streetlight within about a week of receiving a report of it, Greenwood said — but at times this can be delayed by inventory issues or other unforeseen impediments.

“Unfortunately, there has been quite a backlog by the manufacturer, to provide us with replacement lights,” Greenwood said.

“Chances are we know about it, but it’s entirely possible that we have not yet realized that it has changed over to purple,” he added. “Once we learn of a purple streetlight, then we will add it to the list of lights that we need to replace.”

Anne Westra, communications and public engagement specialist with the City of Sioux City, said by email that the city has been aware of the violet streetlights for about two years; the city, she said, has directed citizens to report defective streetlights to MidAmerican.

Some of the most prominent and intensely violet streetlamps still in service in the Sioux City area at the time of this writing are in the northbound lane of Interstate 29, near Exit 1 at Dakota Dunes, just north of the South Dakota border. Scott Rabern, a road design engineer with the South Dakota Department of Transportation — which operates lights above interstates and state highways — said in an email that the department is aware of roughly 100 defective LED lamps in the state.

The South Dakota DOT first became aware of the issue in February, Rabern said.

Rabern said the DOT does not have any estimate for when all the defective LEDs will be replaced, but the department is keeping tabs on the reported locations of defective lamps to get them replaced.

“Anyone who views LED lights that appear purple may call any SDDOT office to provide the location information,” Rabern said by email.

The Iowa Department of Transportation’s district office in Sioux City told The Journal there have been no known reports of violet LED lights in its district. (As is the case in South Dakota, the Iowa DOT is in charge of the streetlights over interstate highways, including I-29 in Sioux City.)

LED streetlights have, gradually, been replacing the once-ubiquitous sodium vapor streetlights (the lamps that cast a familiar, intense orange glow); though a number of them are still in service and a few may remain in inventories, sodium-vapor lamps are no longer manufactured. In time, orange streetlights will go dark completely.

The LED replacements — at least, the ones that aren’t defective — have advantages over the old sodium vapor lamps, Greenwood said.

“Those are the types of lights that we now install, are LEDs,” Greenwood said. “LEDs are a superior product, they are more efficient.”

The violet color of the defective lamps is actually closer to the “natural” color of LED lighting. White light (or various shades thereof) in an LED lamp is achieved by the application of a special phosphor coating, which shifts the light from a blue-ish or violet-ish hue to white, Greenwood said. When the phosphor coating failed in the defective lamps, the LEDs reverted to their true color.

“They are not operating as designed — we ordered lights that should appear to be white, and that’s how they start off, but then when they change to a purple hue — that’s not the product that we ordered,” Greenwood said.

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