Why faulty street lights are turning cities purple and why it’s a concern

Street lights in many major cities have turned purple. Was it just an accident or a warning of the coming chaos?
Well, maybe not the whole sky. But enough has been seen. A row of street lamps—hundreds of thousands—suddenly changed. What was once white, bathed in moonlight, is now blue, mauve, and even purple. Objectively speaking, they are no less intelligent. But purple doesn’t brighten the sidewalks the way white does. Vancouver’s spectrum turned to the left. It looks pretty good. It’s not dangerous, especially. It is very strange.
Hence the disturbed calls to the city. After all the hype in Vancouver, they rolled out the truck and decided to replace the chromatic aberration, although the headlights are still new. Like most other cities, Vancouver has switched over the past few years from old sodium vapor street lights to LEDs. The new light bulbs, which are basically sets of computer chips that convert electricity into light, are cheaper, use less energy and last longer. LED street lights should shine for most of the next decade.
Unless they do. Because Great Purpling doesn’t start and end in Vancouver. The reports are for 2020 and across the hemisphere – Wisconsin, North Carolina, Florida, New Mexico, California and even Ireland. “This is something we started seeing about two years ago,” said Jeff Brooks, a spokesman for Duke Power, who is responsible for streetlights in the Carolinas and parts of Florida and the Midwest. “People called me and asked if it’s because it’s Halloween or because their football team in the area wears purple.”
It has nothing to do with ghosts or football. This is not a grand conspiracy, although it is a sign of the times that many are seeing the effects of 5G or government oversight in synthetic twilight. Nothing suspicious is going on here. But still: street lights should not spontaneously change color.
So I did some digging. The violet light mystery seemed more mundane and unsettling than anyone could have imagined, an indigo-indigo mood-checking light illuminating all modern infrastructure. When LED street lights start to change color for no reason, it’s a visual signal that we may need to rethink how we build our future.
In a sense, you could imagine the whole idea of ​​modern human society with a light bulb burning overhead. Few technologies have played such an important role in shaping the world as we know it. In the 300 years of human history, from 1500 to 1800, the cost of lighting a lamp – of any kind, from candles to whale oil and coal – has remained virtually unchanged. But around 1800, prices began to fall sharply.
Industrial Revolution cities were first lit by gas lanterns – their mantles, the parts that contain the bright flames of the gas, were the first large-scale use of rare earth metals vital to batteries. About a century later, electricity dominated indoors and city streets. First an arc lamp, then an incandescent lamp, neon lamps, fluorescent lamps, mercury vapor, sodium vapor. LEDs have been hot new for the last few years, in part because they don’t get hot. They convert electricity directly into light – no intermediate steps, only direct electron-photon exchange: Damn! Very economical and environmentally friendly. Today their annual turnover is 20 billion dollars.
By the late 2000s, cities around the world were replacing traditional lighting fixtures with modern, high-tech LEDs. Generally speaking, it is white light. But as anyone who has painted a bathroom knows, not all whites are the same. For the technical reasons of quantum theory and the bizarre psychophysics of our eyes and brains, scientists measure the color of white light in kelvins, or “color temperature.” Higher numbers are more blue, lower numbers are more yellow and red. Many cities have chosen 4000K, the moonlight of high-end sports car headlights and, not coincidentally, one of the easiest and therefore cheapest white LEDs to produce.
It’s a stunning transition from the more romantic orange glow of sodium vapor. Less Paris under the moon, more Porsche on the highway. “Every new lighting technology that is introduced causes panic until people get used to it,” says Sandy Eisenstadt, an art and architecture historian at the University of Delaware. “Usually it’s about color, sometimes it’s just about brightness. Even the introduction of gaslighting has attracted a lot of attention in this regard.”
In the case of Duke Power, only about 1% of the installed LED streetlights were affected by the color change. Despite this, around 5,000 lanterns still operate throughout the country. So what made purple reign supreme?
It turned out that the problem was upstream. Over the past decade or so, the LED lighting business has consolidated and the US market is now dominated by a company called Acuity Brands. Every purple city that has answered my question or has a public report on the matter has purchased LED lights from Acuity. From 2017 to 2019, Acuity seemed to run into trouble — exactly where technology and globalism intersect.
As Isaac Newton discovered with a prism in 1665, white-yellow sunlight consists of a rainbow full of the visible spectrum. Where you draw the dividing line on the spectrum – and what colors you name – is very subjective. But combine all those wavelengths of light and you get white again.
However, you do not have to use all wavelengths. If we mix equal amounts of red, green, and blue light, our eyes perceive it as white. Now red and green LEDs have been around since the middle of the 20th century. But blue proved to be such a challenge that its inventor, Shuji Nakamura, received the Nobel Prize in 2014. Blue LEDs have a narrow wavelength, which allows the use of various modern technologies, from Blu-ray discs and flat screen displays.
The big breakthrough in blue light has also allowed engineers to produce white LEDs that are both bright and cheap. This is because they no longer need red and green to turn white. Blue LEDs immersed in a yellow phosphor do their job under a thin ceramic and glass lens. Our eyes perceive a mixture of blue and yellow as white. It’s a big leap to simply wrap a blue LED chip in an intricate package of glass, sealant, solder, wires, and more. Make it cheap and reliable enough and you’ll have a global business.
However, it would be instructive to delve into this last part. “There could be hundreds of patents for LED packaging design,” said mechanical engineer Michael Pecht, director of the Center for Advanced Life Cycle Engineering at the University of Maryland. “The chip is really reliable. The problem is in the packaging.
what’s question? Acuity and Purple City are not completely transparent on this issue. It turns out that most of the wobbly street lights are made by an Acuity sub-brand called American Electric Lighting. Acuity spokesperson Neil Egan told me that “the said ‘blue light’ effect appears in a small percentage of AEL luminaires whose components have not been sold in years.” As to the reason for the purple color, he said it was “a phosphor shift observed years after the original installation”. In other words, there is something wrong with the fancy packaging around the LED.
Representatives of the affected cities provided more detailed information. “The purple street lights are the result of peeling off the phosphor coating of the LEDs,” Vancouver spokeswoman Fiona Hughes said. Brooks of Duke Power points to the same reason. “The luminaire has a layer of laminate that gives it a white look,” he said. “When the laminate starts to decompose, it causes a color change towards purple.”
But what causes stratification? The most likely cause is thermal damage. The phosphor layer in the LED housing is very sensitive to temperature changes. Even the slightest mistake in assembly or installation can make the LED more prone to heat. This causes the edges of the phosphor coating to curl, the LED chips to peel off, and more of the natural blue color to bleed. It can also change the chemical structure of the phosphor itself, which in turn will change the color emitted by the LED.
Of course, you can avoid most production problems if you are willing to pay for quality. Electronics reliability specialist Pecht worked with Philips many years ago when the company was a leader in the LED market. “They did a lot of long term testing at higher voltages, humidity, etc., and I think their device could last maybe 10 years,” Pecht said. “But their equipment is probably the most expensive equipment on the market. They can be very reliable, but you have to buy quality equipment.”
Acuity LEDs are not the most expensive LEDs on the market. But that doesn’t mean the company itself created the problem. According to Acuity 10-K’s filing, the company manufactures some precision components and assembles them at 19 factories in North America. But Acuity orders the LEDs themselves from “third party suppliers” in Asia. These vendors tend to mass-produce products, trying to be as efficient as possible without infringing on patents for high-quality, expensive versions. Sometimes this results in low quality LEDs. (A rep for Acuity declined to answer questions about the company’s LED suppliers.)
“I often find that companies don’t really know what they’re buying,” Pecht said. “They look at prices. It’s really a supply chain management issue.”
This is one of the reasons why purple can make a big difference. This shows how deeply LEDs, especially cheap white LEDs, are intertwined with the global economy. Of course, Acuity may have fixed the problem and replaced all indicators. But what happens the next time a company in southern China solder something wrong and a wave of broken technology swept the world? This time it’s street lights, next time it could be phones, televisions, medical equipment.
Street lights are more than just street lights. During the second half of the 20th century, most cities installed lights simply to keep the streets and highways as light as possible for cars. LEDs give them a new level of control. They can make street lights bright enough to match the road, fine-tune sidewalk shading, and create sleek computer-controlled components that brightly illuminate building facades without making people’s apartment interiors look like the Las Vegas Strip.
This is where emotional and aesthetic elements come into play. In terms of appearance, there is no objective difference between an orange sodium lamp and a white LED, unless you are very concerned about colorimetry. But when that orange glow defines your city and your childhood—as it did for a Los Angeles or Chicago resident like me—you don’t take any change lightly. The night lights make the city a completely new place, “a luminous and reflective structure, no longer dependent on the geometric and material resolution of the day,” as Isenstadt once wrote. Night illumination of the place literally defines its outlines. The new color refreshes everything.
LEDs give us new ways to use colors and ways to reimagine the urban sky. A city is a city, and their decisions are largely based on cost – typically 4000k in cool blues and whites. It was a conscious, informed choice. But now, due to the vagaries of world trade, the night colors of many cities suddenly change. People feel like something personal, something that defines their city, has been taken away. So they are looking for intent. Maybe for the holidays? Maybe it’s a conspiracy? It must mean something. Because if it’s not, it’s even scarier. Street lights and street lighting are the deep infrastructure of the city. If they can break in in such a strange and unexpected way, then so can everything else.

Post time: Dec-08-2022