Diane Turnshek grew up with the dark. She spent her childhood in New England camping and hiking, the night sky unfurled overhead in a familiar tapestry. During graduate school at the University of Arizona in Tucson, a city bordered by some of the darkest areas of the country, she spent plenty of time out in the desert, making observations of celestial bodies for her astronomy program. Then Turnshek moved to Pittsburgh, where she started teaching, first at the University of Pittsburgh and then at Carnegie Mellon University, where she still works. She had four children; and suddenly, driving hours outside of the city to view the night sky became a rarer and rarer occurrence until she could hardly recall what it looked like.
It was only in 2012, when she traveled to Bryce Canyon, Utah, to be a crew member of the Mars Desert Research Station, that she reencountered the enduring nighttime. “I hadn’t seen a dark sky like that for decades. It hadn’t dawned on me in the intervening years that there were no more stars — not on the East Coast. And that’s really when I started campaigning for people to notice that there’s light pollution and to try to do something about it,” Turnshek said.
Due to increased artificial light use at night, we are rapidly catapulting toward a future in which nearly all people in industrialized countries will never see the Milky Way, or the great majority of stars, for the whole of their lives. The effects of this deprivation are hard to comprehend. On one level, we have plenty of evidence about what we physically lose when we over-light the night; a good night’s sleep is the most obvious and well-evidenced response. So too are the myriad detrimental effects on bird migration, nocturnal animals, even trees. But we may be losing something more intangible: the ability to see the universe and to glimpse our place within it. Since joining Carnegie Mellon University’s faculty in 2008, Turnshek says she’s gradually noticed a shift in her students: more and more of them have never seen an undiluted night sky. “They have this esoteric understanding that there’s other things out there, but it’s like they’re on the other side of a door. They can’t see them.”
Kicking down that door and creating dark sky-friendly cities is the implausible dream of Turnshek and her colleagues. Audrey Fischer, a former International Dark-Sky Association (IDA) board member, says that a common assumption among residents in her native Chicago is that “it’s impossible to have starlight over a city and to try to go after that goal is a waste of time and energy.” That hasn’t stopped IDA chapters from sprouting in some of the country’s largest cities, including New York City and Washington, DC.
The IDA was founded in 1988 “to preserve and protect the nighttime environment and our heritage of dark skies through environmentally responsible outdoor lighting.” Many of the city-based groups have mobilized around the issue of streetlights — specifically, the large streetlight replacement programs that are converting all metal halide, mercury vapor, and high-pressure sodium luminaires to light-emitting diodes (LEDs). But not all LEDs are created equal. To the dismay of dark-sky activists and some city residents, many cities installed ultra-bright LEDs that emit a blue wavelength similar to that of the daytime sky. Selecting warmer colors of LEDs would help the stars shine through, but groups like the IDA would also like to see streetlights that are shielded and dimmable and backed up by a robust city lighting ordinance.
A few years after her stint at the Mars Desert Research Station, Turnshek founded a local chapter of the IDA in Pittsburgh. They had their first meeting in 2017. The group immediately turned its sights to the city’s streetlighting. Pittsburgh officials have been discussing replacing all 40,000 of the city’s streetlights for the past decade, and Turnshek and the other IDA Pittsburgh members want to ensure that the replacement lights are as minimally intrusive as possible, while still maintaining safety and visibility.
But first, they needed to understand the scope of the problem. To this end, Turnshek, her CMU colleague Stephen Quick, and members of IDA Pittsburgh are developing a comprehensive light pollution map of the city — all 58 square miles. Unlike other maps, theirs will take measures of light pollution from above looking down using drones and a camera-equipped Cessna aircraft and from below looking up using human volunteers armed with spectrometers. This work has largely been halted since the coronavirus pandemic started, but they hope to restart when it is safe to do so. In addition, the map will also account for light pollution readings from satellite data to create an overarching measure of light pollution in the city. There is no light pollution map currently available that encompasses all of these measurements. Turnshek and Quick are also planning on making a second map after the LEDs are installed; together, the two maps will provide a concrete measure of how levels of light pollution are impacted by LED adoption and will highlight the city’s biggest light pollution offenders.
Turnshek sees the forthcoming streetlight conversion as an opportunity to transform Pittsburgh into a model for responsible streetlighting. “Pittsburgh, to me, is like the proving ground for the world,” she said. And if city officials choose lighting that adheres to IDA recommendations, it’s the first step toward making Pittsburgh the East Coast’s first dark sky city. But can it be done?
In 2011, Pittsburgh received a grant from the state to install more than 3,500 LED luminaires as part of an early pilot program. Compared to the high-pressure sodium (HPS) fixtures you’d find illuminating a typical American street with their characteristic deep yellow glow, LEDs are more cost-effective and energy-efficient. Speaking to Pittsburgh’s local NPR affiliate, Alex Pazuchanics, former assistant director in the Department of Mobility and Infrastructure, estimated that LED streetlights could lower the city’s energy bill by up to 70 percent.
Many environmental groups have welcomed the changes. LEDs are far more energy-efficient than their predecessors. Given that nearly 20 percent of the world’s overall energy consumption is consumed by lighting, some see the transition to LEDs as a welcome opportunity to reduce greenhouse gas emissions.
The people who actually have to live with the lights are less enthusiastic. Pressured to cut costs, many cities installed an early generation of high-intensity, blue-rich LEDs, notorious for producing lots of glare. In Davis, California, residents objected so strongly to the new lighting that the city spent an additional $350,000 to replace the newly installed bulbs. A similar story unfolded in New York City in 2016. One Brooklyn resident wrote in an online petition that the new streetlights cast “an eerie day-for-night glow, like a Walmart parking lot or a zombie picnic.”
Pittsburgh officials asked researchers at CMU’s Remaking Cities Institute to observe the installations in 2010; Quick was a research associate on the project. The new LEDs were centered mainly in the city’s business districts, commercial areas, and major roadways. Five years later, Quick’s team conducted another study on streetlighting. They found that all the LED lights they tested produced significant glare problems.
“People think that by making light at night equivalent to daylight that that’s the best solution. But trying to simulate daylight is a real problem.” Quick said. His team found that once people’s eyes adjust to the dark, it’s difficult to shift back and forth between darkness and simulated daylight. Our capacity to transition quickly in and out of night vision degrades as we get older, along with our reaction time. So, for example, reacting to a potential hazard on a dark street right after turning off a heavily lit freeway becomes more difficult with age. “If you could design a light for a 65- to 70-year-old person, to meet their reaction times, you would end up with a Dark Sky compliant fixture,” he said.
Their findings track with other research on blue-rich LEDs. The color temperature of many of those first-generation LEDs was around 4,000K — squarely in the blue end of the spectrum. A 2016 American Medical Association (AMA) report found that widespread installation of this type of LED streetlight is associated with “significant human and environmental concerns,” including disrupting our sleep and diverting the behavior of light-attracted animals, like pollinating moths and sea turtle hatchlings. The report emphasized that one of the main disadvantages of LED technology is the color temperature of the lights, which are measured in Kelvin. Higher-Kelvin lights emit light at a shorter wavelength. Daylight, for example, has a color temperature of 6,500K (which is why the sky is blue); on the other end of the spectrum, a flickering candle measures at 1,800K (which is why it looks yellow). Blue light has one more disadvantage: it scatters more easily than other temperatures, creating an even brighter sky glow over cities.
Both the AMA and the IDA recommend fixtures with color temperatures no higher than 3,000K. “The lower Kelvin lights are cost and energy efficient, safer, better for human health and wildlife conservation, and contribute less to skyglow,” states the IDA’s website. But it’s not just color temperature that matters: the AMA and the IDA also recommend lights that are dimmable and shielded so that the light points downward.
Even since the publication of the second report, Quick said they’ve seen significant technological improvements in LED lighting. “At the time we started our first study, streetlights were not a very popular item for manufacturers,” he says. “They’re not a high-profit item. Part of our report was to say, you have to start thinking about the quality of light – glare issues, contrast.”
In 2018, the city of Pittsburgh put out a request for proposals for a smart LED streetlight system. But when it got to the point of negotiating with potential vendors, city officials realized they were lacking key information to meaningfully enact the transition. “We really just didn’t have the data that was necessary to make good decisions around that program,” Karina Ricks, director of the Department of Mobility and Infrastructure, said. “We got too far out over our skis.” Ricks explained that the city doesn’t even know exactly how many streetlights they have or how many of them have already been converted to LED. “When this all became quite apparent to us, that we were missing the initial data to make the most of such a program, we pulled back that solicitation,” Ricks said.
Luckily, Pittsburgh’s relative cautiousness in replacing the remainder of its streetlights means that it can now choose streetlighting that’s more friendly to the human eye. Although the exact type of lighting that will be installed is not yet known, the LED lighting market has evolved over the past few years such that lower-color temperature LEDs are now available to purchase at a commercial scale. And because LEDs can last 15–20 years, greater diligence upfront has potentially saved the city from ending up like Davis. A “dark sky city” is a misnomer: should Pittsburgh become dark sky certified by the IDA, that doesn’t mean the city itself will be completely dark at night. But it does mean that light-polluted area around the city will shrink. Instead of having to drive 45 minutes outside of the city to see the Milky Way, you might only need to drive 20 minutes.
Humans remain keenly aware of associations between lighting and safety, and urban dwellers, who are more likely to walk, cycle, or use public transportation, may be particularly sensitive to streetlighting. All of the IDA activists interviewed for this article said that one of the most recurring concerns they encounter when speaking with people about reduced nighttime lighting is the possibility of increased crime. Nick Mullen, a 24-year old Pittsburgh resident, said in an interview that he preferred bright white LEDs because they made him feel safer walking around his neighborhood at night.
“We’re looking for a balance between safety on the ground and dark skies at night,” Quick said.
Finding that balance is still very difficult. John Barentine, director of public policy at IDA, says that the research on lighting and crime has produced mixed results. “How much of the lighting and crime situation is about perception and feeling and not about actual evidence that the light is doing one thing or another?” he asked. “We just do not know the answer to that question to be quite honest.”
A recent working paper shared by the National Bureau of Economic Research is an evocative step toward one. Researchers, in partnership with New York City agencies, conducted the first randomized field experiment studying the relationship between outdoor lighting and crime. At the end of their six-month study period, they found that increased lighting resulted in a reduction of crime by at least 36 percent. But given that only 12 percent of crimes in their study took place outdoors and at night, the adjusted result is a 4 percent decrease. The paper’s authors note that the temporary lighting towers were extremely bright, intensely focused, and a prominent, short-term intervention in the neighborhood — all factors that might not make them a realistic solution in the long-run or appropriate for many neighborhoods.
But for many residents, even an increase in the perception of safety due to brighter streetlights can result in positive community changes. “I used to be afraid to go out at night with my kids,” said Queens resident Stephanie Arias, speaking to The New York Times on the bright LEDs installed in her neighborhood in 2015. “There are a lot of stupid little guys around who like to start stuff. Now it’s different.” According to Ricks, light equity is a major piece of the forthcoming streetlight conversion in Pittsburgh, even if it means a reduction in potential energy savings. Remedying unequal lighting may mean more lights in certain areas of the city, Ricks said.
Some have been critical of light-based social interventions, noting that it is predominantly working-class Black and Latino neighborhoods that are subject to excess artificial light at night. Speaking to The Atlantic in 2013, author Paul Bogard refers to groups such as public housing residents, night-shift workers, and incarcerated people as “darkness-deprived populations.”
“It’s like so many of these other things — green space, trees, quiet, and so on,” Bogard says. “It could end up being unevenly distributed; where the only way to get real darkness is to be able to afford to live in a community like Aspen or Vail or somewhere like that.”
Light is a profoundly ambivalent resource, and dark sky activists wrestle with the myriad ways that nighttime lighting supports (or curtails) safety, equality, and community. But that’s why they believe the central question is not if, but how, we should use lights at night. In a world of stark contrasts, dark sky activists argue that by carefully attending to our surroundings, we can create a more equitable nighttime, and with it, a more thoughtful and deliberate approach to both the community — and galaxy — outside our front doors.
Lights in public places, like streetlights, play a major part in decreasing humanity’s light footprint, but dark sky activists would like to see even more action from their local governments going forward. The advent of “smart” lighting solutions, which equip LED streetlight fixtures with sensors and connect them to a central management server, makes the goal of a darker city arguably more achievable than ever before. Pittsburgh is still considering which sensors to include in any streetlight upgrade, Ricks said. But the potential for downstream effects on light pollution are myriad. Consider, for example, a sensor that allows cities to monitor pedestrian levels and dynamically adjust lighting accordingly, or automatically dim streetlights between certain hours.
In the coming months, Turnshek says the way forward will include more policy advocacy — specifically amending the city’s lighting ordinance policy, in addition to completing the light pollution map. The ongoing COVID-19 pandemic has added complications to both goals, slowing down policymaking and causing light pollution to fluctuate. Widespread shuttering of commercial and industrial areas has caused both air and light pollution to plummet. Turnshek said that people are scrambling to take sky glow measurements to give this darkness a number.
Even with a pandemic raging, Turnshek and Quick are still forging ahead, preparing a second grant application to Metro21: Smart Cities Institute, an interdisciplinary research institute at CMU, to potentially fund future town hall meetings, public service announcements, and community campaigns for an amended outdoor lighting policy. They remain focused on building a darker, clearer future, where stars will shine over Pittsburgh once again.