Years ago, I called the local electric and streetlight utility, Seattle City Light, to ask why the block around the corner was lit up like a sleep-deprivation torture cell. Then as now, seven high-powered LED lights, plus two on facing corners, blazed away—more than twice the usual allotment in this hilltop neighborhood of close-packed bungalows less than three miles from downtown Seattle.
“That’s because it’s a high-crime block,” the guy I reached told me.
How do you know that? I asked.
“Because it has so many lights.”
I asked for more data, but he didn’t have any.
From the July/August 2011 issue: The light fantastic
He surely didn’t realize that less than 200 feet away was another block with no streetlights at all—one of 16 blocks within half a mile that missed out on, or escaped, the street lighting considered obligatory elsewhere. When the blocks were developed, in the early 1900s, a resident told me, the builders opted to hide the utility wires that ordinarily clutter urban streets by running them down the alleys. So the city, which makes utility poles do double duty as streetlight bases, set lights midblock in the alleys, but not on the streets.
The result is one of Seattle’s best-kept secrets. When I asked City Light’s longtime public-affairs chief if there were any other unlit streets in the city, he insisted that there were none anywhere, not even in these 16 blocks. He then called back, after checking, to correct that.
Freed from ugly wires and nighttime glare, many of the unlit blocks are strikingly beautiful. Elsewhere, old trees are cropped into scraggly U’s to accommodate the wires; here they grow freely, forming green arches over the dark streets.
These blocks offer an urban refuge, and something else: a natural experiment.
The idea that street lighting—the more the better—prevents crime is so embedded in our culture that tautologies like because it has more lights come easily. This assumption persists against the objections of scientists, stargazers, and organizations such as DarkSky International. And it persists despite mounting evidence of the baleful effects of excessive and misdirected illumination—a.k.a. light pollution—on wildlife and human health, not to mention on the sense of wonder of people who grow up never seeing the Milky Way.
Even some politicians and police officials have come to question the dogma. Art Hushen, formerly with the Tampa Police Department, is one such cop; he now teaches cities and police departments around the country how to light less and light smarter. “You get communities saying, We need more lights,” he told me. “No, you don’t. You need better lights.” And better lighting doesn’t mean brighter lighting.
Over the years, a number of cities have experimented with their streetlights, sometimes turning them up and sometimes dimming them. The results have been contradictory; officials and researchers alike have come to varying conclusions.
In 1998, Chicago adopted an initiative called the Chicago Alley Lighting Project. It replaced 90-watt bulbs with 250-watt fixtures, then had the Illinois Criminal Justice Information Authority gauge the results in two sample areas. It found more reported crime in the year after installation than the year before, with especially “notable increases” in the first six months.
The evaluators speculated that this reflected not so much a change in underlying crime rates as an increase in visibility: Residents who “may have not taken notice of drug activity before” were now more likely to report it.
Edward Bartholomew, a lighting designer and co-founder of the advocacy group Light Justice, suggested another possible explanation: Overlighting can assist criminals. “ATMs are the classic case. Bright lighting puts people on stage to get robbed.” Elsewhere, glare-struck victims may not see threats lurking in the shadows cast by floodlights. I once asked a builder why he left the lights off in the houses he was working on. “Lights just help the thieves find their way.”
In 2002, the city of Calgary, Alberta, dimmed the lights on residential and arterial streets, replacing 150- and 250-watt bulbs with 100- and 150-watt ones and switching from glare-scattering drop lights to flat lenses that cast light toward the ground rather than to the sides and into people’s eyes.
When I wrote about this “EnviroSmart Streetlight Retrofit Project” for the magazine Discover in 2003, Calgary’s streetlight coordinator, Barry Poon, told me that before the changeover, citizens, especially elderly ones, warned that it would boost crime. “But police told us there’s no correlation between light levels and crime,” Poon recalled. “Breaking-and-enterings actually occur in daytime when people aren’t in.” The results confirmed this: Calgary’s crime rates were unchanged. Post-changeover, Poon told me, “I’d say we get 10 positive responses for every negative one”—plus the $4.5 million retrofit enables $1.3 million a year in electricity savings.
Municipalities across England and Wales provided an even broader natural experiment. In the early 2000s, high electricity costs and growing climate concerns prompted many of them to dim their streetlights, turn them off late at night, or shut some off permanently. Researchers funded by Britain’s National Institute of Health Research compared collision and crime stats before and after the changes in 62 local jurisdictions. Their findings, published in the British Journal of Epidemiology and Community Health, were surprising. Local results varied, but on average the researchers found “no evidence” of any change in crime rates after streetlights were switched off entirely or for part of the night. They did find “weak evidence” that crime rates declined when streetlights were dimmed, and when localities switched from yellowish high-pressure sodium streetlights to bright-white LEDs. None of these changes seemed to affect the number of roadway collisions.
That study’s takeaways: The benefits of streetlights are overrated. Brighter is not, on average, better. Dimmer may be.
In 2008, a meta-analysis of lighting studies in Britain and America from the 1970s, ’80s, and ’90s, by contrast, concluded that “improved street lighting significantly reduces crime.” But it suggested that this reduction might be due not to surveillance and deterrence but to increased “pride, community cohesiveness, and informal social control” engendered by the validation of public investment. It noted that a review and an evaluation by the British Home Office of improved street lighting found little or no effect.
One of the most high-profile—and brightest—lighting interventions was executed under New York City Mayor Bill de Blasio. The program “weaponizes light,” in the words of Light Justice, while also deploying a heavy, highly visible police presence, in a scheme to reduce crime in public-housing developments. In 2014, without consulting affected residents, his administration deployed an initial 150 floodlight towers powered by noisy, smelly diesel generators across 15 housing projects. Each tower cast 600,000 lumens (while ordinary streetlights cast about 3,000 to 15,000 lumens). The program received the ominous sobriquet “Omnipresence,” and the effect was overpowering—in some cases, bright “enough to light up a professional ballpark,” recalled Hushen.
It was also stunningly successful, according to a study of crime rates undertaken in 2016, at the city’s request, by the National Bureau of Economic Research. Forty more New York City Housing Authority projects received the floodlights; another 40 served as randomized controls. After accounting for “potential spatial spillovers” (that is, criminal activity moving outside the lit-up areas), the researchers found that outdoor nighttime “index crimes” (those included in the FBI’s crime index) fell 36 percent in the floodlit zones. A follow-up study conducted three years later found that these effects had persisted. The light towers were originally supposed to stay up just six months, the criminologist Aaron Chalfin, who led both studies, told me, but he said residents clamored to keep them, so they remained.
Bartholomew contended that residents supported the lights because they had no better options. “People who don’t have access to wealth and power and privilege don’t have access to good lighting. They don’t even know about it.”
As Batholomew also noted, the studies did not consider “secondary effects”: the health and psychological impacts of excessive nighttime lighting. Disrupted circadian rhythms and sleep deprivation have been linked to obesity and depression.
Hansen countered that “lower crime rates offer important health and mental benefits to consider as well,” and suggested that public housing could invest in better window shades. That, he said, was “a low-cost solution to weigh against the benefits of streetlights creating public safety.”
Regardless, lessons drawn from floodlighting public housing developments in one densely packed megacity may not be so relevant to ordinary residential streets. As Bartholomew put it, “I guarantee you, none of those researchers would want one of those floodlights in their front yard.”
All of these were longitudinal studies, comparing outcomes (crime rates) across time as conditions (street lighting) changed. It occurred to me that my neighborhood’s dark streets offered a rare opportunity to conduct an informal cross-sectional investigation of my own, comparing outcomes in different samples (in this case, lit and unlit streets) over the same period.
I tramped around at night identifying blocks without streetlights and, for comparison, similar nearby, often adjacent, blocks with lights. I then used a Seattle Police Department data set going back to 2008 to tally the crimes reported on each block that were likely to have occurred at the actual addresses, such as robbery, burglary, and car thefts. Granted my sample size was small, but there did not seem to be any dramatic difference in the data between dark blocks and similar blocks that had lighting. If anything, the lit blocks reported slightly more crimes.
As I scoped out those blocks, I asked residents I bumped into what living without streetlights was like and whether they thought it affected criminal activity. Some had a complaint—common in many Seattle neighborhoods—about petty crime, but no one tied it to the lack of lighting. Kristine and Michael Sendelbach, who live in a classic bungalow behind a luxuriant arching bower, were the most forthcoming. “It’s a nice atmosphere,” Michael said, and because it’s so pleasant, “this street gets a lot of foot traffic, people jogging and walking dogs”—the proverbial eyes on the street. In their 33 years there, the Sendelbachs had never suffered a break-in, though some neighbors had. Items such as phone chargers sometimes get “plundered” from unlocked cars, Kristine said, but the thieves seemed to be “people who are desperate, not organized theft rings,” and “it just feels like lights wouldn’t help.”
As Michael explained, “Most of the crime happens in the alley”—where the lights are.