Key takeaways
- 21% reduction in outdoor gun violence and 15% decrease in overall outdoor nighttime crimes in areas with upgraded LED street lighting
- No crime displacement: Crime actually decreased on adjacent streets by 3.25% due to spillover effects, rather than simply moving to nearby areas
- Residents saw lighting as community investment: Focus groups revealed that better lighting was viewed as a signal that neighborhoods matter, fostering hope that more people could safely be outside at night
- Largest study of its kind: First citywide-scale evaluation of street lighting in the U.S., examining 34,374 upgraded lights across 13,275 street segments over 10 months
- Lighting accounted for one-sixth of citywide gun violence decline: The intervention contributed approximately 5% of Philadelphia’s total 31% reduction in gun violence during the study period
This article is reprinted with permission from The Police Research Hub.
Your agency is expected to solve every crime problem in the city. More patrols. More programs. More resources. The pressure to design comprehensive interventions can be overwhelming.
But what if one of the most effective crime prevention strategies was already hanging above every street corner?
A groundbreaking study from Philadelphia shows that something as straightforward as upgrading street lights can drive measurable reductions in crime. This isn’t a pilot program in a single neighborhood. They show that this level of crime reduction can happen at scale, across an entire city.
The study: Lighting up an entire city
Researchers John M. MacDonald, Aaron Chalfin, Maya Moritz, Brian Wade, Alyssa K. Mendlein, Anthony A. Braga, and Eugenia South examined what happened during the first 10 months of Philadelphia’s citywide street lighting upgrade.
Between August 2023 and May 2024, the city replaced outdated high-pressure sodium (HPS) bulbs with LED lights on 34,374 streetlights across 13,275 street segments which is about 1/3 of Philadelphia.
The research team didn’t just analyze crime data. They spent hours observing neighborhoods before and after upgrades, conducted 19 in-depth interviews, and held four focus groups with residents in high-violence areas to understand how the changes affected community perceptions of safety.
This is the largest street lighting intervention ever studied in the United States. Previous research on street lighting and crime focused on parking lots or individual neighborhoods, typically finding crime reductions averaging 14% across studies. But those were smaller-scale interventions. This study answered a critical question: Can better lighting reduce crime when implemented across a large portion of the city?
The findings: Gun violence reduction
Let’s break down what the researchers found, and what it means in practical terms.
How they studied it
The researchers needed to prove that crime reductions were actually caused by the lighting upgrades, not by other factors like shifting police deployments or existing crime trends. To do this, they used a difference-in-differences design, which compares crime rates before and after the lighting changes in treated areas versus untreated areas. The statistical models controlled for pre-existing crime patterns in each hexagon and accounted for citywide trends over time.
The team ran multiple statistical models to make sure their findings were solid, accounting for different crime trends across Philadelphia’s four regions, controlling for each street segment’s unique crime patterns over time, and checking whether areas receiving lights earlier or later showed different results. Across all these different ways of analyzing the data, the results remained consistent: lighting upgrades reduced crime.
Overall crime reductions
- 15% decrease in outdoor nighttime crimes overall
- 21% reduction in outdoor gun violence
- 20% drop in outdoor violent crimes at night
- 16% decrease in outdoor property crimes at night
To put this in perspective: The statistical model found that each additional upgraded light reduced gun offenses by 0.00519 per month per kilometer. With an average of 11.14 lights installed per kilometer across the 627 upgraded hexagons, this translates to approximately 36 fewer gun crimes per month in the treated areas. The street lighting intervention accounted for approximately 5% of Philadelphia’s total citywide decline in gun violence, roughly 1/6 of the overall 31% reduction the city experienced during this period.
When the lights matter most
The impact was strongest during nighttime hours, defined as 30 minutes after sunset to 30 minutes before sunrise. Better lighting shifts the risk-reward equation for potential offenders who rely on darkness to conceal their actions. Gun crimes dropped by 20% at night compared to a 4% reduction during daylight hours. The fact that there were also reductions during the day is noteworthy. It suggests the lighting improvements may have broader effects on the neighborhood environment beyond just nighttime visibility.
No crime displacement
One of the biggest concerns with any place-based intervention is displacement. Does crime just move around the corner? The answer here was no. In fact, the study found the opposite: crime actually decreased on adjacent streets by about 3.25% due to spillover effects from nearby upgraded lighting.
The cost-benefit
Philadelphia’s full citywide lighting upgrade will cost $91 million to replace all 134,550 streetlights. However, this study examined only the first 34,374 lights upgraded during the initial 10-month rollout.
The researchers calculated that the crime reductions generated a social benefit of approximately $697 per month per kilometer in the treated areas. Across the 627 hexagons (each 1 kilometer wide) that received lighting upgrades during the study period, this translates to roughly $437,000 in monthly social benefits or about $5.2 million annually from just this first phase of the rollout. This does not include the additional energy saving benefits provided by LEDs.
Why it works
Crime opportunity theory tells us that small changes to physical environments can have outsized impacts on criminal behavior. We’ve seen this with greening vacant lots, removing trash, and remediating blighted properties, all of which have shown measurable reductions in violence.
Street lighting works through multiple mechanisms:
- Increased visibility helps potential victims protect themselves and makes offenders more aware that witnesses or police might be present
- Reduced fear encourages more residents to be outside at night, which increases natural surveillance and community cohesion
- Deterrence removes the cover of darkness that offenders use to conceal weapons, illegal activities, and their identities
- Community investment signals that show residents their neighborhood matters, which can strengthen community bonds and encourage residents to look out for one another
What residents said
Before the upgrades, residents described streets with broken, flickering, or non-functioning lights that had been dark for weeks. Many had simply accepted that poor lighting was permanent. They avoided going out after dark and stuck to streets where lights still worked.
After the upgrades, the difference was stark. One resident captured the broader impact: “I think it would definitely send a message to the community that whoever is upgrading the street lights actually cares…they care about jobs…about our community…and about our welfare and our well-being. I think it would also foster maybe a beginning or a starting point of people being able to feel just a little bit more comfortable outside during nighttime hours, so eventually we could get to that point, one day, where a lot more people could be outside during the nighttime hours if they wanted to and not just have to stay stayed locked in their homes just because they’re scared.”
Residents viewed better lighting as essential for nighttime safety, but they were also clear-eyed about its limitations. Many emphasized that lighting alone wouldn’t solve deeper structural issues like poverty, failing schools, and lack of economic opportunity. As one participant put it, shootings happen in broad daylight too. Lighting is necessary, but it’s not sufficient.
How your agency can take action
1. Assess your current street lighting
Work with your city’s public works or utilities department to identify:
- Streets with high crime rates, especially at night, and poor lighting
- Areas with frequent reports of non-functioning lights
- Neighborhoods where residents report feeling unsafe at night
2. Build the case and engage leadership
This study gives you the evidence base you need. Bring this research to city councils, budget committees, and elected officials. Lighting upgrades are tangible, visible improvements that benefit everyone with constituents that see the change immediately.
When presenting, emphasize:
- Cost-benefit: Crime reductions that pay for themselves through reduced social costs and energy savings
- Spillover effects: Upgraded lighting benefits adjacent areas, not just treated streets
- Dual benefits: Reduced crime AND lower energy costs with LED technology
- Community investment: A visible signal that historically under-resourced neighborhoods matter, which can strengthen community bonds and encourage residents to look out for one another
- Quality of life: Immediate, measurable improvements residents can see and feel
3. Study and evaluate
If your city is planning lighting upgrades:
- Partner with a local university or research institution
- Track crime data before and after installation
- Survey residents about perceptions of safety
- Document the process for replication
4. Engage your community
Resident buy-in matters. Use community meetings to:
- Ask residents where lighting is poorest
- Explain the connection between lighting and safety
- Involve neighborhoods in identifying priority areas
This gives residents a stake in the intervention and reinforces the message that their community matters.
Final thoughts
Law enforcement is often asked to solve complex social problems with limited tools. But sometimes, the most effective interventions aren’t the most complicated.
Philadelphia’s experience shows that environmental design matters. Street lighting is a public health approach to crime prevention. ne that works with the community, not just in it. It doesn’t require hiring more officers. It doesn’t require new technology platforms. It requires treating the physical environment as part of your crime reduction strategy.
Better lighting won’t solve poverty, trauma, or systemic inequality. But it can make people safer. It can reduce fear. It can signal to residents that their community is worth investing in. And it can prevent real violence from happening.
Sometimes the most effective interventions are the ones already within reach. Street lighting is one of them.
Get more research from Carlee Ruiz translated into plain language delivered straight to your inbox. Subscribe here.
| WATCH: From research to roll call: Testing hotspot policing in the real world
