Can Better Lighting Prevent Crime?

A place-based intervention core to urban crime prevention through environmental design is ample lighting. It can encourage pro-social use of neighborhood streets after dark, increasing informal guardianship, natural surveillance, and further disincentivizing potential offenders. 

A Philadelphia streetlight crime study, beginning in August 2023, observed that upgrading around one-third of city’s streetlights had an observable and statistical effect on crime citywide. The impact on nighttime outdoor crimes was pronounced, with an overall crime decline of 15%, a 21% drop in gun crimes, a 20% drop in violent crimes, and a 16% drop in property crimes. 

Philadelphia’s LED Streetlight Project Crime Results

The study, “Can Enhanced Street Lighting Improve Public Safety at Scale?” by John MacDonald, Aaron Chalfin, and additional researchers at the University of Pennsylvania supports the effectiveness of LED streetlights in crime prevention. Their study observed the first 10 months of streetlight upgrades citywide across Philadelphia, marking the outset of a two-year municipal safety plan to upgrade all of the city’s streetlights. During the study period, more than 34,000 streetlights across 13,000 street segments were upgraded. This study captured the impact of lighting improvements across a larger sample than prior studies.  

Bulbs were upgraded from existing yellow bulbs to LEDs. The new LED lights provide better quality lighting and more uniform coverage. LEDs use less energy but improve illumination. The LED system also automatically notifies city planners when a streetlight goes out rather than relying on 311 calls to the city. 

Many of the blocks upgraded were among Philadelphia’s poorest neighborhoods and had experienced disproportionately high crime. These neighborhoods experienced higher-than-average gun violence before the pandemic and bore the brunt of pandemic-era increases.  

Serious violent crime and gun crime are still extremely rare — even the most predisposed blocks experience only a few incidents every year. This study contributes to a body of research suggesting that specific features of the built and social environment play a role in crime opportunities and that small changes can have a meaningful impact on crime victimization.  

Most studies into the impact of improved lighting on property and violent crime in cities have focused on a small number of discrete locations. This new study is noteworthy because it occurred at scale. Additionally, many street lighting studies predate the widespread use of technologies like CCTV and smartphones. It is worth noting that these technologies have altered use and guardianship across public places. 

Crime Mapping and Streetlight Data 

Another body of work involving street lighting took place between 2000 and 2020, during a period of overall reductions in crime, meaning the efficacy of streetlights as a crime deterrent has not been set against the circumstance of high or rising crime. The 2023 University of Pennsylvania study captures a period when local and national crime was on the rise, providing an opportunity for scaling street lighting as a public safety measure to demonstrate its effectiveness in a circumstance where crime is increasing. 

Philadelphia’s lighting upgrades were associated with a statistically significant reduction in overall crime, including gun crimes, violent crimes, and property crimes. In the plots below, the red line denotes the beginning of the streetlights upgrade project. 

The upgrades led to a 5% decrease in overall crime, a 4% decrease in violent crime, a 7% decrease, and a 17% decrease in gun crimes. The interventions produced a stronger effect when measured in percentages of outdoor crimes, a 19% decrease in gun crimes — an 11% decrease in violent crimes, and a 16% decrease in property crimes. The impacts were most strongly attenuated to nighttime outdoor crimes: with an overall crime decline of 15%, a 21% drop in gun crimes, a 20% drop in violent crimes, and a 16% drop in property crimes. An impact of street lighting was additionally observed reducing gun crimes that occurred inside. Unexpectedly, researchers captured a small 4% drop in crimes during the daytime hours. 

Public Safety Through Urban Design 

While some studies of small-scale lighting interventions have created additional questions about whether crime merely moves to poorly lit blocks, this study’s researchers found that upgraded streetlights also reduced crime on adjacent street segments.  

Researchers engaged in ethnographic observations and interviews with community members before and after the upgrades. Tours of streets before upgrades featured many areas of low light with inoperable or poorly functioning streetlights, leaving dark areas. Interviewees stated that many of these streetlights had been burnt out or malfunctioning for several weeks. The poor quality of light impacted community routines, with interview subjects stating they would alter routes to avoid blocks with inadequate lighting and tended to stay indoors after dark. Numerous respondents also stated they would leave the neighborhoods entirely to seek evening social functions. 

Interview subjects expressed doubts regarding the updated lighting’s ability to curb gun violence, citing instances of gun violence that had occurred in broad daylight. Streetlight upgrades on their own were not viewed as a critical anti-violence strategy. Yet after the lighting intervention, many residents reported feeling safer and expressed more confidence in using outside areas after dark. 

Philadelphia’s citywide streetlight upgrades show the promising capacity of place-based interventions to produce salient citywide crime prevention. Their project is projected to be completed by the end of 2025. 

While the fixed costs of upgrading light fixtures can be high, the associated maintenance costs are relatively low and may be lower than the costs associated with maintaining legacy lighting. Street lighting is a scalable policy that can be used to reduce crime, in line with other environmental interventions such as blight remediation, greening vacant lots, and bringing down abandoned buildings.  

The Pinkerton security consulting team is adept at helping our partner firms use site risk assessments as part of a broad toolkit to assess crime risk and understand how crime prevention through environmental design and other place-based strategies can meaningfully impact risk.