Reducing Crime Through Environmental Design: Evidence from a Randomized Experiment of Street Lighting in New York City
Last registered on May 13, 2019


Trial Information
General Information
Reducing Crime Through Environmental Design: Evidence from a Randomized Experiment of Street Lighting in New York City
Initial registration date
May 08, 2019
Last updated
May 13, 2019 11:49 PM EDT
Primary Investigator
University of Pennsylvania
Other Primary Investigator(s)
PI Affiliation
University of Chicago Crime Lab
PI Affiliation
University of Chicago Crime Lab
PI Affiliation
University of Oregon
Additional Trial Information
Start date
End date
Secondary IDs
This paper offers novel experimental evidence that crime can be successfully reduced by changing the situational environment that potential victims and offenders face. We focus on a ubiquitous but surprisingly understudied feature of the urban landscape --- street lighting --- and report the first experimental evidence on the effect of street lighting on crime. Through a unique public partnership in New York City, temporary street lights were randomly allocated to public housing developments. We find evidence that communities that were assigned more lighting experienced sizable reductions in nighttime outdoor crimes.
External Link(s)
Registration Citation
Chalfin, Aaron et al. 2019. "Reducing Crime Through Environmental Design: Evidence from a Randomized Experiment of Street Lighting in New York City." AEA RCT Registry. May 13.
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Experimental Details
The field experiment described in this paper was conducted in the Spring and Summer of 2016 in NYC. Through a unique partnership between NYPD and the NYC Mayor's Office of Crime Justice, we randomized the provision of temporary street lights to the city's public housing developments, allowing us to avoid the potential challenges that could result due to spurious time trends as well as selection bias. Managed by NYCHA, NYC's public housing developments are officially home to more than 400,000 New Yorkers (and perhaps an additional 100,000 non-official residents), making NYCHA the second largest landlord in the United States after the U.S. military. NYC's official public housing population is indeed large enough to place it among the forty largest cities in the United States, making it an ideal setting to study the effect of street lighting in urban areas.

Given the cost of providing enhanced street lighting at scale, the city wanted to launch a pilot study to investigate the extent to which increased lighting would be effective in reducing serious crime. We worked closely with the City for nearly two years to develop the field experiment described in this paper. The intervention deployed temporary lighting towers to housing developments across NYC. These towers emit approximately 600,000 lumens---a measure of brightness---making them extraordinarily luminous. Towers were equipped with an automatic timer set to switch on at sunset and off upon sunrise.
Intervention Start Date
Intervention End Date
Primary Outcomes
Primary Outcomes (end points)
Index crimes occurring outdoors at during the nighttime hours
Primary Outcomes (explanation)
Secondary Outcomes
Secondary Outcomes (end points)
Index crimes occurring outdoors at during the daytime hours
Secondary Outcomes (explanation)
Experimental Design
Experimental Design
In order to select developments for the study, the New York Police Department provided a list of 80 high-priority developments based upon their elevated crime rates and perceived need for additional lighting from among the 340 NYCHA developments in NYC. From this list, we randomized 40 developments into a treatment condition that would receive new lights and 40 developments into a control condition via paired random sampling, stratifying on each development's outdoor nighttime index crime rate and size in the two years prior to the intervention; treatment developments were then randomly assigned a lighting dosage.

In order to maximize statistical power, we also randomly assigned the dosage of lighting among the treatment group. Three hundred and ninety-seven lighting towers were available to be randomly assigned amongst the treatment group. For operational reasons, the City decided that two light towers would be allocated to each campus, regardless of square footage. The remaining 319 lighting towers were assigned to the 39 developments according to a random number drawn from a uniform distribution linked to the square footage of the developments. This created exogenous variation in the the number of lights per square feet across the developments.

Light towers were deployed in the field between February 29, 2016 and March 7, 2016; the lights remained illuminated during all nighttime hours for the following six months. Control group developments received no additional outdoor lighting ("business-as-usual").
Experimental Design Details
Randomization Method
Randomization was completed using the statistical software package, Stata.
Randomization Unit
The unit of randomization is the public housing community.
Was the treatment clustered?
Experiment Characteristics
Sample size: planned number of clusters
Sample size: planned number of observations
80 (for treatment vs. control analysis) 40 (for analysis of the effect of lighting dosage)
Sample size (or number of clusters) by treatment arms
2 (for treatment vs. control analysis)
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)
IRB Name
University of Chicago Social & Behavioral Sciences Institutional Review Board
IRB Approval Date
IRB Approval Number
Post Trial Information
Study Withdrawal
Is the intervention completed?
Is data collection complete?
Data Publication
Data Publication
Is public data available?
Program Files
Program Files
Reports and Papers
Preliminary Reports
Relevant Papers