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Cleaning Up Vacant Lots Can Curb Urban Crime

Cities Infrastructure & Transportation

Crime Prevention Through Environmental Design

Editor's note: The following is the first article in the Urban Policy 2019 published by the Manhattan Institute.

Scholars who study urban problems are well aware of the powerful role that “place” has in shaping crime; they understand that the two are tightly coupled.[1] In the 19th century, André-Michel Guerry and Adolphe Quetelet found that crime in France was concentrated in the same places, and remained remarkably stable in those same areas, year after year.A century later, University of Chicago sociologists Clifford Shaw and Henry McKay noted that the crime was highly concentrated by place in Boston, Chicago, Cincinnati, Cleveland, Philadelphia, and Richmond, Virginia.[2] Even today, we continue to see a small number of particular locations in every major city generate the majority of serious crime.[3]

Hebrew University criminologist David Weisburd has referred to this empirical reality as the “law of crime concentration.”[4] In Philadelphia, for example, 5% of addresses where a crime was reported from January 2006 to December 2017 accounted for 50% of all crime in the city.[5] Given this reality, it makes sense to think about what changes we can make to curb these pockets of crime that exist in every major city.

The concentration of poverty, dilapidated homes, and vacant and abandoned spaces is endemic in urban pockets of crime.[6] Targeted community economic development would seem to be a natural solution. But there are few examples of policies that cities can enact in the short term to reduce poverty and decades of neglect in certain neighborhoods or communities, while at the same time protecting against sudden out-migration by long-term and multigenerational residents. In fact, the history of place-based economic development is not entirely encouraging. Harvard economist Edward Glaeser notes that state and federally funded urban economic development initiatives that target places have generally failed to generate benefits that exceed their costs.[7]

By contrast, cities can abate vacant lots and abandoned spaces and address proximal causes for why crime centers in specific places. Focusing on abatement also avoids the “causal fallacy” problem[8] of thinking that the only way to reduce crime is by addressing “root causes” like poverty. Evidence from social science suggests that patterns of crime change in step with the human-built environment, where higher crime areas devolve from single-family and multi-unit dwellings into places of blight and abandonment.[9] This spiral of decay is often just that: a process that feeds upon itself—from crime to abandonment to more crime, and so on. When people abandon a home or business, trash accumulates, graffiti multiplies, properties turn to ruin, and crime and disorder fester, triggering a cycle in which more people abandon their homes and businesses.

Crime prevention through environmental design and situational crime-prevention theories explain why vacant and abandoned spaces invite crime.[10] Poor visibility on streets attracts criminal offenders.[11] Overgrown shrubs, weeds, and trees on abandoned properties and vacant lots reduce the visibility of criminal activities on the streets[12] and discourage residents from walking down them.[13] Motivated offenders notice that they can avoid detection from bystanders and apprehension by the police when there are easy places to hide, and hiding makes it easier to surprise a potential victim. Wilson and Kelling’s “broken windows” theory also explains that signs of blight and disorder signal that an area is “fair game … for fun and plunder.”[14] Visible signs of disorder signal that no one cares and that community norms around civility are no longer obligatory. Physical signs of disorder like trash on the streets and abandoned and unkempt properties spread fear, lead to more abandonment, and signal to criminals that crime goes unabated. Decisions about how and where cities invest resources in the abatement of vacant lots could have a greater influence on reducing crime than many realize.

John Snow’s work on the causes of cholera in contaminated drinking water in the United Kingdom in the 19th century provides a historical example of how changes to a place can be transformative. Snow mapped cholera deaths in the Soho section of Westminster and showed that they clustered around the Broad Street water pump. After he petitioned local politicians to remove the handle of the water pump, cholera deaths waned. The simple act of removing a source of the epidemic vastly improved the health of an entire community and prevented cholera from reemerging in Soho.[15]

Philadelphia LandCare (PLC): A Case Study

Today’s cities can curb the incidence of crime by abating blighted vacant land. The benefits are clear, and a useful strategy is to give priority to programs that are simple to implement, are scalable to large populations, and are not expensive to sustain.[16] While addressing blighted vacant land has been advocated as a crime-prevention policy for decades, there are now examples of successful programs that cities can inexpensively replicate to reduce crime and encourage residents to remain in their neighborhoods for decades to come.

Philadelphia is one such example. Vacant and abandoned urban spaces are an effect of the 1960s and 1970s shift from an industrial to a service-based economy, the movement of people to the suburbs, rising crime, urban riots, and “block-busting” all of which led to the spiral of urban decay.[17] Cities such as Boston, New York, San Francisco, and Seattle have been able to successfully rebound from the deindustrialization of the U.S. economy by attracting technology and finance industries. But Philadelphia, like Baltimore, Cleveland, and St. Louis, has a legacy of blight and abandonment that had come to full scale by the 1990s.

In the later years of that decade, residents of the Kensington neighborhood in Philadelphia grew tired of the eyesore of vacant lots, the drug dealing, and other vices taking place in these areas around their homes. They teamed up with the Pennsylvania Horticultural Society and created a revitalization effort called “land and care,” now referred to as the Philadelphia LandCare (PLC) program.

PLC is simple and was designed to be applied across the neighborhood. Trash and debris are removed from a vacant lot. The land is then graded, and grass and a few trees are planted. A low wooden post-and-rail fence is installed with openings to permit residents access to the newly greened spaces. The fence prevents illegal dumping of garbage and construction debris; it is also a visual sign that someone is maintaining the property. The result is a small “pocket park.” The rehabilitation of such lots takes less than a week to clean and green. The lots are maintained through twice-monthly cleaning, weeding, and mowing during the growing season (April through October). The cost to clean and green a typical lot is roughly $1,000–$1,300, along with $150 per year to stabilize the lot through biweekly cleaning and mowing.[18]

Since its inception in 1996, the Kensington neighborhood’s PLC program has expanded through partnerships with local contractors and city agencies to the entire city, transforming more than 12,000 vacant lots and over 18 million square feet of land. Funds to support PLC are made possible by local community groups, the city, and private philanthropy. Philadelphia’s Department of License and Inspection (L&I) provides the legal mechanism for the PLC cleaning and greening abatement. Once a property is deemed to be in violation of city ordinances about vacancy, L&I contacts the owner of record. If the owner does not respond, L&I affords PLC the right to enter the property and green the vacant lot.

PLC cleaning and greening offers a unique opportunity to document what happens when abandoned and overgrown lots are rehabilitated. In our first study, we examined the effect of PLC remediation on crime between 1999 and 2008. In these years, PLC cleaned and greened roughly 8% of Philadelphia’s vacant lots (nearly 7.8 million square feet). We compared changes in crime around cleaned and green PLC lots with those of nearby vacant lots that remained blighted and were otherwise similar (e.g., lots with similar square footage, age of abandonment, and in neighborhoods with similar economic conditions). We found that crime had dropped by a statistically significant amount after the PLC cleaning and greening. In particular, assaults and assaults with guns dropped by a statistically significant amount (decreases of about 4% and 9%) around vacant lots after they had been remediated.[19] We did our best to address selection effects in this study, or the concern that PLC may have selected vacant lots to remediate that were somehow different from lots that remained blighted.

To provide stronger evidence that the PLC program was truly effective at reducing crime, we conducted a citywide, controlled experiment of the cleaning and greening program. With research funding provided by the National Institutes of Health and the Centers for Disease Control, we randomly assigned more than 500 blighted vacant lots to either receive PLC cleaning, greening, and maintenance or to remain in the usual state of blight. We found a significant reduction in crime around PLC-treated lots relative to lots that remained blighted. In particular, we found significant reductions in shootings (8%), assaults with guns (4.5%), and nuisance crimes (7%) such as public drinking and illegal dumping. The effects were even larger for neighborhoods below the poverty line, with the PLC treatment leading to a 29% reduction in gun assaults and a 28% reduction in nuisance crimes.[20] This evidence was consistent with our earlier study but is more convincing because the experiment ensured that treated lots were identical to the lots that remained blighted, controlling for anything we could measure that existed beforehand (e.g., crime and unemployment nearby).

A survey of residents living in the areas that were part of the experiment showed that those living near greened and cleaned lots reported significantly fewer concerns about their personal safety and an increase in the use of outside space for relaxing and socializing, compared with residents living near lots that remained blighted. Collaborators of ours, who inspected hundreds of PLC-remediated lots, noted the presence of tables and chairs, gardens, barbeques, and swings.[21] The PLC program provides clear evidence that remediating vacant lots reduces crime and improves what NYU sociologist Eric Klinenberg calls the “social infrastructure”: basic needs inherent in all city neighborhoods.[22]

If remediating vacant lots simply displaced crime to nearby places, there would be no citywide benefit. When we examined areas at farther distances from the vacant lots that had been cleaned and greened, we did not see evidence of rising crime. This was not surprising, as a review of studies of place-based interventions finds that they are about as likely to find a diffusion of crime reductions to nearby places, as they are to find displacement.[23] The opportunity to engage in crime facilitated by vacant lots may not easily be transferred to nearby places after lots have been cleaned and greened.

Beyond the reduction of crime and fear, the PLC program provides economic opportunities. PLC relies on a network of 18 community organizations that hire local landscape contractors to perform the work; these contractors hire individuals from the same communities to clean, green, and maintain the properties. As it has grown from a pilot project in the Kensington neighborhood to a citywide effort, the program has brought jobs and future career opportunities in landscape management to individuals in some of Philadelphia’s most economically disadvantaged communities. This has helped PLC expand to every area in need in Philadelphia, and it allows the resources devoted to vacant-lot abatement and maintenance to be spent in the affected communities.

To remediate the remaining 30,000 vacant lots in Philadelphia would cost $34–$45 million and about $5 million to maintain. The money spent doing the work would stay in the community, employing individuals with a decent wage and a semiskilled occupation that can spur economic self-sufficiency and entrepreneurship. The economic benefits of reduced crime are also clear. The results from our research imply that one can invest about $15,000 in the PLC program to avert a shooting. Our overall calculations suggest that $1 invested in the PLC program returns $26 in net benefits to taxpayers from reductions in gun violence, and as much as $333 in general costs to society, such as pain and suffering costs associated with a gun assault.[24]

Remediation Spreads

Programs similar to PLC are underway in Youngstown, Ohio, and Flint, Michigan, and are now being launched in New Orleans and Chicago. In Youngstown, a city that has experienced a 30% population loss between 1990 and 2010 and has a notable number of abandoned spaces, local residents and community groups apply to the Youngstown Neighborhood Development Corporation (YNDC) to remediate vacant lots. The applicants determine the type of remediation—typically, community gardens, but also urban farms or orchards, native plantings, athletic fields, and green spaces. Applicants who receive the funds are responsible for the upkeep. Results from an evaluation of nearly 250 vacant lots in Youngstown that were remediated compared with nearly a thousand vacant lots (in similar “neighborhoods” that remained blighted) found that the program reduced violent and property crime offenses in the nearby areas.[25]

In Flint, the local land bank, Genesee County Land Bank Authority (Clean & Green, or C & G), which has ownership over some 15,000 vacant properties, has funding to support neighborhood groups that submit a proposal to remediate and maintain vacant lots. Like Philadelphia’s PLC, the C & G program in Flint requires neighborhood groups that receive funding to clean and mow the lot once every three weeks and perform additional maintenance if they desire. A study compared streets in the year before and after the C & G program was implemented with streets that had un-remediated vacant parcels of land. It found significant reductions in violent crimes after the program had been implemented: roughly a 39% reduction in assaults.[26]

The results from the studies of vacant-lot remediation programs in Philadelphia, Youngstown, and Flint show that these programs can be designed to be scalable to entire cities and replicable across different settings. City governments like Baltimore and Chicago have also begun partnerships with community groups and local residents to clean and green blighted and abandoned lots.

Today, a growing body of high-quality studies demonstrates that abating vacant land in an urban neighborhood can dramatically reduce crime. The changes do not require large-scale structural investments from taxpayers. Rather, they require local partnerships between landscape workers, contractors, and municipal organizations to simply and quickly clean up blighted blocks—opportunities that local residents often welcome, if not outright request.

Given that crime and related problems are highly concentrated in the same places, this means that strategic planning can have large-scale population benefits. Imagine a likely scenario where a hundred blocks in a city are responsible for 20% of all serious crime. Addressing blight on these blocks alone could translate into a 5%–10% reduction in crime for the entire city. As a means of reducing crime and the fear that it creates in urban neighborhoods, changing places is often easier than changing people.

About the Authors

John M. MacDonald is professor of criminology and sociology at the University of Pennsylvania. His current research focus is on how policies and programs to change the land use of places can reduce crime and violence in neighborhoods. This research includes a randomized community trial of the effect of vacant lot remediation and stabilization on violence and injury outcomes, and a randomized trial of abandoned housing remediation on substance abuse and violence. He also studies racial disparities in criminal justice processing and ways to reduce these disparities through policy and program reforms.

MacDonald’s work has been published in journals across a variety of disciplines, including the Proceedings of the National Academy of SciencesAmerican Journal of EpidemiologyAmerican Journal of Public HealthCriminology, Economic Journal, Journal of American Statistical Association, and Journal of Royal Statistical Society. He holds an M.A. and Ph.D. from the University of Maryland and a B.A. from Vassar.

Charles C. Branas is professor of epidemiology and chairman of the Department of Epidemiology at Columbia University’s Mailman School of Public Health. His research on the geography and factors underpinning gun violence has been cited by the U.S. Supreme Court and Congress. Branas has also led large-scale scientific work that has shown how the remediation of vacant lots, abandoned buildings, and other blighted spaces can improve public health and safety.

His research has been published in journals including the British Medical JournalNew England Journal of MedicineProceedings of the National Academy of SciencesJournal of the American Medical AssociationAmerican Journal of Epidemiology, and American Journal of Public Health. He is co-author, with John M. MacDonald and Robert J. Stokes, of Changing Places: The Science and Art of New Urban Planning (Princeton University, 2019). Branas holds a Ph.D. from Johns Hopkins University’s Bloomberg School of Public Health and a B.A. from Franklin and Marshall College.  


  1. Sections of this paper have been adapted from John M. MacDonald, “Community Design and Crime: The Impact of Housing and the Built Environment,” Crime and Justice 44, no. 1 (September 2015): 333–83.
  2. Clifford Robe Shaw and Henry Donald McKay, Juvenile Delinquency and Urban Areas: A Study of Rates of Delinquency in Relation to Differential Characteristics of Local Communities in American Cities (Chicago: University of Chicago Press, 1972).
  3. David Weisburd, Elizabeth R. Groff, and Sue-Ming Yang, The Criminology of Place: Street Segments and Our Understanding of the Crime Problem (New York: Oxford University Press, 2012).
  4. David Weisburd, “The Law of Crime Concentration and the Criminology of Place,” Criminology 53, no. 2 (May 2015): 133–57.
  5. Based on calculations from Philadelphia Police Department data.
  6. Robert J. Sampson, Great American City: Chicago and the Enduring Neighborhood Effect (Chicago: University of Chicago Press, 2012).
  7. Edward L. Glaeser and Joshua D. Gottlieb, “The Economics of Place-Making Policies,” National Bureau of Economic Research, Working Paper 14373, October 2008.
  8. James Q. Wilson, Thinking About Crime (New York: Vintage, 1983).
  9. Leo Schuerman and Solomon Kobrin, “Community Careers in Crime,” Crime and Justice 8 (1986): 67–100.
  10. Clarence Ray Jeffrey, Crime Prevention Through Environmental Design (Beverly Hills, CA: Sage Publications, 1971); Ronald V. Clarke, “Situational Crime Prevention,” Crime and Justice 19 (1995): 91–150.
  11. Peter K. B. St. Jean, Pockets of Crime: Broken Windows, Collective Efficacy, and the Criminal Point of View (Chicago: University of Chicago Press, 2008).
  12. Paul Michael Cozens, Greg Saville, and David Hillier, “Crime Prevention Through Environmental Design (CPTED): A Review and Modern Bibliography,” Property Management 23, no. 5 (2005): 328–56.
  13. Eugenia Garvin et al., “More than Just an Eyesore: Local Insights and Solutions on Vacant Land and Urban Health,” Journal of Urban Health 90, no. 3 (November 2012): 412–26.
  14. James Q. Wilson and George L. Kelling, “Broken Windows,” Atlantic, March 1982, p. 29.
  15. John Snow, On the Mode of Communication of Cholera (London: John Churchill, 1855).
  16. Charles C. Branas and John M. MacDonald, “A Simple Strategy to Transform Health, All Over the Place,” Journal of Public Health Management and Practice 20, no. 2 (March–April 2014): 157.
  17. Alan Mallach, “Facing the Urban Challenge: The Federal Government and America’s Older Distressed Cities,” Metropolitan Policy Program at Brookings Institution, May 2010. For a description of block-busting that helped spur “white” flight, see Wesley Skogan, “Fear of Crime and Neighborhood Change,” Crime and Justice 8 (1986): 203–29.
  18. Pennsylvania Horticultural Society, LandCare Program.
  19. Charles C. Branas et al., “A Difference-in-Differences Analysis of Health, Safety, and Greening Vacant Urban Space,” American Journal of Epidemiology 174, no. 11 (December 2011): 1296–1306.
  20. Charles C. Branas et al., “Citywide Cluster Randomized Trial to Restore Blighted Vacant Land and Its Effects on Violence, Crime, and Fear,” Proceedings of the National Academy of Sciences 115, no. 12 (March 2018): 2946–51; Ruth Moyer et al., “Effect of Remediating Blighted Vacant Land on Shootings: A Citywide Cluster Randomized Trial,” American Journal of Public Health 109, no. 1 (January 2019): 140–44.
  21. Megan Heckert and Michelle Kondo, “Can 'Cleaned and Greened' Lots Take on the Role of Public Greenspace?” Journal of Planning Education and Research 38, no. 2 (June 2018): 211–21.
  22. Eric Klinenberg, Palaces for the People: How Social Infrastructure Can Help Fight Inequality, Polarization, and the Decline of Civic Life (New York: Crown, 2018).
  23. Rob T. Guerette and Kate J. Bowers, “Assessing the Extent of Crime Displacement and Diffusion of Benefits: A Review of Situational Crime Prevention Evaluations,” Criminology 47, no. 4 (November 2009): 1331–68. The specifically find that out of 272 place-based crime-prevention programs studied, 23% find evidence of displacement and 37% find a diffusion of benefits.
  24. Charles C. Branas et al., “Urban Blight Remediation as a Cost-Beneficial Solution to Firearm Violence,” American Journal of Public Health 106, no. 12 (December 2016): 2158–64.
  25. Michelle Kondo et al., “Effects of Greening and Community Reuse of Vacant Lots on Crime,” Urban Studies 53, no. 15 (November 2016): 3279–95.
  26. Justin E. Heinze et al., “Busy Streets Theory: The Effects of Community‐Engaged Greening on Violence,” American Journal of Community Psychology 62, nos. 1–2 (September 2018): 101–9.