are streetlights better than the Bat-Signal?

In Matt Reeves’ new film The Batman, Thomas Wayne, Bruce Wayne’s father, sets up a public works fund of $1 billion for basic infrastructural needs and deserving charities. Back in Christopher Nolan’s Batman Begins, Thomas had built an affordable transit system for the low-income residents of Gotham.

In reality, social planners can efficiently influence crimes rates by changing the physical environment, rather than with more enforcement and incarceration. If a crime happens, the victim suffers some costs, then some others arrest the perpetrator, adjudicate them, and punish them. That’s very expensive for a lot of people, including the taxpayers. To dissuade people from offending in the first place is a lot cheaper. Typically, before a crime, an offender’s thinking about the next 10 minutes, rather than the next 10 years — not thinking about the risk of punishment. So structuring the environment to reduce crime is more effective than the threat punishing a potential criminal.

“Lighting can function as a signal, and it might have these global effects on crime not just at night, but during the daytime, because it gets people to sort of feel like a community is being cared for or being protected,” says criminology professor Aaron Chalfin, who ran the first-ever study on lighting to reduce crime. In “Reducing Crime Through Environmental Design: Evidence from a Randomized Experiment of Street Lighting in New York City,” 40 of 80 housing developments received experimental light towers, while the other 40 didn’t. The lights were used for six months, and the crime statistics between the two groups were then compared. Chaflin says:

We find substantial reductions in these outdoor nighttime index crimes on these [lighted] public housing campuses, around 60% reductions. Given that we have a relatively small sample, there is also a lot of variation in our outcome, variable crime. There is some statistical uncertainty around that estimate, but [it’s] larger than 30%. It could be as large as 80%. These are qualitatively significant results, regardless of where within the confidence interval.

This experiment was grounded in place-based crime reduction, which looks at crime spatially rather than as individual elements. The approach is often called Crime Prevention Through Environmental Design (CPTED). The idea is that urban planners seek to leverage design principles and ask, “How can we design public spaces that are less conducive to offending?” Answer: lighting, visibility, and other street conditions.

CPTED is based on Problem-Oriented Policing, in which law enforcement consider design-based challenges to reducing crime and develop strategies to control it through nontraditional means, focusing on the desired end state not just the process. CPTED is specifically based on broken windows theory, which Chaflin says is the idea that “disorder can beget more disorder, and that disorder reduction can be a critical piece of the crime reduction puzzle.” That isn’t to say there’s much evidence for the effectiveness of making tons of misdemeanor arrests, though.

Before this experiment, adding streetlights hadn’t been properly studied to see if such a measure would reduce crime, or to what degree. Maybe it would have the opposite of the intended effect, and the lights would be used by potential criminals to identify possible targets. In that case, the lights are endogenous to crime, meaning they facilitate what they’re meant to reduce.

As it turns out, it seems the increased visibility from better lighting leads to people taking precautions. Better lighting can also increase the number potential witnesses. These street-smart behaviors are referred to as target-hardening, making it more difficult for a person to become a target of a crime. Lighting also increases the effectiveness of police officers or surveillance cameras.

Additionally, investing in a community’s financial and social needs makes crime seem less needed or less attractive. The intervention of adding these “light towers” costs about $75 per resident. The community’s infrastructure creates conditions for prosocial community members to take control positively, even in subtle ways.

Okay, but what if the crime just moved down the block? The two-block radius around the tested areas were factored into the stats, to act as a buffer zone for “spillover” of crime. In New York City, the campuses which received the lighting, plus this two-block radius, had a 35-40% reduction in the crimes under examination.

The Batman opens with the caped crusader describing his need to be selective in which crimes he intervenes with. In Gotham, the Bat-Signal is “not just a call. It’s a warning.” It invites escalating crime, attracts violence, and inspires copycat vigilantes. It’s easy to think that Batman may be the epitome of over-policing.

Yet this Batman’s tactics change over time. He learns to not just attack criminals from the top down, swooping in to kick ass. Batman grows as a detective, consulting with diverse perspectives to get a fuller picture of crime, and approaching Gotham’s problems from the bottom up. In one beautiful moment, Batman uses a road flare to lead people out of danger and into the light. He’s standing among them, solving the problem. It’s the difference between crime being a riddle and crime’s shadows needing light.

AIPT Science is co-presented by AIPT and the New York City Skeptics.

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