The provision of street lights led, to a minimum 36 percent reduction in nighttime outdoor index crimes

A plausible causal mechanism and a large effect size. Bodes well.

From Reducing Crime Through Environmental Design: Evidence from a Randomized Experiment of Street Lighting in New York City by Aaron Chalfin, Benjamin Hansen, Jason Lerner, and Lucie Parker. From the Abstract.

This paper offers 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 streetlights were randomly allocated to public housing developments from March through August 2016. We find evidence that communities that were assigned more lighting experienced sizable reductions in crime. After accounting for potential spatial spillovers, we find that the provision of street lights led, at a minimum, to a 36 percent reduction in nighttime outdoor index crimes.