Police bicycle patrols in a Philadelphia neighborhood known for its drug market led to a "notable reduction" in social disorder crimes, but unintentionally caused more violence and drug crimes by disrupting the drug trade, a new study found. The paper by Daniel Lawrence, of CNA Corp.'s Center for Justice Research and Innovation, was published in the online journal CrimRxiv and is forthcoming in Criminology and Public Policy. Bicycle patrols can serve a dual purpose of improving trust in police and reducing violent crime, since they put officers closer to the action than when they're cocooned in a patrol car. They also improve mobility over foot patrols. The experiment, comparing the patrol areas to other identical streets, was conducted in the Kensington neighborhood, notorious for its drug markets and violence in recent years. It focused on a satellite police substation that the Philadelphia Police Department opened in January 2021 with three dozen officers working 12-hour shifts on bicycle.
After showing no significant effects at first, the program's effect on social disorder crimes seemed to grow after its first and second anniversaries, with a nearly 25% reduction after two years. But drug and violent crimes, notably shootings, increased by similar proportions or greater by the end of the second year. Property crimes showed no significant changes in the first two years. Because the bicycle patrols' chief concern was disrupting the drug market, "it is very likely that the increased presence of officers in the streets increased offenders’ belief that they could be caught when committing a public social disorder crime, such as disorderly conduct, gambling, loitering, or vandalism," the paper states. That made it "likely because of this drastic disruption of the drug market that violent person crimes and shootings simultaneously increased, an effect that has been observed in other studies." Lawrence theorized how that disruption played out. "It is possible that as officers actively patrolled the area and use the bicycle patrols to better approach drug sellers to catch them in the act of a deal, the drug market responded by introducing new, inexperienced sellers who are willing to except the high-risk position to sell drugs and this led to increased violence as dealers tried to establish themselves and the areas they wanted to control." This raises a host of policy considerations, from adequate staffing to patrol focus, that police departments should consider, Lawrence concluded. Lawrence summarized the story in a lengthy thread on the social media site formerly known as Twitter.