Motor vehicle crashes (MVCs) are a leading cause of traumatic death and injury for people aged 1–44 years old in the United States. [1] In 2020, there were 35,766 MVCs in the United States, which were associated with 38,824 deaths. [2] This equates to a death rate of 11.7 per 100,000 population and 1.34 per 100,000 vehicle miles traveled. [3,4] Despite changes in road infrastructure, vehicle design, and traffic safety legislation that took place over the late 20th century and are ongoing into the 21st century, crash and fatality numbers remain high, ranging between 15.91 - 10.28 fatalities per 100,000 population for the years of 1994–2020. [2] While organized trauma care reduces crash mortality, prevention of MVC occurrence remains a vital goal for reducing traumatic injury and death. [5]

Among other interventions, police traffic stops (PTS) are frequently used to prevent or reduce MVCs. Officers can make stops based on observed traffic violations, reasonable suspicion of criminal activity, or concerns for public safety, and specific state traffic laws and legal precedents further shape the rules governing these stops. Under conventional frameworks, PTS enhance public safety by reducing and deterring unsafe behaviors. But the usefulness of PTS in reducing MVCs remains controversial, as investigations into this association have not consistently shown a benefit. A recent national study suggested that, in aggregate, highway PTS did not prevent total or highway MVC deaths. [6] However, another recent study suggested that reprioritizing and redesigning PTS for public health can reduce both adverse crash outcomes and disparities. [7] Advocates for social justice reform have also highlighted the role of PTS in contributing to enduring racial discrimination. Evidence of persistent racial bias underlying PTS, particularly with the selection of whom to stop and whom to search, has resulted in a social justice-based push to limit policing duties, including PTS. [8,9] Because of the mixed scientific support for the efficacy of PTS in preventing MVC and the surfacing of evidence demonstrating the dependence of PTS on persistent racial bias, the benefit of PTS to society is unclear.

While some of the studies we mention have suggested limited benefits from PTS, there are factors that restrict their generalizability. A recent large national study of PTS demonstrated that state patrol (interstate) police traffic stops were not preventive of MVC fatalities. [6] However, this study did not evaluate the role of different types and non-interstate PTS. While 89% of the PTS occur on the interstate, MVCs are more frequent on non-interstate roads, with intersections as a main factor contributing to this pattern. [6,10] According to NHTSA database, intersection MVCs account for 28 percent of fatalities and roughly 58 percent of all nonfatal MVCs, while interstate MVCs account for only 13 and 9 percent, respectively. [11] Whether non-interstate or municipal PTS are associated with reduced non-interstate MVCs or MVC-related deaths remains unanswered.

This study examines the relationship of PTS among municipal police (non-interstate police) patrols on non-interstate roads and non-interstate MVCs and MVC-related deaths. We performed a multi-year analysis of several municipalities of a single state by specific reasons for the stop. We also examined the relationship between increased PTS on MVCs and MVC-related deaths compared to decreased PTS. We hypothesized that non-interstate PTS would be associated with reduced MVCs and reduced MVC-related deaths on non-interstate roads.