a police car with lights on engaging in a traffic stop

PPC Enters Contract with ICPD to Analyze Racial Disparities in Traffic Stops


The Public Policy Center and the Iowa City Police Department (ICPD) have entered a research partnership to analyze traffic enforcement patterns in Iowa City, following the Iowa City City Council's unanimous approval of the study on April 25. The central aim of the partnership will be to assess disparities in traffic stops and stop outcomes. The project will be led by Ethan Rogers, assistant research scientist in the Crime and Justice Policy Research Program, and Mark Berg, Interim Director of the PPC and director of the Crime and Justice Policy Research Program.

"Community-engaged research is one of the core aims of the PPC," Berg said. "We are excited to begin working with our local government agencies to better understand this important policy issue."

The project will involve three steps. First, the research team will review and summarize the completeness of the traffic stop data. They will identify patterns of missing or incomplete data to ensure that the analyses are based on an accurate representative picture of local traffic enforcement. Second, the team will provide a detailed descriptive report of enforcement in Iowa City over the past two decades.

"A thorough description of traffic enforcement - that is, where, when, why, and how stops are occurring - is an essential step," said Rogers. "We must build this foundational understanding of enforcement before we can proceed with analyses of racial disparities."

Third, the research team will conduct multiple statistical tests based on published methodologies to identify the extent to which there are racial and ethnic disparities in traffic stops. Approaches will include benchmark tests, veil-of-darkness methods, predicted disposition analyses, and hit-rate analyses. By applying various analytical strategies, the hope is to gain a more comprehensive understanding of racial disparities in traffic enforcement in Iowa City.

The contract between the PPC and ICPD will last one year and will be evaluated after the time is allotted. IC Police Chief Dustin Liston said the efforts to record this data are essential for the future of policing in Iowa City and to show transparency in the policing process, as they aim to give the police department and community insight into identifying recent trends of disparities in law enforcement.

"This traffic study will support the department's continued commitment to eliminating racial profiling, heightening awareness of implicit bias, and building trust and respect between the law enforcement and all communities and persons in Iowa City," Liston said in an article by The Daily Iowan.

Read more about the project here.