In Chicago, more black drivers were stopped by the police than fined by speed cameras

Black drivers in Chicago are stopped by police officers more often than they are ticketed by automatic speed cameras, new research shows. They were also stopped by police disproportionately more often than one would expect given the proportion of black drivers on a road. The opposite was true for white drivers, who were disproportionately less likely to receive tickets.

While this confirms previous research into racist bias in policing, comparing police stops with cameras provides a clearer picture than police data alone.

“The difference in rates between automated and non-automated systems paints a bleak picture,” said Nebiyou TilahunAssociate Professor of Urban Planning and Policy at the University of Illinois Chicago and co-author of the study.

Research, published in the Proceedings of the National Academy of Sciencesused a database that estimates the ethnic composition of drivers on certain Chicago streets using GPS data from cell phones. The researchers compared this data to the ethnic composition of drivers who were stopped by police or received a speeding ticket on those streets. In police stops, the ethnic composition of the driver is listed in the police report. For the cameras, the researchers used the U.S. census tract to which the ticket was sent as an indicator of the driver’s ethnic composition.

The researchers found that black drivers were ticketed by cameras slightly more often than would be expected given their share of drivers on a given road. Tilahun said it’s not clear why this happened – there may have been a confounding factor, such as the driver’s age, that the researchers did not examine.

What was clear was that the police issued many more tickets to black drivers than one would expect given the proportion of black drivers on the road. On roads where 50% of drivers were black, for example, the average number of police stops was 70%.

The opposite was true for white drivers. When they made up 50% of drivers on a roadway, they accounted for, on average, less than 20% of police stops. And white drivers were, on average, responsible for a smaller share of police stops than automatic tickets, regardless of whether they made up a higher or lower share of drivers.

The findings draw attention to racial disparities in police stops, Tilahun said. While these results are not necessarily surprising, they eliminate some of the factors that could be blamed for skewing the data when only police stops are considered, such as the argument that police are more likely to patrol areas where there are high proportions of black drivers.

“In the past, you might have been able to say, ‘Well, there are confounding factors. We really can’t be sure.’ I think this makes it a lot clearer and puts it on the agenda for everyone involved that street checks need to be more racially neutral,” he said.

Co-authors of the study include Sajad Askari, a doctoral student at UIC, and researchers from Cornell University, Rutgers University and the University of Sydney.