Illinois Stop Data
Illinois traffic and pedestrian stop data, made visual.
Illinois police departments report who they stop. Since 2004 officers have recorded the race of the drivers they stop, and since 2016 the race of the pedestrians too. The Illinois Department of Transportation (IDOT) publishes the results, department by department, in more than a thousand pages of PDF tables. This site turns those tables into pictures anyone can read.
In conversations about this data there was a lot of confusion about what it is telling us. We're not all data scientists, and complex data sets can be hard to interpret. Sometimes making data more visual helps us understand what's going on in the numbers. That is the purpose of this site.
Check your department
Pick a police department and a year to see how often it stops Black, Hispanic and White drivers compared with the community it serves, and how that has changed over the years.
Check your department →See how departments compare
Every department's numbers side by side for a year, with the caveats built in: a minimum number of stops, the benchmark each department used, and what kind of department it is.
See the rankings →Reading the numbers
The headline number is the rate ratio vs. White. It compares how often a group is stopped, relative to its share of the population, with how often White drivers are. A ratio of 1.0 means the two are stopped at the same rate. A ratio of 2.0 means that group is stopped at twice the White rate.
A ratio above 1.0 is not proof of bias. The typical department sits above 1.0, and the number depends on who lives in an area, who drives through it, and how the population is counted. Numbers based on only a few stops can swing widely, so the site flags them.
About the data
The numbers come from IDOT's Illinois Traffic and Pedestrian Stop Study, covering 2004 through 2025. Each police department is responsible for the accuracy of its own data.
The way the population is counted for comparison has changed over the years. Through 2018 IDOT estimated only the share of drivers who are minority. For 2019 and 2020 it used the population of the county or city. Since 2021 it has used crash-based and distance-based estimates for traffic stops. The site marks those changes wherever they matter, because a number can mean something different on each side of one.
This is an independent project and is not affiliated with IDOT. The code, and the program that reads the PDFs, are on GitHub.