Study yields mixed results on racial disparities during Washington State Patrol traffic stops

A new study provides five years of data on traffic stops made by Washington State Patrol, demonstrating mixed results related to racial disparities.

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The study comes courtesy of researchers at Washington State University, analyzing over 3.4 million traffic stops, 47,000 calls for service, and 175,000 collisions between January of 2015 and December of 2019.

While it says that it found “no evidence for intentional, agency-level racial bias,” it also showed some disparities in racial demographics most likely to be pulled over, cited, and searched. Over the five-year period it pulled data from, 5.7% of all traffic stops involved a Black driver, despite that demographic making up roughly 4.4% of the state’s population.

The highest rate of racial disparities involving Black drivers was seen in Pierce County, comprising 12.7% of traffic stops despite making up 7.7% of the county’s population. That was followed by King County, where Black motorists — comprising 7% of the county’s population — made up 11.5% of traffic stops.

White drivers made up 74.4% of traffic stops statewide, while comprising 78.5% of Washington’s population. Native American, Asian, Pacific Islander, and Hispanic drivers were stopped by troopers at lower rates compared to their population.

Disproportionate practices were seen among the racial groups most likely to be searched. While Native American, Hispanic, and Black drivers were more likely to be searched than white drivers, so-called “hit rates” — the rate at which searches turned up contraband — were lower among the former group compared to searches of the latter.

“Particularly for Black and Hispanic motorists, searches were less productive (10% difference in contraband found) which may indicate that probable cause standards are lower for searches of these groups,” the study notes.

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In terms of traffic citations, “white motorists received the most, but their overall proportion of total citations fell over the five-year period.” Native American and Black drivers were found to be less likely to be cited compared to white drivers, while Asian/Pacific Islander and Hispanic drivers were more likely to be cited.

Moving forward, WSU’s Division of Government Studies and Services plans to “work with WSP to study and better understand areas of apparent, unexplained disparities for Black and Hispanic drivers.”

“Researchers plan to conduct in-person focus groups with community members to learn about their experiences and relationship with officers,” it said in a press release.

You can read the full study at this link.

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