SSN Key Findings

What 20 Million Traffic Stops Reveal about Policing and Race in America

Policy field

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University of North Carolina at Chapel Hill
The University of Texas at Austin

In America’s protracted war on crime, police have used routine traffic stops as opportunities to search drivers for contraband. Police agencies have always understood that this crime-fighting strategy requires a very large number of stops for every interception of a significant drug shipment. At the same time, police have tacitly presumed – and hidden from public scrutiny – that middle-class white Americans would be mostly exempt from this aggressive approach.

In our new book, Suspect Citizens, we analyze more than 20 million traffic stops in North Carolina – using detailed data about the types of stops and particular officers involved. From these data, we document that successful drug busts are rare but the costs of many traffic stops are high. Not only have those costs been significantly underestimated, they have been borne disproportionately and persistently by young men of color. Although most traffic stops are ineffective in discovering drugs or other contraband, they alienate people subjected to them.

Tellingly, in communities where minorities have higher levels of political power, racial disparities in these stops are lower. Racial disparities are also lower for agencies that do traffic stops mainly for reasons of safety, rather than to deal with other issues like broken tail lights (an offense related to poverty) or expired tags and other regulatory infractions. As we show, simple reforms can reduce racial disparities and thus improve citizen faith in police agencies.

Ongoing Tensions between Police and Minority Communities

Police violence in minority communities has been spotlighted since the 2013 launch of the #BlackLivesMatter movement, but such problems of racially disparate policing are long-standing. Effective public responses have been undercut by the tendency of middle class white Americans to disbelieve allegations of systematic injustices. Everyone realizes a small number of rogue officers may be corrupt or racist. But most whites cannot envisage that police interactions with minority citizens are regularly harsh, something blacks and Hispanics find easy to believe.

Traffic stops are the most common form of interaction between citizens and the police, so most Americans have the unpleasant experience of seeing flashing blue lights in their rearview mirror. Yet our review of the longest-run of data on traffic stops ever collected for any state in the nation reveals the starkly different experiences different subgroups of Americans have with these stops – comparing whites and minority drivers, young and old, and males and females. Forms of treatment that seem incredible to a middle-class or middle-aged white driver turn out to be commonplace for black and Hispanic drivers, and provide a valuable context to the broader American debate about police behavior of all kinds.

North Carolina as a Test Case

In the midst of a national conversation about “Driving While Black,” North Carolina legislators, urged on by members of the Black Caucus, mandated the collection of routine traffic stop statistics. Since January 1, 2000, the state has collected data on over 20 million traffic stops. Originally, there was concern that black drivers might be stopped more than white drivers, and that a particular drug interdiction unit of the Highway Patrol could have searched black drivers as much as twice as often as it searched white drivers. Editorial writers anticipated that systematic data would reveal such allegations to be false – or, alternatively, validate the allegations and set the stage for immediate steps by police leaders to end disparate practices.

Our comprehensive analysis shows that, indeed, black drivers are about twice as likely to be stopped on the highways. And once pulled over, they experience about double the likelihood of being searched. Younger male drivers are searched at an alarmingly high rate. None of this surprises people who believed that police engage in different kinds of behaviors depending on whom they encounter. But the results nevertheless raise troubling issues of fairness and equity. And they certainly help make sense of the vastly different orientations and levels of trust in the police we see from whites and members of minority communities.

Differences That Don’t Go Away

When we dug in to make sense of the racial disparities so apparent in our data, we considered why drivers were pulled over in the first place (for example, maybe whites are usually pulled over for speeding, while blacks are stopped for equipment violations). We also considered the day of the week and time of day of the stops (maybe young black males drive later at night) as well as the age and gender of the driver. Likewise, we examined whether racial disparities could be accounted for by a few “bad apple” officers.

Our analysis finds that many of these factors do indeed affect the odds that drivers will be searched, but they cannot explain away the overall racial differences. Disparities do not disappear when we take into account legally relevant factors such as being pulled over for drunk driving or when we consider legally irrelevant differences in age or gender. Disparities are not attributable to a few officers more likely to search minorities. Nor do they happen because officers are just looking in the right place, because police agencies are often less likely to find contraband on minority drivers. When all is said and done, racially disparate search rates appear to happen because police tend to hold unwarranted suspicions about young men of color.

Reducing the High Costs of Alienation

Middle-class white Americans may find it incredible that the police would behave in ways they themselves have never experienced, but young men of color grow up with different, negative expectations that naturally reduce their trust in government. As they become less likely to cooperate with police, vote, or participate constructively in public life, the net results are highly damaging to the very fabric of American democratic life. Furthermore, crime control itself becomes much more difficult when so many members of the public, especially in high-crime areas, have reasons to become distrustful of the police.

Thankfully, as we have suggested, some straightforward reforms in traffic stops can reduce alienation, increase trust, and improve community-police relations, keeping everyone safer.

Read more in Frank R. Baumgartner, Derek A. Epp, and Kelsey Shoub, Suspect Citizens: What 20 Million Traffic Stops Tell Us about Policing and Race (Cambridge University Press, 2018).