Traffic Stop Data Collection: The Impact of Methodology on Research Regarding Race-Based Policing

Erica Leah Schmitt, Bureau of Justice Statistics
Matthew R. Durose, Bureau of Justice Statistics

ABSTRACT
In February 2002, researchers released findings from the North Carolina Highway Traffic Study (NCHTS). Various aspects of motor vehicle stops were examined, in order to determine whether racial disparities exist among drivers who were issued a citation. Accident rates were calculated for each racial/ethnic group and used as a baseline measure of risk for being involved in a traffic stop. In many instances, NCHTS researchers found that African American drivers were more likely to receive some sort of citation or written warning, when compared with accident rates for African American drivers.

This paper replicates the likelihood ratios calculated by NCHTS researchers, using data from the Police Public Contact Survey (PPCS) collected by the Bureau of Justice Statistics. The paper will feature three distinct sections. First, similarities and differences in research findings will be discussed, with particular focus on the validity and reliability of the specific NCHTS and PPCS measures employed. Second, the advantages and disadvantages of the disparate data collection methods utilized by each study will be discussed in light of the research findings. Third, suggestions will be made for improving data collection regarding racial bias by police in traffic stops, based on methodological considerations highlighted in the previous two sections of the paper.



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Updated 05/20/2006