What is clear from the research is that race is a consistent predictor of attitudes toward the police. Hence, some researchers
argue that what happens during the stop is as important as the reason for it. So, in addition to questions about bias in the
decision to initiate a stop, questions have been asked about bias in other aspects of the traffic stop: the length of the
stop and the decision to cite, search or use force. Furthermore, researchers are exploring whether bias, if it exists, is
a department-wide culture or isolated in certain units or a select few problem officers. Resolving each of these questions
requires different data sources and different methodological approaches.
Below is a sample of research about traffic stops. The studies highlight various approaches researchers have taken to assess
racial profiling in traffic stops:
 See, for example, Smith, William R., Donald Tomaskovic-Devey, Matthew T. Zingraff, H. Marcinda Mason, Patricia Y. Warren,
and Cynthia Pfaff Write, The North Carolina Highway Traffic Study (pdf, 407 pages), Final report to the National Institute of Justice, grant number 1999-MU-CX-0022, Washington, D.C.: U.S. Department of Justice,
Office of Justice Programs, National Criminal Justice Reference Service, January 2004, NCJ 204021.
 See, for example, the discussion of benchmarks in Ridgeway, Greg, and John MacDonald, “Methods for Assessing Racially Biased Policing,” Exit Notice in Race, Ethnicity, and Policing: New and Essential Readings, ed. Stephen K. Rice and Michael D. White, New York: NYU Press,
 Pickreall, Timothy M. and Tony Jianqiang Ye, Seat Belt Use in 2008 — Race and Ethnicity Results Among Occupants Traveling With Children Exit Notice, Traffic Safety Facts: Research Note, Washington, D.C.: U.S. Department of Transportation, National Highway Traffic and Safety
Administration, National Center for Statistics and Analysis, April 2009.
 Alpert, Geoffrey P., Michael R. Smith, and Roger G. Dunham, “Toward a Better Benchmark: Assessing the Utility of Not-at-Fault
Traffic Crash Data in Racial Profiling Research,” paper presented at Confronting Racial Profiling in the 21st Century: Implications
for Racial Justice, Boston, 2003.
 Lange, James E., Kenneth O. Blackman, and Mark B. Johnson, “Speed Violation Survey of the New Jersey Turnpike: Final Report,”
submitted to the Office of the Attorney General of New Jersey, 2001.
 Montgomery County, Maryland, Department of Police, “Traffic Stop Data Collection Analysis: Third Report, 2002.
 McConnell, E. H., and A. R. Scheidegger, “Race and Speeding Citations: Comparing Speeding Citations Issued by Air Traffic
Officers With Those Issued by Ground Traffic Officers,” paper presented at the annual meeting of the Academy of Criminal Justice
Sciences, Washington, D.C., April 2001, 4–8.
 Grogger, Jeffrey, and Greg Ridgeway, “Testing for Racial Profiling in Traffic Stops from Behind a Veil of Darkness,” Journal of the American Statistical Association 101 (2006): 878–887; Worden, Robert E., Sarah J. McLean, and Andrew P. Wheeler, “Testing for Racial Profiling With the Veil-of-Darkness
Method,” Police Quarterly 15 (March 2012): 92–111.
 Alpert, Geoffrey P., Roger G. Dunham, Meghan Stroshine, Katherine Bennett, and John MacDonald, Police Officers' Decision Making and Discretion: Forming Suspicion and Making a Stop (pdf, 151 pages), Final report to the National Institute of Justice, grant number 2001-IJ-CX-0035, February 2006, NCJ 213004.
 Walker, Samuel, “Searching for the Denominator: Problems with Police Traffic Stop Data and an Early Warning System Solution,”
Justice Research and Policy 3 (2001): 63–95.
 Schell, Terry L., Greg Ridgeway, Travis L. Dixon, Susan Turner, and K. Jack Riley, Police-Community Relations in Cincinnati: Year Three Evaluation Report Exit Notice, Santa Monica, Calif.: RAND, 2007.