Reporting of unknown drug test results in the Fatality Analysis Reporting System and associated factors, 2000-2020.

The percentage of unknown test results in FARS drug data is decreasing, and the significant associated factors found in this study may help identify additional strategies for reducing unknown drug test results. Future research should focus on continued improvement of FARS data, given the importance of FARS in understanding fatal crashes and informing strategies for prevention of crash-related injuries and fatalities in the United States.