2013–2014 National Roadside Study of Alcohol and Drug Use by Drivers: Drug Results

Kelley-Baker, Tara; Berning, Amy; Ramirez, Anthony; Lacey, John H.; Carr, Katherine; Waehrer, Geetha; Moore, Christine; Pell, Karen; Yao, Julie; Compton, Richard P. · 2017 · ROSA P / United States. Department of Transportation. National Highway Traffic Safety Administration

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Summary

This report presents the drug-related findings from the 2013–2014 National Roadside Study (NRS), a nationally representative survey conducted by the National Highway Traffic Safety Administration (NHTSA) to estimate the prevalence of drug use among drivers. The study was motivated by the need for objective, biological data on drug-positive driving, as previous estimates relied heavily on self-report or postmortem data. It also aimed to establish trend data by comparing results to the 2007 NRS, the first roadside study to include drug testing. The methodology involved a stratified random sampling of non-commercial vehicle drivers at 60 sites across the continental United States. Data collection occurred during one Friday daytime session and four nighttime sessions on Friday and Saturday. Of 11,100 eligible drivers, 9,455 provided breath samples, 7,881 provided oral fluid samples, and 4,686 provided blood samples. Researchers tested for 98 substances, including over-the-counter, prescription, and illegal drugs. A two-stage testing process screened samples and then confirmed specific drugs. To ensure comparability with the 2007 study, trend analyses adjusted 2013–2014 detection thresholds to match 2007 levels. The study explicitly notes that a positive result indicates drug presence, not necessarily impairment. The results indicate that 22.3% of daytime drivers and 22.5% of nighttime drivers tested positive for drugs in combined oral fluid or blood samples. Delta-9-tetrahydrocannabinol (THC) was the most prevalent substance, found in 8.7% of daytime drivers and 12.7% of nighttime drivers. Gender analysis revealed that males had significantly higher THC prevalence than females in both daytime and nighttime sessions. Comparing the 2013–2014 data to 2007, there was a statistically significant increase in overall nighttime drug prevalence, rising from 16.3% to 20.1%. This increase was driven primarily by a significant rise in THC-positive drivers, which increased from 8.7% in 2007 to 12.7% in 2013–2014. Additionally, nighttime drivers testing positive for medications-only were significantly less likely to have detectable alcohol levels compared to those testing positive for illegal drugs. The significance of these findings lies in the documented upward trend in drug-positive driving, particularly regarding marijuana use, over a seven-year period. The study provides the first national trend data on drug prevalence among drivers using biological measures. However, the authors emphasize that because the study measures exposure rather than impairment, the data cannot be used to conclude that these drivers were impaired while driving. The findings highlight the growing presence of drugs in the driving population, informing future policy and research efforts regarding drug-impaired driving.

Key finding

Nighttime drug-positive driving prevalence increased significantly from 16.3 percent in 2007 to 20.1 percent in 2013–2014, with THC being the most common drug detected in both periods.

Methodology

naturalistic

Sample size: 9455

Provenance

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Summary generated by qwen3.6-27b-prismaquant on 2026-06-10; verification: verified.

Topics

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• illicit drugs
• polydrug
• prescription meds
• cannabis
• dui enforcement
• opioids

Information type

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• Empirical Findings: observational prevalence