The Incidence and Role of Drugs in Fatally Injured Drivers

Terhune, K. W.; Ippolito, C. A.; Hendricks, Donald L.; Michalovic, J. G.; Bogema, S. C.; Santinga, P.; Blomberg, Richard D.; Preusser, David F. · 1992 · ROSA P / United States. National Highway Traffic Safety Administration

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Summary

This study, conducted by the Accident Research Group for the National Highway Traffic Safety Administration (NHTSA), investigated the prevalence and causal role of drugs in fatal motor vehicle crashes. Motivated by previous estimates that 10–15% of fatally injured drivers had non-alcoholic drugs in their systems, the research aimed to provide a broader, geographically diverse assessment of drug involvement and determine whether specific substances contributed to crash causation. The methodology involved collecting whole blood specimens from 1,882 fatally injured drivers across seven states (Massachusetts, North Carolina, Wisconsin, California, Nevada, Texas, and Virginia) over a 14-month period in 1990–1991. Eligible drivers were operators of passenger cars, trucks, or motorcycles who died within four hours of the crash. Specimens were analyzed for alcohol and 43 other drugs, including cannabis, cocaine, amphetamines, and various prescription medications. To assess causal roles, the researchers employed "responsibility analysis," rating each driver’s responsibility for the crash without knowledge of drug status. If drug-present drivers were disproportionately judged responsible compared to drug-free drivers, it indicated impairment. Data were supplemented by police reports, coroner records, and the Fatal Accident Reporting System (FARS). The results indicated that alcohol was the predominant substance, found in 51.5% of specimens, with 42.6% of drivers having a blood alcohol concentration (BAC) of 0.10% or higher. Non-alcoholic drugs were present in 17.8% of drivers. The most prevalent non-alcoholic drugs were cannabis (6.7%), cocaine (5.3%), benzodiazepines (2.9%), and amphetamines (1.9%). Alcohol was frequently co-present with other drugs; for instance, it was found in 83.3% of cocaine cases and 68.8% of cannabis cases. Responsibility analysis revealed statistically significant impairment effects for alcohol alone and for combinations of alcohol and other drugs. However, drivers with THC-only or cocaine-only did not show higher responsibility rates than drug-free drivers. Logistic regression suggested that impairment effects were additive, with responsibility rates increasing significantly with the number of non-alcohol drugs present. Drivers involved in drug-related crashes were predominantly male, aged 25–54, and had histories of traffic violations. The study concludes that while alcohol remains the dominant drug problem in fatal crashes, drugs other than alcohol present a limited but significant risk, particularly when combined with alcohol or used in multiples. The findings suggest that drug impairment effects may be additive and that drug use is often part of a broader pattern of high-risk behavior. The authors recommend further research to investigate additive effects at sub-intoxication alcohol levels and note that regional variations in drug prevalence exist.

Key finding

Drivers with alcohol alone or alcohol-drug combinations had significantly higher crash responsibility rates than drug-free drivers, while drivers with only non-alcohol drugs did not show elevated responsibility rates.

Methodology

naturalistic

Sample size: 1882

Provenance

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

Topics

Ranked by relevance to this paper. Hover a topic for its definition.

• illicit drugs
• polydrug
• cannabis
• incidence prevalence
• alcohol
• prescription meds

Information type

What kind of knowledge this paper contributes, grouped by family — independent of topic (what it is about) and method (how it was studied).

• Empirical Findings: crash risk outcomes, observational prevalence
• Methodological Resource: dataset resource