Effects of Drugs and Alcohol on Driver Performance
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Summary
This 1972 report by the University of California, Los Angeles (UCLA), prepared for the National Highway Traffic Safety Administration (NHTSA), investigates the effects of marijuana, Librium (chlordiazepoxide), and Dexedrine (dextroamphetamine) on driver performance, both individually and in combination with alcohol. The study was motivated by the increasing prevalence of drug use and the potential for synergistic effects between drugs and alcohol to impair driving safety. Previous research had established that alcohol primarily impairs divided attention rather than basic vehicle control skills; thus, this study aimed to determine if the selected drugs similarly affected the cognitive capacity required for safe driving. The researchers employed a factorial experimental design using two distinct testing environments: a soundproof chamber for auditory divided-attention tasks and a driving simulator for visual divided-attention tasks. In the simulator, participants performed a primary driving task while simultaneously responding to a subsidiary visual stimulus (a light) to measure reaction times under varying levels of task loading. The study compared the effects of the three drugs against placebo controls and alcohol, analyzing metrics such as reaction time, vehicle control scores, and error rates. The results were largely statistically inconclusive due to high variability in subject performance. In the laboratory auditory task, Librium showed no effect on performance, while alcohol negatively impacted results as expected. In the driving simulator, marijuana showed no statistically significant effect on performance, though a trend suggested impaired visual divided attention. Librium demonstrated a statistically significant decrement in performance at the 0.05 probability level, though the actual percent change was small (4.76%); notably, alcohol showed no significant effect despite a larger 26.8% change in performance. Dexedrine results were marginal (0.10 probability level). However, the abstract notes that Dexedrine decreased reaction times and appeared to offset the impairing effects of alcohol on reaction time, producing results similar to sober placebo drives. Vehicle control scores were generally unaffected, except for increased variability. The authors conclude that marijuana and Librium affect visual divided attention while driving, but further study with better subject screening and control is required to draw definitive conclusions. Dexedrine appears to mitigate alcohol-induced delays in reaction time. The NHTSA determined that no firm conclusions could be drawn regarding the specific effects of these drugs on driver performance based on this data alone, citing the large variation in subject scores as a primary limitation. The study highlights the complexity of measuring drug impairment in driving, suggesting that standard vehicle control metrics may fail to capture cognitive deficits in divided attention.
Key finding
Librium significantly increased reaction time in the driving simulator's visual subsidiary task, while dexedrine decreased reaction time and offset alcohol's effects, whereas marihuana showed no statistically significant impact on vehicle control or auditory attention tasks.
Methodology
mixed_methods
Provenance
The full processing record for this entry. Every stage of this paper's journey through the pipeline is logged — what ran, with which tool and model, how many attempts it took, and when it last completed. Discovered via bulk_ingest_rosap on 2026-05-23 (6 acquisition events logged).
| Stage | Outcome | Tool | Model | Prompt | Attempts | Completed |
|---|---|---|---|---|---|---|
| discover | success | rosap | — | — | 2 | 2026-05-23 |
| archive | success | — | — | — | 1 | 2026-05-23 |
| extract | success | cached | — | — | 2 | 2026-06-10 |
| clean | success | — | — | — | 1 | 2026-06-01 |
| chunk | success | — | — | — | 1 | 2026-06-01 |
| embed | success | — | — | — | 1 | 2026-06-02 |
| enrich | success | — | — | — | 1 | 2026-05-23 |
| promote | success | — | — | — | 1 | 2026-05-23 |
| summarize | success | llm | qwen3.6-27b-prismaquant | summ-v5 | 3 | 2026-06-10 |
| tag | success | vector_similarity | — | — | 19 | 2026-06-11 |
| verify | success | — | — | — | 2 | 2026-06-10 |
Summary generated by qwen3.6-27b-prismaquant on 2026-06-10; verification: verified.
Topics
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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: behavioral performance data, physiological data
- Methodological Resource: validation psychometrics