Driving and cannabis use: a questionnaire about knowledge and behaviors after the legalization of recreational cannabis in California
DOI: 10.1186/s12889-025-24309-4
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Summary
This study investigates driving-related knowledge, attitudes, and behaviors among California adults following the implementation of Proposition 64, which legalized recreational cannabis in 2018. The research addresses a critical public health gap: while cannabis is now the most frequently used impairing substance in the U.S., there are no widely accepted blood concentration limits for impairment, and little is known about public awareness of specific driving regulations. The authors aimed to determine if legalization has influenced driving behaviors and to assess the correlation between regulatory knowledge and adverse driving outcomes. The study utilized data from the "Impact 64" survey, conducted between December 2022 and February 2023. Researchers employed a mixed-methods questionnaire design, initially screening 15,208 participants demographically matched to the 2020 California Census. A subset of 5,178 participants completed a detailed questionnaire, categorized into current users (n=4,020), former users (n=523), and non-users (n=635). Statistical analysis included chi-square tests for descriptive comparisons and multivariable logistic regression to adjust for demographic factors such as age, gender, race, and income. The study defined cannabis use as the consumption of THC-containing products. Key findings reveal mixed awareness of driving regulations among current cannabis users. While 74% knew that driving under the influence of cannabis (DUIC) could result in a citation, only 62% were aware that smoking or ingesting cannabis in a moving vehicle is prohibited, and 59% knew that cannabis containers must remain sealed. Regarding safety perceptions, 64% of current users felt safe to drive within three hours of inhaling flower products, and 55% felt safe within five hours of consuming edibles. Multivariable analysis indicated that individuals who started using cannabis at age 17 or younger were significantly more likely to perceive it safe to drive shortly after use. Crucially, lower knowledge of Prop 64 driving regulations was associated with higher rates of adverse outcomes; participants with incorrect beliefs about legality were two to six times more likely to report being pulled over or involved in a crash while under the influence. Additionally, 13% of current users reported that legalization increased their likelihood of DUIC. The study concludes that six years after legalization, significant gaps remain in public understanding of cannabis-related driving laws. The association between poor regulatory knowledge and increased crash or citation rates suggests that self-assessment of impairment is insufficient for ensuring road safety. The authors emphasize the need for effective public messaging campaigns to improve awareness of legal restrictions, clarify the duration of intoxication, and promote safe driving behaviors to mitigate public health risks associated with cannabis legalization.
Key finding
Lower knowledge of cannabis driving regulations among current users was associated with an increased likelihood of adverse driving outcomes, such as being pulled over or involved in a crash while under the influence.
Methodology
survey
Sample size: 5178
Provenance
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| Stage | Outcome | Tool | Model | Prompt | Attempts | Completed |
|---|---|---|---|---|---|---|
| discover | success | author_sweep | — | — | 2 | 2026-05-28 |
| archive | success | canonical_url | — | — | 1 | 2026-06-04 |
| extract | success | cached | — | — | 3 | 2026-06-10 |
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| embed | success | embed | Qwen/Qwen3-Embedding-8B | — | 1 | 2026-06-04 |
| enrich | success | — | — | — | 1 | 2026-05-28 |
| promote | success | — | — | — | 1 | 2026-06-04 |
| summarize | success | llm | qwen3.6-27b-prismaquant | summ-v5 | 2 | 2026-06-10 |
| tag | success | vector_similarity | — | — | 15 | 2026-06-11 |
| verify | success | — | — | — | 2 | 2026-06-10 |
Summary generated by qwen3.6-27b-prismaquant on 2026-06-10; verification: verified.
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- Empirical Findings: observational prevalence