Direct messaging works best to encourage safer driving after cannabis use

Cannabis-impaired driving is an increasing public health concern. Effective communication strategies are essential for shaping risk perceptions, influencing normative beliefs, and encouraging safer behaviors. UC San Diego Transportation Research and Education for Driving Safety Center evaluated how cannabis consumers perceive and respond to cannabis-impaired driving messages, message sources, and strategies to promote safer driving behaviors. Eligible participants were adults who reported cannabis use within the past three months, perceived it as safe to drive on the same day of use, and resided in one of eight U.S. states selected for diversity in cannabis policy contexts. The study aimed to recruit 800 participants. Using a cross-sectional, mixed-methods design, participants reported cannabis use patterns and driving behaviors before reviewing a series of cannabis-impaired driving messages. Messages were developed through an iterative process informed by literature, expert review, and formative testing, and represented communication styles commonly used in safety campaigns. Participants rated each message on attention, appeal, relevance, believability, influence on behavioral intentions, and source credibility. 846 cannabis users participated. Messages emphasizing concrete effects and impairment (e.g., Feel Different, Drive Different) consistently received the highest ratings across attention, appeal, relevance, and believability. In contrast, more informational or evaluative messages (e.g., Studies Show) performed significantly less favorably. Factual messages yielded the highest proportion of participants reporting they were very likely to increase wait time before driving (59%), while self-reflective messages were most effective in encouraging alternative transportation (55%). All message types produced similar effects on intentions to remain in the same location (56-58%), and substantially fewer participants reported intentions to reduce cannabis use overall (23-29%). Message responsiveness varied by driving risk profile. Ultra-high-risk drivers reported lower likelihood of engaging in safer behaviors compared with medium- and high-risk drivers, although differences were not uniformly statistically significant. Qualitative findings indicated that exaggerated, fear-based, or stigmatizing messages were viewed negatively across groups, whereas messaging that was clear, evidence-based, and nonjudgmental was perceived as credible and effective. Source trust also varied, with healthcare providers and science-based organizations rated most credible and celebrities and social media influencers rated least trustworthy. This study offers new evidence on how cannabis users respond to messaging about cannabis-impaired driving. Messages emphasizing concrete effects and impairment, particularly those that are factual, direct, and evidence-based, were most consistently associated with higher ratings on outcome measures. However, differences in behavioral intentions across message types were modest, with limited impact on intentions to reduce cannabis use. Findings also indicate that individuals reporting higher-risk cannabis use and driving behaviors, particularly ultra-high-risk drivers, may be less responsive to messaging overall and may require more tailored approaches and complementary strategies to mitigate impaired driving. Across groups, messages perceived as exaggerated, stigmatizing, or fear-based were viewed as less credible and potentially counterproductive. These results can inform the development of user-centered, harm-reduction safety campaigns as cannabis legalization expands, while underscoring the need for continued evaluation and refinement of messaging strategies.