Among 563 German cannabis users who drive, latent class analysis found 48% were low-risk, 30% specifically engaged in cannabis-impaired driving with low perceived risk, and 22% showed a global pattern of risky behavior.
Traffic safety researchers, policymakers setting cannabis driving limits, and prevention program designers.
What the researchers found
Three classes emerged: 'Low risk' (48%) with minimal DUIC and risky behaviors; 'DUIC-specific risk' (30%) with high cannabis-impaired driving, peers who also drive high, and low perceived risk, but no other risky behaviors; and 'Global risk' (22%) with multiple risky behaviors and risk factors. Younger age and male gender predicted higher-risk class membership.
Why it matters
Not all cannabis users who drive high are the same. The 30% who specifically drive under the influence without other risky behaviors may respond to different interventions (education, peer norms) than the 22% with global risk patterns (who may need broader support). Germany recently raised its legal THC driving threshold, making this segmentation timely.
The numbers in context
N=563 German drivers using cannabis at least monthly. Low risk: 48%. DUIC-specific risk: 30%. Global risk: 22%. DUIC-specific class associated with younger age and male gender. Global risk class associated with younger age. Pre-legalization data from 2023.
How the study worked
Latent Class Analysis of 2023 pre-legalization survey data from 563 German drivers who use cannabis at least monthly. Environmental and individual risk factors and risky traffic behaviors were used as indicators, with sociodemographic covariates.
What this study cannot tell us
Pre-legalization survey may not reflect post-legalization behavior. Self-reported driving behavior is subject to social desirability bias. German driving culture and infrastructure may differ from other countries. At-least-monthly cannabis use is a relatively high threshold that may miss occasional users who also drive impaired.
How to read the evidence
Appropriate statistical method (LCA) applied to a relevant sample, but self-reported data and pre-legalization timing limit applicability to current conditions.
When this study was published
Published 2025, using 2023 pre-legalization survey data from Germany.
The bigger picture
As more jurisdictions legalize cannabis, determining THC driving limits and enforcement strategies requires understanding who drives high and why. A one-size-fits-all approach may miss the distinct risk profiles this study identified, potentially wasting resources on low-risk users while under-serving high-risk groups.
Questions still open
- Whether the DUIC-specific risk group's low perceived risk can be changed through educational campaigns
- How these risk profiles shift after legalization and changes to THC driving thresholds
Common questions
What is the DUIC-specific risk group?
Does this mean almost half of cannabis users who drive are safe?
Read the original research
Correlates of driving under the influence of cannabis: A latent class analysis.
Journal of safety research, 95, 330-337
Citation
Schranz, Anna; Verthein, Uwe; Rosenkranz, Moritz; Knoche-Becker, Anja; Manthey, Jakob. (2025). Correlates of driving under the influence of cannabis: A latent class analysis.. Journal of safety research, 95, 330-337. https://doi.org/10.1016/j.jsr.2025.10.012
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