Cannabis-impaired fatal crash drivers were most likely to lack a valid license
Among fatally injured drivers in Norway, cannabis (THC) impairment was specifically associated with driving without a valid license, while alcohol and stimulant impairment were associated with speeding, no seatbelt, and no license.
Quick Facts
What This Study Found
THC was found above impairment limits in 4% of fatally injured drivers. Unlike alcohol and stimulants (which were associated with speeding, no seatbelt, and no license), cannabis impairment was specifically associated only with not having a valid driver license. Drug/alcohol-impaired drivers were far more likely to speed (68% vs 32%), skip seatbelts (69% vs 30%), and lack valid licenses (26% vs 1%) compared to sober drivers.
Key Numbers
772 fatally injured drivers/riders (2005-2015). Alcohol: 20%. Medicinal drugs: 10%. Stimulants: 5%. Cannabis (THC): 4%. Impaired drivers vs sober: speeding 68% vs 32%, no seatbelt 69% vs 30%, no valid license 26% vs 1%.
How They Did This
Retrospective analysis of Norwegian road traffic crash registries and forensic toxicology databases covering fatally injured car/van drivers and motorcycle riders from 2005-2015 (n=772). Multivariable logistic regression adjusted for substance groups, age, and sex.
Why This Research Matters
Understanding which risky behaviors accompany which substances can help target enforcement and prevention efforts more effectively.
The Bigger Picture
The finding that cannabis-impaired fatal crash drivers had a distinct risk profile (license issues but not speeding) differs from alcohol-impaired drivers, suggesting different intervention approaches may be needed.
What This Study Doesn't Tell Us
Norwegian data may not generalize to other countries. Only fatally injured drivers included, which may not represent all impaired driving. Post-mortem toxicology cannot determine exact impairment at time of crash.
Questions This Raises
- ?Why is cannabis impairment specifically linked to unlicensed driving?
- ?Is this about demographics of cannabis users or a direct behavioral effect?
Trust & Context
- Key Stat:
- THC found in 4% of fatally injured drivers
- Evidence Grade:
- Large registry-based study with forensic toxicology confirmation, though limited to fatal crashes in one country.
- Study Age:
- 2019 study using 2005-2015 data from Norway.
- Original Title:
- Driver-related risk factors of fatal road traffic crashes associated with alcohol or drug impairment.
- Published In:
- Accident; analysis and prevention, 131, 191-199 (2019)
- Authors:
- Valen, Anja, Bogstrand, Stig Tore(2), Vindenes, Vigdis(3), Frost, Joachim, Larsson, Magnus, Holtan, Anders, Gjerde, Hallvard
- Database ID:
- RTHC-02328
Evidence Hierarchy
Looks back at existing records to find patterns.
What do these levels mean? →Frequently Asked Questions
How does cannabis-impaired driving compare to drunk driving in crashes?
In this study, alcohol-impaired drivers were more likely to speed and skip seatbelts, while cannabis-impaired drivers were specifically associated with driving without a valid license but not speeding or seatbelt non-use.
How common was cannabis in fatal crashes?
THC above impairment levels was found in 4% of fatally injured drivers in Norway, compared to 20% for alcohol and 5% for stimulants.
Read More on RethinkTHC
Cite This Study
https://rethinkthc.com/research/RTHC-02328APA
Valen, Anja; Bogstrand, Stig Tore; Vindenes, Vigdis; Frost, Joachim; Larsson, Magnus; Holtan, Anders; Gjerde, Hallvard. (2019). Driver-related risk factors of fatal road traffic crashes associated with alcohol or drug impairment.. Accident; analysis and prevention, 131, 191-199. https://doi.org/10.1016/j.aap.2019.06.014
MLA
Valen, Anja, et al. "Driver-related risk factors of fatal road traffic crashes associated with alcohol or drug impairment.." Accident; analysis and prevention, 2019. https://doi.org/10.1016/j.aap.2019.06.014
RethinkTHC
RethinkTHC Research Database. "Driver-related risk factors of fatal road traffic crashes as..." RTHC-02328. Retrieved from https://rethinkthc.com/research/valen-2019-driverrelated-risk-factors-of
Access the Original Study
Study data sourced from PubMed, a service of the U.S. National Library of Medicine, National Institutes of Health.
This study breakdown was produced by the RethinkTHC research team. We analyze and report published research findings without making health recommendations. All interpretations are based solely on the published abstract and study data.