Cannabis remained the most commonly detected substance in drug-related traffic stops in Munich throughout the pandemic, with THC-COOH levels rising during lockdowns.
Traffic safety researchers, law enforcement, and policymakers working on cannabis and driving policy.
Cannabis was detected in 66-67% of substance-related traffic stops in Munich, stable through the pandemic
What the researchers found
Among 6,210 blood samples from substance-related traffic stops in Munich (2019-2021), cannabis was detected most frequently (66-67%), followed by alcohol (11%) and cocaine (5%). Detection patterns were largely stable across the pandemic. However, THC-COOH concentrations were higher during the pandemic, and alcohol was more common in e-scooter riders during lighter restrictions.
Why it matters
Understanding how pandemic conditions affected substance-impaired driving patterns can help cities prepare traffic safety measures during future disruptions and informs ongoing debates about cannabis and driving policy.
The numbers in context
6,210 blood samples analyzed. Cannabis detected in 66.2% pre-pandemic, 67.4% during pandemic. Alcohol: 11.7% vs 10.8%. Cocaine: 5.7% vs 5.2%. THC-COOH concentrations were higher during the pandemic. Alcohol levels rose during light restrictions and fell during strict lockdowns.
How the study worked
Retrospective analysis of 6,210 blood samples from individuals suspected of substance-related traffic offenses under German law between January 2019 and July 2021. Samples stratified by pre-pandemic and pandemic periods, with pandemic periods subdivided by restriction severity.
What this study cannot tell us
Single city (Munich) limits generalizability. Only captures individuals who were stopped and tested. Cannot determine impairment level from THC-COOH (an inactive metabolite). No data on crash outcomes or severity.
How to read the evidence
Large sample from systematic testing in a single city. Retrospective design and single-city scope limit broader conclusions.
When this study was published
2025 publication analyzing 2019-2021 data from Munich.
The bigger picture
The stability of cannabis detection rates despite pandemic disruptions suggests that cannabis-impaired driving is a persistent baseline issue rather than one driven by social circumstances. The e-scooter finding highlights emerging vehicle-specific safety concerns.
Questions still open
- Did the higher THC-COOH levels during the pandemic reflect increased use or more concentrated products?
- How do e-scooter DUI patterns compare to other European cities?
Read the original research
Quantitative and qualitative changes in substance-related administrative offences in road traffic during the SARS-CoV-2 pandemic in Munich.
PloS one, 20(10), e0334598
Citation
Holzer, Anna; Stoever, Andreas; Lau, Michael; Gleich, Sabine; Graw, Matthias; Ludwig, Anouk; Hartung, Benno. (2025). Quantitative and qualitative changes in substance-related administrative offences in road traffic during the SARS-CoV-2 pandemic in Munich.. PloS one, 20(10), e0334598. https://doi.org/10.1371/journal.pone.0334598