Evaluation of the causal impact of recreational marijuana legalisation on traffic safety in the US
File(s)
Published version
Author(s)
Anupriya
Mccoy, Emma
Graham, Daniel J
Type
Journal Article
Abstract
Since the legalisation of recreational marijuana in certain US states, traffic fatalities involving drivers testing positive for marijuana have markedly increased, thereby prompting the need to understand how this policy change affects road safety. While marijuana is well-known to impair driving, determining if its recreational use directly causes more traffic fatalities remains contentious due to challenges in roadside impairment testing. Additional challenges arise because (i) Simulations may not accurately replicate driver impairment and road conditions, (ii) Estimation based on observational data must adjust for (unobserved) confounding factors, requiring an innovative model to generate causal inference, and (iii) The dynamic, evolving nature of the process requires capturing temporal relationships. This paper contributes by employing a rigorous study design based on an augmented synthetic control method to assess the causal impact of recreational marijuana legalisation on traffic fatalities. It identifies a consistent but lagged pattern of increased fatality rates in several states post-legalisation, with the effect primarily linked to the drug’s retail availability. These findings disprove any prevailing conjectures that dismiss the link between recreational marijuana use and fatal traffic crashes, highlighting the need for informed policy responses.
Date Issued
2025-09
Date Acceptance
2025-05-08
Citation
Accident Analysis and Prevention, 2025, 220 (1)
ISSN
0001-4575
Publisher
Elsevier
Journal / Book Title
Accident Analysis and Prevention
Volume
220
Issue
1
Copyright Statement
© 2025 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license ( http://creativecommons.org/licenses/by/4.0/ ).
License URL
Identifier
https://www.ncbi.nlm.nih.gov/pubmed/40543499
PII: S0001-4575(25)00192-7
Subjects
ALCOHOL POLICIES
CANNABIS
Causality and econometrics
CRASHES
DRIVING PERFORMANCE
Drug driving
DRUG-USE
Engineering
Ergonomics
FATALITIES
LAWS
LEGALIZATION
Life Sciences & Biomedicine
Public, Environmental & Occupational Health
Recreational marijuana legalisation
RISK-FACTORS
Science & Technology
Social Sciences
Social Sciences - Other Topics
Social Sciences, Interdisciplinary
STATE
Synthetic control method
Technology
Traffic fatalities
Traffic safety
Transportation
Publication Status
Published
Coverage Spatial
England
Article Number
108106
Date Publish Online
2025-06-20