Impact of the Legalization and Decriminalization of Marijuana on the DWI System: Highlights from the Expert Panel Meeting

NHTSA · 2017 · ROSA P / United States. Department of Transportation. National Highway Traffic Safety Administration

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Summary

This report summarizes the findings of an expert panel convened by the National Highway Traffic Safety Administration (NHTSA) and the Governors Highway Safety Association (GHSA) to assess the impact of marijuana legalization and decriminalization on state Driving While Impaired (DWI) systems. Motivated by the rapid expansion of medical and recreational marijuana laws across the United States, the study aimed to identify operational changes, lessons learned, and necessary evaluation metrics for states navigating this legal shift. The panel included professionals from states with enacted laws, such as Colorado, Washington, and California, representing law enforcement, prosecution, adjudication, toxicology, and highway safety. The methodology consisted of a one-and-a-half-day expert panel meeting, serving as Phase I of a two-phase research project. Participants discussed seven key areas: law enforcement, prosecution, court administration, forensic laboratories, data systems, highway safety operations, and public communication. The discussions focused on identifying systemic changes following legalization, evaluating what strategies succeeded or failed, and determining appropriate quantitative and qualitative measures for future evaluation. The panel highlighted that while legalization generates tax revenue, it also imposes significant, often unanticipated costs on the DWI system, including increased demands for training, staffing, and laboratory testing. Key findings indicate substantial strain on the criminal justice infrastructure. Law enforcement must shift focus from possession charges to detecting impairment, requiring enhanced training in standardized field sobriety tests and drug recognition. Prosecutors face challenges due to the lack of scientific consensus on per se THC limits, with some jurisdictions finding statutory limits like 5 nanograms unsupported by evidence. Toxicology laboratories reported severe backlogs, funding shortages, and inconsistent testing practices, with some states experiencing delays of up to 18 months for method validation. Data systems were identified as a critical weakness, with a lack of standardized pre-legalization data making it difficult to assess true impacts on crash risk. Notably, while THC presence among drivers has increased, adjusted crash risk studies did not show a statistically significant increase in crashes associated with THC when controlling for demographic factors. The report concludes that successful management of marijuana legalization requires proactive planning, including securing funding from new tax revenues to support DWI system needs. It emphasizes the necessity of collaboration among stakeholders, including the marijuana industry, to develop public education campaigns that clarify the distinction between legal use and illegal impaired driving. The panel recommended specific measures for Phase II of the study, such as tracking pre- and post-legalization levels of marijuana in crashes and arrests, to better evaluate the long-term effects on traffic safety. The findings underscore the need for standardized toxicological reporting, improved data integration, and targeted training for legal professionals to ensure effective enforcement and adjudication of drug-impaired driving cases.

Key finding

The expert panel identified that legalization of marijuana creates unanticipated costs and operational challenges for DWI systems, particularly regarding the need for specialized training, standardized toxicology testing, and public education to counter the perception that legal use implies safe driving.

Methodology

mixed_methods

Provenance

The full processing record for this entry. Every stage of this paper's journey through the pipeline is logged — what ran, with which tool and model, how many attempts it took, and when it last completed. Discovered via bulk_ingest_rosap on 2026-05-23 (6 acquisition events logged).

Summary generated by qwen3.6-27b-prismaquant on 2026-06-10; verification: verified.

Topics

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• illicit drugs
• cannabis
• dui enforcement
• drowsy as impairment
• polydrug

Information type

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• Applied Guidance: policy recommendations