The harmful effects of alcohol on motor vehicle safety are among the most extensively documented issues in traffic injury prevention in the United States. Foundational research on the subject dates back to the mid-1930s, when one of the first case-control studies examined the role of alcohol in crashes (Holcomb, 1938). Since then, an expansive body of scientific literature has confirmed the causal relationship between alcohol consumption and impaired driving. By 2001, the National Highway Traffic Safety Administration (NHTSA) had cataloged over 700 relevant publications on alcohol-impaired driving alone (Jones & Lacey, 2001), underscoring the depth of accumulated knowledge in this area.

Alcohol impairs numerous cognitive and physiological functions that are essential to safe driving. These include judgment, reaction time, attentional control, motor coordination, visual acuity, and depth perception (CAMH, 2024). These impairments compromise a driver’s ability to assess risk, respond to dynamic traffic conditions, and maintain control of the vehicle. Notably, these effects are present even at low blood alcohol concentrations (BACs) and can affect drivers regardless of their experience or skill level. Additionally, the consequences of alcohol-impaired driving are grimly reflected in national crash statistics. Approximately one-third of all traffic fatalities in the United States involve a driver under the influence of alcohol. In 2023, this translated to 12,429 alcohol-related fatalities—an average of one death every 42 minutes (National Center for Statistics and Analysis, 2025). These data clearly demonstrate the enduring public safety threat posed by alcohol-impaired driving, despite decades of public education, enforcement, and policy interventions.

In contrast, research on the impact of other drugs—such as cannabis, opioids, stimulants, and sedatives—on driving performance and crash risk is comparatively underdeveloped. This research gap is attributable in part to methodological and logistical challenges. Unlike alcohol, for which there is a well-defined and universally accepted metric of impairment (i.e., BAC), drug impairment lacks standardized thresholds, and many substances remain detectable in the body long after their impairing effects have subsided. Furthermore, variations in individual tolerance, polydrug use, and differences in drug metabolism complicate efforts to link drug presence to crash risk. Despite these limitations, the need to better understand drug-impaired driving has become increasingly urgent. Factors such as the rapid expansion of cannabis legalization across U.S. states, the ongoing opioid crisis, and findings from the National Roadside Surveys conducted by NHTSA (2007; 2015) point to a growing prevalence of drug use among drivers. In addition to single-drug impairment, the issue of polydrug use—the concurrent use of multiple drugs or alcohol in combination with other substances—poses a complex and underexamined threat to road safety.

Accurate, timely, and comprehensive data collection on drug-impaired driving is essential for understanding the scope and nature of this evolving problem. This includes standardized toxicological testing, improved crash reporting mechanisms, and consistent tracking of DUI enforcement outcomes across jurisdictions. High-quality data enable researchers, policymakers, and enforcement agencies to detect emerging trends in impaired driving and related traffic safety consequences; assess the real-world effects of policy changes, such as cannabis legalization; and inform the development, implementation, and evaluation of evidence-based countermeasures, including public education campaigns, roadside detection technologies, and judicial interventions.

In recognition of the growing concern surrounding alcohol- and drug-impaired driving, recent legislative action in the Commonwealth of Virginia reflects a proactive step toward improving data infrastructure and enforcement. Specifically, state law (Va. Code § 46.2-223.1) mandates the annual collection and reporting of data related to driving under the influence of alcohol, drugs, or a combination of both. This data collection process, organized by calendar year, is to be administered by the Department of Motor Vehicles (DMV). The intent of this legislation is to establish a foundational system that enhances the enforcement of DUI laws while also improving the consistency, accuracy, and comprehensiveness of related data. However, for this initiative to yield meaningful improvements in traffic safety outcomes, it is critical to first conduct a comprehensive assessment of Virginia’s current capabilities and practices across multiple dimensions of DUI data collection and reporting. Only through such an evaluation can the state begin to identify areas of inefficiency, gaps in coverage, or inconsistencies across data sources, and then develop strategies for optimal resource allocation and targeted system enhancements. To support this effort, the Virginia DMV has partnered with the Virginia Tech Transportation Institute (VTTI) to analyze previously collected data from a range of sources, including law enforcement, toxicology laboratories, judicial systems, and crash reports.