Studying impaired driving in the real-world is not simple. You cannot ethically stage dangerous scenarios on public roads. That challenge pushed researchers at Virginia Tech to follow drivers over time, observing how cannabis use affects everyday trips.
Kaitlyn Bedwell of the Virginia Tech Transportation Institute said most studies miss how people adapt over time. By tracking 14,700 trips between 2021 and 2023, researchers aimed to see behavior as it actually unfolds on real roads.
The method dates back to the 1990s at the Virginia Tech Transportation Institute. Researchers install cameras and sensors inside participants’ personal vehicles, quietly recording daily driving. Drivers also keep journals, giving context to trips taken both sober and after cannabis use.
Kaitlyn Bedwell said most research fails to follow drivers over time, missing how behavior shifts. “Since the effect of cannabis and impairment is so individualized, this study shows use over time,” she explained, emphasizing the value of long-term observation.
As mentioned, between 2021 and 2023, the team tracked 14,700 trips by drivers ages 21 to 71. That scale matters. It allows researchers to compare patterns across days, routes, and routines, building a detailed picture of real behavior.
Early analysis revealed clear time patterns. Cannabis-related trips increased around typical lunch hours and again in the evening. Fridays stood out as the most common day for use, suggesting behavior follows predictable weekly routines.
Researchers also noticed behavioral shifts. Some drivers chose different routes after using cannabis, often favoring rural roads over busier corridors. That change signals awareness. Participants appeared to adjust, possibly attempting to lower stress or exposure to traffic.
Bedwell said real-world data captures complexity that short snapshots miss. Drivers do not behave the same every day. These findings show patterns, not panic, and give policymakers measurable information instead of assumptions.
Researchers argue simulators cannot fully replicate real traffic pressure. In a lab, drivers know mistakes carry no real consequences. On public roads, choices matter. That difference, they say, changes behavior in ways short experiments simply cannot capture.
“It allows for a precise assessment of driving performance in the real-world,” Bedwell explained, noting artificial settings lack the variability of other drivers. Without real consequences, participants may take risks they would otherwise avoid.
Field studies also track habits over months and years, not just a single afternoon. That longer lens helps regulators, safety officials, and transportation planners evaluate impairment policies using sustained evidence rather than isolated test results.
As more states legalize cannabis, questions about road safety grow sharper. Lawmakers, police, and public health officials are weighing how to measure impairment fairly. Studies like this add context to a debate often driven by assumptions instead of sustained evidence.
The 2025 report gives regulators data tied to 14,700 real trips, not hypotheticals. That matters. As Bedwell noted, driving behavior is individualized, which means future policy discussions will likely focus on nuance rather than one-size fits all limits.