People were willing to buy and use more cannabis when they had more time before they needed to drive | Research

The takeaway

Using behavioral economics tasks, cannabis users adjusted their hypothetical purchasing and consumption downward as driving became more imminent, but those who perceived less danger from cannabis-impaired driving consumed more across all conditions.

Traffic safety researchers, public health communicators, cannabis policy analysts

Perceived dangerousness of cannabis-impaired driving correlated r = -0.29 to -0.62 with cannabis demand

What the researchers found

Cannabis demand (how much people would purchase and consume) was sensitive to driving latency: participants consumed more when driving was 6 hours away versus 20 minutes away. Those who perceived driving after cannabis as less dangerous showed higher cannabis demand across all conditions. The effects were statistically significant but small in magnitude.

Why it matters

Understanding what factors influence people to use cannabis before driving can inform public safety messaging. The finding that risk perception correlates with behavior suggests education about impairment risks could reduce cannabis-impaired driving.

The numbers in context

167 participants. Significant main effects of driving latency on all demand indices (p < 0.05, partial eta-squared = 0.008-0.043). Perceived dangerousness inversely correlated with demand (r = -0.29 to -0.62).

How the study worked

Cross-sectional online study of 167 adults who smoked cannabis at least monthly (77% White, 45% women, mean age 38.55). Participants completed four marijuana purchase tasks under different driving latency vignettes (no driving, 20 minutes, 1 hour, 6 hours). Demand indices included intensity, breakpoint, maximum expenditure, and price sensitivity.

What this study cannot tell us

Hypothetical purchase tasks, not real consumption. Online convenience sample. Mostly White, cannabis-experienced participants. Small effect sizes. Does not capture actual driving behavior.

How to read the evidence

Well-designed behavioral economics study, but hypothetical scenarios and a convenience sample limit real-world applicability.

When this study was published

2026 publication

The bigger picture

As cannabis legalization expands, so does the challenge of impaired driving. This study adds to the small literature showing that people do moderate their cannabis use based on driving plans, but not enough to eliminate risk, especially among those who underestimate the danger.

Questions still open

Would real-world studies confirm that driving latency affects actual cannabis consumption? Could public health campaigns shift perceived dangerousness enough to change behavior?

Common questions

What is a marijuana purchase task?

A behavioral economics tool where participants say how much cannabis they would buy and consume at different prices, used to measure demand and motivation for use under different conditions.

Did people stop using cannabis when they had to drive soon?

They used less, but many still indicated they would consume some cannabis even with driving 20 minutes away, especially those who perceived less danger.

Read the original research

Pass the Keys: Using Behavioral Economics to Explore Driving After Cannabis Use.

Substance use & addiction journal, 47(1), 134-143

View on PubMed ↗Publisher’s paper ↗

Citation

Miller, Brandon P; Aston, Elizabeth R; Spindle, Tory R; Amlung, Michael. (2026). Pass the Keys: Using Behavioral Economics to Explore Driving After Cannabis Use.. Substance use & addiction journal, 47(1), 134-143. https://doi.org/10.1177/29767342251360851