There has been yet another interesting study published related to cannabis impaired driving. Published in the Journal of Accident Analysis and Prevention, the study titled Predicting changes in driving performance in individuals who use cannabis following acute use based on self-reported readiness to drive, looks at how well people can tell their state of impairment after using cannabis.
The researchers found that regular users of cannabis may not be impaired after using a moderate dose of cannabis, and that they can tell if they are impaired.
The study surveyed a group of thirty individuals who used cannabis at least once per month. They were tested for a baseline by using a driving simulator while they were sober and had not smoked or consumed cannabis. Then, the participants were dosed with 6.18% THC cannabis.
After dosing, the subjects were then given a chance to use the driving simulator in 30 minute increments after using cannabis. On each occasion, they were asked if they felt they were safe or ready to drive on real roadways. Subjects also had a blood draw to measure their corresponding blood THC levels at each interval, in order to see if their was correlation between their THC concentration and the driving performance.
The simulator monitored driving performance by measuring their standard deviation from the lane position, the average speed, the number of lane departures and compared with the baseline from pre-dose performance.
For those drivers who indicated they were not ready to drive, the simulator showed a 2.6 centimetre decrease from the baseline on their standard deviation from the lane position. Average vehicle speeds were decreased, as opposed to increased, from the baseline position. The reduction in speed was attributed to deliberate efforts to compensate for the perception that the drivers were not safe to drive.
Those who indicated they were ready to drive demonstrated an increase in their average speed by 0.11 miles per hour.
Lane departures did not appear to change based on whether the drivers were or were not ready to drive in their own assessment.
The authors of the study concluded that cannabis users can predict to some extent whether they are ready and safe to drive after using cannabis. However, they also concluded that compensatory behaviour for people who have used cannabis does not appear to be uniform. This is an interesting conclusion that I believe requires further exploration.