What can a lane departure tell you about alprazolam in a driving case?

The study controlled the drug and the drive

Stone and colleagues compared an immediate-release alprazolam dose with placebo in a double-blind simulator study. Nineteen participants were included in the analysis. Researchers separated driving segments and measured lateral position and lane departures rather than treating the full simulated drive as one observation.

The road segment mattered

The study found greater lane-position variability under alprazolam in several segments. On a relatively straight urban segment, for example, the standard deviation of lane position was about 26 cm after alprazolam and 19 cm after placebo. That measure describes how much the vehicle moved laterally around its average position. It differs from a count of times the vehicle crossed a lane boundary.

Connect the observation to the evidence

For an actual drive, identify the roadway geometry, lane markings and traffic demands shown in the footage. Compare the timing of the observations with the medication history and any specimen collection. The experiment supports a plausible relationship under controlled conditions. Its small sample and scripted driving tasks leave the cause of an individual lane departure unresolved.

Source paper

Stone et al., Frontiers in Psychology (2015) · Full text