Skip to main content
An image of one of our staff members sitting at 3 computer screens using a driving simulator.  His hands are on a driving wheel attached to the simulator.


As medical cannabis becomes more readily available, it is imperative that any risks relating to driving are clarified via thorough research
Our research on medical cannabis and driving is contributing to the ongoing policy debate regarding issues such as safety, impairment and detection.

Our Research

Exploring the effects of THC and CBD on simulated driving (completed, 2019)


This study compared the effects of standard high-THC cannabis, balanced THC/CBD cannabis, and placebo cannabis on simulated driving and cognitive performance. In a randomized, double-blind, crossover design, 14 healthy volunteers with a history of light cannabis use attended 3 outpatient experimental test sessions in which simulated driving and cognitive performance were assessed.

Results: The type of impairment seen with high THC cannabis involving greater lane-weaving. However, on other measures intoxicated participants were somewhat safer, tending to leave a larger gap between them and the car in front compared and showing no tendency to speed.

Contrary to prediction, the study found that the addition of CBD did not reduce feelings of intoxication, nor did it lessen driving impairment compared with standard high-THC cannabis. In some circumstances, the study found that CBD exacerbated THC-induced impairment.

This was a collaboration between The Lambert Initiative at the University of Sydney, Royal Prince Alfred Hospital and Tilray.

Chief Investigators: Professor Iain McGregor (Lambert Initiative, University of Sydney)

Project Coordinator: Thomas Arkell (Lambert Initiative, University of Sydney)

Vaporised medicinal cannabis and driving ability: an on-road study in healthy volunteers

Experimental studies indicate that cannabis causes dose-dependent impairment in driving performance and associated cognitive function, however these studies have only considered the effects of the main intoxicating component of cannabis, THC. Here we will examine in a four way crossover design trial, whether vaporized medicinal cannabis containing a 1:1 ratio of THC and CBD impairs driving in the same way as cannabis containing an equivalent amount of THC with no CBD, as well as effects of vaporised CBD only (no THC) on performance. The novel study will examine real-world driving performance at various time points following consumption and examine driving in both urban and highway environments.

This is a collaboration between The Lambert Initiative at the University of Sydney, Maastricht University and Bedrocan International.

Chief Investigators: Professor Jan Ramaekers (Maastricht University)

Project Coordinator: Thomas Arkell (Lambert Initiative, University of Sydney)