Rapid review of experimental studies on alcohol and cannabis use and simulated driving behaviour: What can we learn about study methods?

Driving under the influence of alcohol and cannabis, either alone or in combination, remains a significant public health concern due to the increased risk of fatal or serious injury crashes. Experimental studies using driving simulators provide a safe and controlled method for examining the effects of these substances on driving performance. However, limited research has critically analysed commonly used methodologies, and variations across studies complicate comparisons and the interpretation of findings. This rapid review synthesises methodological considerations in experimental simulator studies published in the past five years, focusing on research design, participant selection, substance administration, simulated driving hardware, and outcome measures. Through systematic database searches, we identified 3,698 publications that assessed the effects of alcohol, cannabis, or their combination on simulated driving. Following full-text review, a total of 54 studies were deemed eligible for narrative synthesis. High quality research designs (within-subject crossover designs) were feasible but were not always used. Cannabis administration methods varied markedly across studies relative to alcohol and had important implications for factors such as administration timing. For alcohol, standardised and evidence-based protocols for placebo preparation were lacking. Driving simulators differed in fidelity, ranging from full-cab motion-based setups to PC-based systems with varying fields of view. The most commonly assessed driving performance measures were standard deviation of lane position (SDLP) and speed control. Additionally, few studies examined the combined effects of alcohol and cannabis, or accounted for factors such as cross-tolerance, individual differences in substance use history, or simulator sickness. This review highlights the need for standardisation in experimental simulator research on substance-impaired driving. Establishing methodological guidelines could improve the reliability and generalisability of findings, thereby improving the overall quality of experimental research in this area.