Here, we define “driving scenarios” as the terrain, driving route, situations encountered, and environmental conditions represented within a simulated drive. If not designed in an evidenced-informed manner, driving scenarios may not allow for a sensitive and reliable measurement of cannabis-related effects on safe driving performance. Driving simulators also provide the ability to introduce graded challenges to test driving abilities under typical and increasingly more difficult driving situations. Therefore, in this paper we offer a framework for developing simulated driving scenarios to test for cannabis-related impairment in a controlled, repeatable, safe way, and offer a prototype driving simulation scenario as an example of this approach. This approach takes into consideration the pharmacological effects of indoor cannabis grow system, the resulting effects on sensory, motor, and cognitive abilities, and how impairments in these abilities could negatively affect driving. Scenarios can be developed to strategically target particular abilities, such as the abilities that are most likely to be influenced by cannabis.
Numerous quantitative data variables can be measured over time and results can be compared between control and experimental groups and among experimental conditions. Driving simulators often also include either a passenger seat or an operator station, thereby allowing for real-time qualitative assessments by trained driving evaluators and/or post-drive evaluations conducted using playback modes. However, the advantages of simulators can only truly be realized for this purpose if the scenarios are designed in ways that, a) target the sensory, motor, and cognitive abilities predicted to be affected by cannabis by, b) design terrain elements, environmental conditions, and events that require these abilities, c) allows meaningful, reliable, and valid outcome measurements to be extracted. For example, cannabis is known to result in reduced speed of processing. Response time can be measured using braking performance. Therefore, introducing events within the driving scenario that require drivers to react quickly, such as a pedestrian entering the roadway or a leading car suddenly braking, will allow researchers to determine whether cannabis use results in poorer driving performance as evidenced through slower braking times.
For many scenario elements, a range of difficulties should be included, since it may be that some measures are only sensitive to cannabis-related effects if the difficulty level is sufficiently high. This graded-difficulty process further highlights the advantages of customized simulation scenarios in that it allows researchers to safely test challenging situations and analyze performance patterns across different difficulty levels within individual participants and across participants. Factors such as route of administration and dosage of THC ,cannabis grow set up should be considered when developing driving simulation scenarios and experimental protocols. For example, the length of the driving scenario should target a time window within which impairment would most likely occur . Impairment of any magnitude in drivers’ sensory, cognitive, or motor abilities can potentially lead to unsafe driving . Michon’s hierarchical model classifies driving behaviors into three distinct levels of performance, namely the “operational level” , “tactical level” , and “strategic level”. Cannabinoids can affect all hierarchical levels of driving behaviours.
For instance, cannabinoids affect various parts of the central nervous system, including the basal ganglia , the hippocampus , and the neocortex. These effects can result in reduced abilities in the domains of visual acuity, coordination, reaction time, concentration, tracking of moving objects, divided attention, sustained attention, critical tracking, working memory, and decision-making ability . As such, simulated driving scenarios should incorporate elements that target each driving behavioural level . For instance, operational performance elements should be implemented to assess drivers with impaired sensory processing and motor coordination abilities, while strategic performance elements may be useful to assess higher-level cognitive impairments such as problems navigating to the desired destination. In order to present graded difficulty levels, increased sensory, motor, or cognitive loads can be introduced, such as by including, for example, low visibility environmental conditions , unexpected events , or multitasking requirements. Below we highlight several representative cannabis-related effects and corresponding scenario elements and driving measures that can be used to help quantify and characterize cannabis-related driving impairments. These effects and associated scenario elements are summarized in Table 1, although the examples listed are not mutually exclusive or exhaustive.