cannabis consumption and driving impairment assessment on a closed course

Conditions: Cannabis Smoking; Driving Impaired

Summary: in a true experiment, roughly 300 volunteer participants will smoke active cannabis, a corresponding placebo, or no substance at all (control). next, participants will complete a drive test and then be observed by actual california highway patrol (chp) officers who will attempt to classify participants as impaired or unimpaired. chp officers will evaluate participants in the context of driving (i.e., while following participants in an actual patrol car), as part of a roadside behavioral assessment (i.e., the advanced roadside impaired driving enforcement, or aride, battery, which includes standardized field sobriety tests, or sfsts), and as part of a drug recognition expert (dre) evaluation conducted indoors.

the easing of restrictions on the use of cannabis for recreational purposes presents a new challenge for policing of impaired driving, which is to say driving under the influence of drugs (dui-d), specifically cannabis. in particular, it is not entirely clear how well the tools used by law enforcement officers to detect driving impairment (e.g., behavioral instruments such as the sfsts, as included in the aride battery) work for identifying cannabis-induced driving impairment specifically. while these instruments are designed to help officers identify driving impairment in general (irrespective of cause), prior empirical validation work has almost exclusively involved alcohol-induced impairment. this study will be conducted within a realistic, closed-course driving environment and it seeks to validate the same instruments currently used by law enforcement to detect cannabis-induced driving impairment against a second, independent, behavioral standard for driving impairment: a comprehensive driver evaluation adapted from the same set of driver tests that californians must pass upon application for an original license, or (in certain instances) when referred to the department of motor vehicles (dmv) for evaluation of their ability to safely operate a non-commercial class of motor vehicle (here referred to as the modified driver performance evaluation or mdpe). this study seeks to answer the following research questions: i. how accurately do behavioral assessments used by officers distinguish between drivers impaired by cannabis and drivers not impaired by cannabis? ii. how does cannabis affect real-world (as opposed to simulated) driving performance?

Eligibility criteria:
inclusion criteria: * possessing a valid california driver's license * cannabis use in the past six months * willing and able to abstain from alcohol, cannabis, and other recreational drugs for 24 hours prior to scheduled participation * willing and able to avoid driving and operating heavy machinery for at least four hours after participation * residence within approximately 15 miles of the study site * possessing the capacity to provide informed consent exclusion criteria: * completion of a roadside sobriety test during the previous 12 months * physical or psychological conditions that can be exacerbated by cannabis use, or for which cannabis use is contraindicated * potential presence of cannabis use disorder as assessed by a modified version of the cannabis use disorder identification test * potential presence of substance use disorder as assessed by a modified version of the drug abuse screening test * pregnancy or breastfeeding reported * unwillingness to be transported by taxi * having been convicted of driving under the influence (dui) within five years prior to scheduled participation * parole or probation status * one or more felony convictions on record involving aggressive or dangerous criminal activity * any of the following at the time of the experimental session: breath alcohol content of .01% or greater; positive pregnancy test; cannabis consumption considered unsafe following medical checkup by the study nurse; or driving test behavior considered hazardous by the driving examiner