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Updated: October 28, 2016
The proportion of drivers that test positive for marijuana and other drugs is on the rise on our nation’s roadways . While the legality of marijuana is being debated at the State level, it’s not clearly understood how marijuana impacts a person’s ability to drive. Specific marijuana concentration levels cannot be reliably equated with a specific degree of driver impairment. With the exception of alcohol, little has been done to measure the effects of marijuana and other drugs on driving safety.
Gaining on more information about the impact of marijuana on driving was the motivation of the research study that was conducted at NADS and the University of Iowa. The study looks at six combinations of marijuana and alcohol to replicate the drug levels that are commonly found in drivers on the road. The study was jointly sponsored by the National Institute of Drug Abuse (NIDA), the Office of the National Drug Control Policy and the National Highway Traffic Safety Administration (NHTSA).
The clinical trial was conducted on the world renowned NADS-1 driving simulator. Nineteen participants drove a typical passenger sedan in a nighttime driving environment that exposed them to urban, suburban, interstate and rural driving situations over a 45 minute drive. This nighttime driving has previously been used for a range of studies involving alcohol impairment, distraction and drowsiness. The primary outcome measure was driving performance as measured by speed, lane position, steering wheel position, reaction time, headway to lead vehicle and eye tracking.
Prior to the start of the study, specific improvements were made to the NADS facility to support the safe storage, delivery and consumption of cannabis to meet FDA and DEA requirements. NADS staff and faculty also underwent training to gain approval from regulatory agencies; more specifically, Dr. Gary Gaffney, the lead principal investigator, also applied for and obtained a DEA license.
The study found that participants who consumed only alcohol weaved more than those who consumed only vaporized cannabis . More results are in the process of being made public by the sponsoring agencies.
With the trending legalization of marijuana, there has been a significant interest in the public and media. These include coverage by USA Today, Time.com, CNN, PBS Newshour, and Iowa Public Radio.
