NATIONAL HIGHWAY TRAFFIC SAFETY ADMINISTRATION — A new federal study shows that drivers who have used pot are just as likely to get into a crash as sober drivers. The study was performed by the National Highway Traffic Safety Administration (NHTSA) in Virginia and compared more than 3,000 drivers in the area who were involved in an accident with over 6,000 control drivers who were not in an accident.
The NHTSA’s study found that after adjusting for demographic factors, as well as alcohol use, marijuana users were not at a higher risk of crashing than sober drivers. The study also found that drivers were at a much higher risk of crashing after consuming alcohol than marijuana.
The crash risk study is the first large-scale study of its kind in the United States that includes drugs other than alcohol. The research team responded to crashes in Virginia over a 20-month period, seven days a week 24-hours a day. After a driver involved in a crash was added to the data the researchers returned to the site of the crash on the same day of the week, at the same time, and traveling in the same direction to get another driver not involved in a crash that could balance out the research.
The report found that nearly 8 percent of drivers who crashed had marijuana in their system. Compare that with nearly 6 percent of the control drivers (those who didn’t crash) who also had marijuana in their system. Demographic factors like age, sex, gender, and ethnicity were found to account for an increase in crash risk as well. The study also found that if a driver with pot in their system was also a young male; their crash risk may have been related to their age and gender rather than their use of pot.
Gordon Trowbridge, spokesman for the NHTSA, told The Seattle Times that there are many studies like these for alcohol and marijuana based studies are few. “We have decades of data on alcohol…and it’s easier to interpret. It has less complex effects than marijuana,” Trowbridge told the Seattle Times.
Washington state has a strict 5ng per se Marijuana limit. It would be helpful if a driver’s drug concentration in blood were directly related to a specific degree of driving impairment. However, the relationship between drug concentrations and physiological and behavioral impairment is complex. With the exception of ethanol, few experimental data are available correlating drug concentrations in blood to driving impairment.
The NHTSA plans to do more studies like this one in the future.The full study from the National Highway Traffic Administration can be found here full study: http://kimabim.s3.amazonaws.com/812117-Drug_and_Alcohol_Crash_Risk.pdf