University of Iowa studies impact of marijuana on driving

http://www.eurekalert.org/pub_releases/2015-06/uoi-uoi062315.php

Public Release: 23-Jun-2015
University of Iowa studies impact of marijuana on driving

First-of-its-kind study at University of Iowa's National Advanced Simulator shows how marijuana and marijuana with alcohol impacts driving

University of Iowa

A new study conducted at the University of Iowa's National Advanced Driving Simulator has found drivers who use alcohol and marijuana together weave more on a virtual roadway than drivers who use either substance independently. However, the cocktail of alcohol and marijuana does not double the effect of the impairment.

"What we saw was an additive effect, not a synergistic effect, when we put them together," said Tim Brown, associate research scientist at NADS and corresponding author of the study. "You get what you expect if you take alcohol and cannabis and merge them together."

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To date, medical marijuana is legal in 23 states and the District of Columbia while marijuana has been approved for recreational use in four states and D.C. Since legalizing medical marijuana, Colorado has reported an increase in driving under the influence of cannabis cases and fatal motor vehicle crashes with cannabis-only positive drivers while states without legalized marijuana have experienced no significant change in cannabis-related crashes.

Last year, the National Highway Traffic Safety Administration's Roadside Survey of Alcohol and Drug Use by Drivers found the number of drivers with alcohol in their system has declined by nearly one-third since 2007. However, that same survey found the number of weekend nighttime drivers with evidence of drugs in their system climbed from 16.3 percent in 2007 to 20 percent in 2014. The number of drivers with marijuana in their system grew by nearly 50 percent.

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