New study partially funded by the federal government finds that alcohol impairs drivers much worse than marijuana. In a sophisticated driving simulator, 19 adults were tested with marijuana, alcohol, and placebo in a 45 minute drive to discover the way that drivers become impaired after using such drugs. Alcohol consistently raised the number of times drivers left the lane and weaved, while marijuanas only downfall showed as creating tunnel vision for certain drivers.
Researchers said alcohol "significantly increased lane departures/minimum and maximum lateral acceleration; these measures were not sensitive to cannabis." Researchers also concluded Cannabis-influenced drivers "may attempt to drive more cautiously to compensate for impairing effects, whereas alcohol-influenced drivers often underestimate their impairment and take more risk."
Original article: http://www.cnn.com/2015/06/24/politics/marijuana-study-drivers-impact/