An anonymous reader writes: WFXS Fox 55 reports, "The legalization of marijuana is an idea that is gaining momentum in the United States, but there may be a dark side to pot becoming more commonplace ... Fatal crashes involving marijuana use tripled during the previous decade, fueling some of the overall increase in drugged-driving traffic deaths ... "Currently, one of nine drivers involved in fatal crashes would test positive for marijuana," said co-author Dr. Guohua Li, director of the Center for Injury Epidemiology and Prevention at Columbia. "If this trend continues, in five or six years non-alcohol drugs will overtake alcohol to become the most common substance involved in deaths related to impaired driving." ... Alcohol contributed to about the same percentage of traffic fatalities throughout the decade, about 40 percent, Li said. ... Drugged driving accounted for more than 28 percent of traffic deaths in 2010, up from more than 16 percent in 1999. Marijuana proved to be the main drug involved in the increase, contributing to 12 percent of 2010 crashes compared with 4 percent in 1999. The study authors also noted that the combined use of alcohol and marijuana dramatically increases a driver's risk of death. "If a driver is under the influence of alcohol, their risk of a fatal crash is 13 times higher than the risk of the driver who is not under the influence of alcohol," Li said. "But if the driver is under the influence of both alcohol and marijuana, their risk increases to 24 times that of a sober person.""