As marijuana becomes legal in more places in the United States, experts have reported that they fear it could lead to a rise in car accidents. It’s a clear concern that people could be driving while under the influence of marijuana more frequently if the drug is legalized. Where it already is legal, states like Colorado and Washington, research on the topic could make a major difference in further legalization throughout the U.S.

Research on the topic is surprisingly inconclusive. In Washington, it’s true that there was close to a 25-percent rise in the number of drivers testing positive for marijuana within the first year of the drug’s legalization. However, the number of crashes and fatalities was not an equivalent increase. Some people claim that driving while high doesn’t significantly change the risk of being in a car accident; others believe that the number of fatal car accidents involving drivers who were high has increased by close to threefold over the last 10 years.

Oregon is likely to legalize marijuana in November 2014, but it has said that it’s important to monitor traffic. Their concern is trafficking the drug; right now, it’s not legal to take the drug out of Washington or Colorado without a medical prescription.

The executive director of Governors Highway Safety Association has said that the legalization of the drug is a wake-up call. It points out how little is known about marijuana-impaired driving and whether it could be a large or very small problem. Any kind of impairment on the roads is a problem, whether or not people can agree on how much marijuana is enough to be impaired.

Source: International Business Times, “Legalizing Marijuana Could Mean More Traffic Accidents, Experts Fear, But Research Unclear” Philip Ross, Sep. 02, 2014