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Does Marijuana Legalization Lead to Increased Impaired Driving?


According to the Insurance Institute for Highway Safety (IIHS), crash data suggests that the states that legalize marijuana have had nearly a ten (10%) percent increase in auto accidents compared to the states that restrict marijuana or use the substance for medicinal uses only. According to David Harkey, President of the IIHS, “there is a definite increase in crash risk that is associated with the legalized recreational use of marijuana.” However, Mr. Harkey also tempered his remarks by cautioning that the study results indicate only a correlation between marijuana legalization and a higher number of crashes, and says more research would be necessary to determine whether marijuana use caused the increase.

Complicating the issue of whether marijuana use caused or contributed to the crashes is the issue of THC. THC is the psychoactive component of cannabis and can clearly affect driving. However, because of the nature of THC, the level of driver impairment is difficult to evaluate.

Unlike alcohol, the presence of THC in the body does not necessarily mean that an individual is impaired, and a higher level of marijuana use does not necessarily mean greater impairment. Different forms of THC-containing products affect the body in different ways. That makes it more difficult for researchers and law enforcement alike to determine impairment levels. Therefore, determining Cannabis impairment is not as easy as alcohol impairment, such as checking one’s blood alcohol content (“BAC”).

Currently, ten (10) states and the District of Columbia (and the entire country of Canada) have allowed recreational marijuana use. Maryland is not one of them, as Maryland is one of the twenty-three (23) states who allow Marijuana for medicinal purposes only. Further, based upon the IIHS study there are some conclusions that may be inferred:

  1. As more states legalize recreational marijuana, more effort will be needed to determine how best to prevent impaired driving crashes;
  2. As more states legalize recreational marijuana, if the current statistics are valid, there will be more crashes, and ultimately, injuries on our roads; and
  3. As long as the insurance industry (the IIHS) relies on the aforesaid statistics, drivers in states that legalize marijuana will be paying higher insurance premiums commensurate with the higher rate of car crashes, accidents and injuries.

If you or a loved one has been involved in an accident where the driver was under the influence of marijuana contact the experienced attorneys at Shapiro Zwanetz & Lake today!