An amazing study authored by professors D. Mark Anderson (University of Montana) and Daniel Rees (University of Colorado) shows that traffic deaths have been reduced in states where medical marijuana is legalized.
According to their findings, the use of medical marijuana has caused traffic related fatalities to fall by nearly nine percent in states that have legalized medical marijuana (via The Truth About Cars).
The study notes that this is equal to the effect raising the drinking age to 21 had on reducing traffic fatalities.
One key factor is the reduction in alcohol consumption. The study finds that there is a direct correlation between the use of marijuana and a reduction in beer sales, especially in the younger folks aged 20-29.
A drop in beer sales supports the theory that marijuana can act as a substitute for liquor.
The study also finds that marijuana has the inverse effect that alcohol does on drivers. Drivers under the influence of alcohol tend to make rash decisions and risky moves, whereas those under the influence of marijuana tend to slow down, make safer choices, and increase following distances.
A 1983 study by the US National Highway Transportation Safety Administration (NHTSA) concluded that the only significant affect of cannabis use was slower driving – arguably a positive effect of driving high. A comprehensive 1992 NHTSA study revealed that pot is rarely involved in driving accidents, except when combined with alcohol. The study concluded that “the THC-only drivers had an [accident]responsibility rate below that of the drug free drivers.” This study was buried for six years and not released until 1998. A massive 1998 study by the University of Adelaide and Transport South Australia examined blood samples from drivers involved in 2,500 accidents. It found that drivers with only cannabis in their systems were slightly less likely to cause accidents than those without.