A recent U.S. study found that states with Medical Marijuana had an almost ten-percent decline in Traffic Fatalities.
Don't take my word, Google it yourself
http://www.google.ca/search?client=safari&rls=en&q=MARIJUANA+REDUCES+TRAFFIC+FATALITIES+9%25&ie=UTF-8&oe=UTF-8&gfe_rd=cr&ei=DNo8WI7dPI2EiAPDnq-IBQ

If it were anything else, they'd be aggressively passing legislation "to save lives".
One often hears that something "is worth it if even one life is saved".
Nine-percent is a lot of lives saved by Cannabis !