You are either quite confused or you are just employing a pathetic strawman argument. The correlation is between legalization of marijuana or medical marijuana and reduced traffic fatalities. The research supports this pretty conclusively and you have offered nothing to dispute it.
The premise of the thread is not about driving under the influence. Look at the title.
The fact that alcohol is more likely to be consumed outside the home is not the proven reason for the difference in fatalities. It's effects just can't be ruled out but it's not relevant to the premise, unless you can establish that legalization is going to drastically change usage habits. You have provided nothing on that. However, there is plenty of research to support that marijuana causes a less intense impairment and that the user is more aware of impairment. It more than likely is a major factor in the difference.
Pinhead logic......its laughable....you know when desh agrees with you, you must be fucked up.