If there's one thing we've learned in American history, it's that prohibition never works. And yet people continue to push prohibition policies on all sorts of substances, including marijuana and even alcohol. But we're continuing to find proof that those policies are stupid.
Recent research shows that dry county policies are actually not very helpful. A "dry county" is a county in the United States that bans the sale of alcohol. Research shows that dry counties actually have a higher rate of DUI fatalities than "wet" counties. Dry counties have a DUI fatality rate around 6.8 per 10,000 people, while wet counties have a rate of only 1.9 per 10,000. That's about 3.5 times as many drunk driving deaths in counties that ban alcohol sales.
The theory behind this phenomenon is travel. Even if a county bans alcohol, it's highly unlikely that the law will also motivate people to stop drinking. But in order to drink, people need to travel to different counties to do so. So when they need to drive further distances in order to drink, that also increases the chances of them getting into a car accident. This has led researchers to call dry county policies counter productive since they actually increase the risk of the very behavior they're attempting to stop.
This data would seem to suggest how ridiculous prohibitionist policies are. Simply by banning or keeping a substance illegal isn't going to actually prevent people from using it, and there will be consequences to those policies that you don't expect. For alcohol, it's increased DUI deaths in dry counties due to forcing people to drive long distances in order to drink. For marijuana, it's throwing millions of people behind bars for crimes that harm absolutely no one.
In short, prohibition doesn't seem to ever work.