You are a smoker as well LittleGrizly you know it dulls the senses and that you cannot react as fast in an emergency it can be up to a full second delay, it doesn't have to be the stoned driver causing the situation but having to react to one can be deadly. That is the same for medicine of course, that is why I kinda doubt the numbers in the NYT link Lemur posted, sounds like they are basing a story on a lack of particular data.