How soon can one drive after consuming alcohol?

Inexperienced marijuana users will often have great difficulty driving and should not attempt it. Research with experienced marijuana users shows that it has no significant effect on their driving. They feel the effects of the marijuana but are able to effectively compensate for them. One example is an article titled "Puff the Dangerous Driver" done by Road and Track in 1980. They set up a driving course and had two groups of people drive it. They gave one group increasing doses of alcohol and the other group increasing doses of marijuana. The group taking alcohol was quickly and obviously unsafe on the course. The group taking marijuana actually did slightly better on the course when stoned on marijuana. This is not because marijuana improves performance, but simply shows that it doesn't diminish performance so that they got better with practice.