This is very relevant with respect to recommendations about driving. The current lower-risk cannabis-smoking guidelines that have been put out by Fischer and the Canadian Journal of Public Health suggest that people who use cannabis not drive for at least three to four hours after use. Probably it should be longer than that for oral use—up to six hours—and some have suggested that if the patient experiences euphoria from the cannabis, which suggests a very high drug level, that they not drive for at least eight hours.
On May 1st, 2014. See this statement in context.