The RSA commissioned the research amongst a sample of 1,000 people, and 22 percent said they had been a passenger in a car driven by someone under the influence of such drugs.
Almost half of the sample said they have themselves used recreational drugs in the past.
Almost four in five respondents believe that driving under the influence of such drugs is 'very unacceptable'.
The RSA is screening a new TV advertisement aimed at dissuading young motorists from driving while using drugs.
