Please fully read and understand the resource you linked > Experienced smokers who drive on a set course show almost no functional impairment under the influen

Please fully read and understand the resource you linked > Experienced smokers who drive on a set course show almost no functional impairment under the influence of marijuana, except when it is combined with alcohol. And the conclusion that the lack of functional impairment is due to increased awareness of impairment is merely speculation and is not based on any empirical result.