In the video below, Motoring TV host Jim Kenzie looks at people who drive under the influence of Marijuana.
Estimates are as many as 30% of young drivers have driven while high. To add to the problem, there is no quick way to tell if a motorist is impaired due to the effects of marijuana. Blood or urine tests are the only reliable methods, unlike impairment due to alcohol which can easily be determined from a breathalyser.
Some people say being high makes you a more cautious driver whereas alcohol causes you to be more aggressive. Either way, any form of impairment is dangerous (including fatigue) and you should always call a cab when faced with this situation.
http://motoringtv.com/video/motoring-tv-2014-episode-18-kenzies-korner-driving-while-high/