As marijuana use becomes more accepted publicly and more states introduce laws allowing the medicinal or recreational use of the drug, the issue of driving while stoned has become topical.
CNN tested the driving skills of three people under the influence of cannabis and found that the volunteers' driving was fine after smoking small amounts of the drug, but that driving skills became increasingly impaired as the subjects smoked more weed.
In Washington state, where voters approved a measure to legalize recreational marijuana use last November, a "heavy" marijuana smoker, a "weekend" user and an "occasional" fan of the drug were taken to a closed driving course and given a driving test after getting high.
The legal limit for marijuana in the bloodstream in Washington is five nanograms of tetrahydrocannabinol, or THC, the active compound in marijuana.
Each driver was given a driving assessment before getting high. However, the "heavy" smoker came to the CNN test having already gotten high earlier in the day. Her blood test showed she was at more than three times the legal limit at 15.9 nanograms.
Cascade Driving School instructor Mike Jackson was in the car with each of the test subjects. He said that even though the heavy smoker tested to three times the legal limit for the pretest, her driving was fine.
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After the pretest, the drivers were asked to smoke 0.3 grams of marijuana and then get behind the wheel. After smoking 0.3 grams the heavy user said she felt fine while the other two volunteers said they felt buzzed and relaxed. Though a blood test showed that she was at seven times the legal limit, the heavy user's driving was still acceptable, Jackson said. The other two drivers also drove acceptably on the test course, even though their blood tests showed they were well above the legal limit.
CNN asked the volunteers to smoke two more times and tested their driving skills after the subjects smoked 0.9 grams of marijuana. Drivers showed signs of confusion and impaired driving, with the occasional and weekend user, who have lower tolerance to the drug, found to be too stoned to drive.
However, even though the heavy smoker had smoked before the test and then nearly a gram of marijuana during the test, the driving instructor and the sherif's officer on the scene did not determine her driving to be unsafe.
She was asked to smoke another 0.3 grams, making her total for the test 1.4 grams. After smoking so much, she was clearly impaired and the officials involved said it she was clearly in no condition to be driving.
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