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A comment on Stoned drivers are safer than drunk ones, new federal data show. Parent comment

Re:Stoned drivers are safer than drunk ones, new federal dat... by mirimir on Monday May 16, 2016 @11:48AM (#11707071)
Yes, this is a key problem with the study. THC metabolites are cleared very slowly. Testing positive indicates that you used marijuana within a week or two. It doesn't mean that you're stoned.

For alcohol, a comparable test might look at long-term changes in liver biochemistry associated with alcohol consumption. In that case, there probably wouldn't be any correlation with accident rates.

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Re:Stoned drivers are safer than drunk ones, new federal dat... by maxerickson on Monday May 16, 2016 @11:53AM (#11707115)
Blood tests can directly measure THC. The article seems to be talking about such tests.

The problem is that there is not a well established mapping between THC levels and impairment. It isn't even clear if such a mapping can be done.

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Re:Stoned drivers are safer than drunk ones, new federal dat... by mirimir on Monday May 16, 2016 @12:24PM (#11707380)
Maybe there's a key distinction between THC levels in the blood and bioavailable THC. THC is extremely lipophilic, so it might get trapped for degradation.
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