Drivin' That Train, High on Mary Jane

The states are in a tizzy these days trying to determine the proper amount of TCH one can have in one's system before one is considered impaired.

Perhaps the most interesting part of the discussion is that no one is questioning the basic assumption: does THC impair one’s driving abilities? The levels allowed are being determined without any evidence that there is a causal relationship between unsafe driving and marijuana consumption.

Actuarial tables and state driving statistics indicate that marijuana smokers are safer than average drivers. This could be the result of one of two alternatives: either people who tend to be safer drivers are more likely to smoke marijuana than those people who tend not so safely; or smoking marijuana tends to make one a safer driver. The most relevant existing piece of data informing that question is that states that have adopted a medical marijuana program have seen an average reduction of traffic fatalities of 11%. The implication being that an increased percentage of marijuana smokers on the road creates safer conditions.

Why, then, are the states rushing to find acceptable TCH levels above which one is considered impaired? And how do they determine that level?

The “why” is more complicated; the “how” is easier: they don’t. There has been no causal relationship demonstrated between marijuana consumption and impaired driving. The assumption of impairment is based on a number of factors: people with a limited experience with cannabis tend to equate a cannabis high with alcoholic inebriation, which, conversely, most of them have experienced, and they have a hard time understanding the differences; a large anti-marijuana prejudice still exists which inclines people to believe the worst about the effects of marijuana without having actual data to back those beliefs up (the drug war under a new guise); and most commonly, people conflate laboratory results with actual driving conditions, making the assumption that lab results directly translate to driving performance.

In other words, the laws against driving while stoned are all based on unproved assumptions that are, most likely, wrong. The basic assumption is that decreased reaction time leads to unsafe drivers; and that is the basic, untested assumption. As mentioned, the only real-time test we have of that situation is in states which have legalized medical marijuana, and in those state fatalities, at least, have been reduced.

There is, though, a parallel situation with age. Laboratory tests—not to mention experience—conclusively demonstrate that one’s reaction times slow considerably as one ages; yet, paradoxically, people become safer drivers as they age. Experience helps, yes, especially the experience to compensate for diminishing skills, something marijuana smokers seem to understand inherently. Perhaps the experience comes quickly for them.

I suppose it was too much to hope for that the entire drug war should be over with in one fell swoop.