That using cannabis is associated with increased automobile accidents is one of the few cannabis related issues about which there is consensus. Beyond that point of agreement, however, important related issues, such as any association with increased fatal accidents, generate more controversy. What to do about the issue is especially perplexing.
Alcohol impaired driving has been used as the reference point. By comparison, addressing alcohol is much less complicated. Alcohol leaves the body rapidly and has no active metabolites. Blood alcohol levels are easily measured, and the related degree of impairment is well established. When it comes to cannabis, however, none of this holds true.
The situation becomes more complicated when cannabis is combined with alcohol. Well done research studies, using driving simulators, demonstrate that cannabis impaired drivers make adjustments to their driving, such as reducing their speed and increasing the distance between their car and the one in front of them. As their blood alcohol levels are raised, however, these safety compensations are diminished. As a result, mixing a small amount of alcohol and cannabis can cause greater impairment than using larger amounts of either one alone.
This year, after recreational use of cannabis was legalized in California, advertisements by vineyards encouraged wine tasting customers to enjoy the experience more by adding cannabis to the experience. As awareness of the dangers of this interaction increase, these suggestions will hopefully diminish.
With laws being liberalized and cannabis use increasing among adults, THC has become the most frequent intoxicant found in automobile drivers. State legislatures and law enforcement agencies are scrambling for answers. Some have established zero THC levels as a standard, while others set 5 nanograms as the blood level for impairment. The problem is that THC remains in the body long after impairment is gone and there is little evidence supporting the validity of the 5 nanogram level.
The bad news is that right now, there is no solution in sight – yet another reason to lower the barriers to legitimate cannabis research to help address important issues as this one.