With marijuana for medical and recreational use gaining increasing acceptance and popularity across the nation, the social issues this raises have been examined from many sides. What about impairment in the workplace? What course of action should employers take? What are the health risks of extended use? How does pot intoxication compare with alcohol? How does this shift impact drug testing?
Now one concern thoroughly explored on the alcohol side is coming under increasing scrutiny for pot users: what are the effects (and threats) on driving and driving safety from marijuana? And furthermore, what is the effect of both on a driver?
New studies are examining the issue from various angles: statistics, anecdotal, and testing of reflexes and blood content. One aim of these studies is to establish consistent legal and law enforcement guidelines for permitted thresholds of THC (the active chemical in pot) in drivers, aimed at developing drug testing guidelines like those used for alcohol at police traffic stops. It took decades to arrive at the widely-accepted 0.08% Blood Alcohol Content (BAC) as the legal limit for driving in many states. Finding such a limit for THC may be much more problematic.
Just as alcohol can affect individuals differently based on sex, body type, consumption, and rate of metabolizing, marijuana has a considerable range of impact.
A study by the National Institute on Drug Abuse was conducted at the University of Iowa, on a virtual reality driving simulator. Much like professional flight simulators, the system in Iowa uses variable motion and high-end computer graphics to provide a realistic visual, auditory, and visceral experience of driving. It tested the impact of alcohol, THC, and both on driving ability, with placebo control groups as a comparison.
Here are some of the findings:
- Pot and alcohol users both had significant decline in driving ability and increase in errors such as failure to stay in lanes.
- Experienced pot users had fewer effects on their driving than novices at the same THC blood levels.
- Drivers intoxicated on THC were more aware of their limitations than those on alcohol, and took measures like driving slower to compensate.
- Drivers on both pot and alcohol at the same time had higher decline of driving ability and greater loss in judgment than those on either substance alone.
While the study offered no firm recommendations on specific levels of THC, there were other questions raised that may impact decisions on drug testing. Heavier users of pot had THC in their systems for several weeks, negatively impacting reaction and judgment test during that time. And pot smoked at the same time as consuming alcohol seemed to delay the consumer’s recognition of their impairment, making the combination more dangerous.
Coming to some sort of consensus of how to treat drivers with THC in their system is becoming increasingly urgent: driving drunk is on the decline, while driving high is on the upswing. The National Highway Traffic Safety Administration reported a limited survey of drivers that showed 8.3% with alcohol in their bodies and 12.6% with THC. That’s an increase of almost 50% for pot-smoking drivers since 2007.
Photo by University of Iowa National Advanced Driving Simulator,
