Increases in marijuana, opioid use are clear; determining what’s impaired driving is not so easy

Eli Pace

As marijuana use becomes more prevalent and the nation struggles with a rising opioid epidemic, the Governors Highway Safety Association (GHSA) recently released a new report examining the impacts of drugged driving. Issued May 31, the report and its conclusions are not all that surprising, but some of the ideas the agency has for addressing the problems might be.

The researchers relied heavily on statistics complied by the Fatality Analysis Reporting System, which remains the best source for this kind of information but comes with "substantial limitations," according to the GHSA. For example, testing rates of crashes with fatally injured drivers vary widely from one state to another, ranging from as high as 96 percent to as low as 2 percent.

The new report comes as marijuana and opioid use across the U.S. are on the rise compared to previous decades. Recreational marijuana is now allowed in nine states and medical marijuana has been legalized in 29 states and Washington, D.C.

Additionally, an estimated 115 people died daily from opioid overdoses in the U.S. in 2016, and prescriptions for drugs like oxycodone, hydrocodone, codeine, morphine and many others have gone from 107 million in 1992 to 277 million in 2012 before dipping back down slightly in 2016.

With the legalization of marijuana has come more options. The drug can now be smoked, eaten, absorbed through the skin, inhaled as a vapor or dabbed, all of which deliver different potencies of THC, the active chemical in marijuana, and release it into the body on different time tables.

 

Adding to the confusion, there is no way to accurately measure the amount of marijuana someone has used by breath, and any tests for pot must done with blood, urine or saliva. But those tests are problematic too, because marijuana metabolites, which do not cause impairment, can remain in someone's system for weeks, and even the tests that only measure THC fail to take into account the amount of THC in someone's system isn't always directly tied to a corresponding level of impairment.

Despite all the limitations, the report says the following conclusions about fatally injured drivers are fully supported:

• Drug presence probably increased slightly from 2015 to 2016.

• Alcohol presence remained about the same in 2016 as in 2015.

• Many drivers combine more than one drug or drugs and alcohol.

• Drug presence increased substantially from 2006 to 2016.

Colorado and Washington, the first two states to allow recreational marijuana use, have both shown upticks in the number of drivers operating vehicles after using marijuana. In roadside surveys conducted immediately before and after legal sales began in July 2014, Washington saw a spike in the number of drivers who tested positive for THC. In Colorado, the number of traffic fatalities in which a driver tested positive for THC increased in the years after recreational marijuana was legalized, jumping from 18 in 2013 to 77 in 2016.

Numerous studies have shown marijuana can hamper essential driving skills, like reducing one's vigilance, causing drowsiness or altering perceptions of time and distance. Marijuana also can slow reaction times, reduce coordination, affect one's balance and hinder his or her ability to track lanes.

But those effects aren't universal because "chronic marijuana users may not be impaired even with high levels of marijuana in their bodies," according to the GHSA. Furthermore, marijuana's relationship to crashes is even less clear, especially since the testing has not yet caught up to the rise in its use.

"The most supportable conclusions are that marijuana has caused or contributed to some crashes; that it can, but need not necessarily, increase crash risk in a driver; and that the best overall estimate of marijuana's effect on crash risk in general is an increase of 25-35 percent, or a factor of 1.25-1.35," the report states.

The report comes as many states are seeking strategies to combat impaired driving from marijuana and opioids, which most state highway safety offices actually pegged as equal to or worse than drunk driving.

While the report highlights the challenges of accurately measuring drug-related driving statistic — including the lack of a nationally accepted testing method for drug impairment, the large number of drugs to test for and the differences in their effects between different drugs and drivers — it does provide some recommendations for curbing the problem.

Top among them is a GHSA recommendation to add anti-drugged driving messaging, specifically related to marijuana and prescriptions, to public education campaigns, much like the Colorado Department of Transportation's Cannabis Conversation, launched last February.

Other ideas include more training for law enforcement, judges and prosecutors who handle drug-related DUI cases; requiring blood tests for all drivers suspected of using drugs; testing all drivers involved in fatal collisions; considering "at least a test" of devices that analyze oral fluids; and "closely" following the development of a marijuana breathalyzer and putting it into use as soon as it becomes available.