Highway Fatalities, Marijuana Legalization and Data

Use of marijuana by drivers pose a risk to other motorists, but poor data collection may hamper our ability to determine the severity of that threat and what can be done to protect other motorists

When Oregon legalized marijuana back in 2014, there were a lot of unknowns. Would it work? Would federal law enforcement suddenly crack down on users in Oregon following state law? Would it cause more crime? Would it lead to more motor vehicle crashes?

In the time since it has been legalized, the sky has not fallen. For drivers in Oregon, the larger problem is knowing just what effect the legalization of marijuana has had on traffic crashes and fatalities. As Mark Twain noted, "There are lies, damned lies, and statistics," and the statistics involving traffic deaths and drugged driving are less than clear.

Fatalities overall have increased

Last year reversed a positive trend of fewer U.S. traffic deaths. As the economy has begun to revive after the recession and gas prices have fallen, a greater number of drivers are driving a larger number of miles. This increases the exposure to potential crashes. Against this backdrop, attempting to tease out the effect of marijuana legalization is difficult.

The Opioid epidemic

In addition to five jurisdictions legalizing marijuana, there is a very significant opioid epidemic that has developed, which means many "drugged driving" crashes may be due to some using opioids, like heroin. Opioids can lead to impairments similar to that of alcohol and may be used in conjunction with other drugs, all of which means even if we have a blood test and it indicates drug use, it may be difficult to determine the degree of impairment due to each drug.

No good test

Marijuana is a particularly difficult drug to measure because it is not water soluble, like alcohol. Alcohol can be shown to dissipate in the blood at a fairly consistent rate, meaning it is possible to estimate blood alcohol content on a timeline when you know the time a reading was obtained.

Marijuana, and its active component, delta-9-tetrahydrocannabinol (THC), is fat-soluble and rapidly collects in the brain and fatty tissue of the body. Because the chemical does not remain in the blood, a blood test may not show any meaningful correlation between the presence of THC and impairment.

Data collection

And this leads to the problem of data collection. In many crashes, a blood test may not be performed. The USA Today reports on the increase nationwide of drugged driving. They produce a graph that shows in 1993 that there were 35,780 fatal crashes and 1,716 were drug-related. At the other end of the graph, it shows in 2015 that there were 32,166 crashes and 6,612 were drug-related.

What it doesn't say is what percentage of fatal crashes had drug tests performed in 1993 vs. 2015. Also relevant would be knowing what drugs the tests were looking for? If you ran a test for alcohol, that test may not have indicated any other drugs, so even with the test, you would have no way of knowing if there were any other drugs in the blood.

Another problem with marijuana is that because THC is fat-soluble, it tends to leach into the blood long after the high has passed and may show up weeks after it had been ingested. Long-term users may exhibit no impairment, yet have positive measurements for THC in their blood.

Why this matters

This matters because without accurate data and a real understanding of what is happening we could enact new laws and develop new highway safety regulations or criminal statutes that would consume a significant amount of the state's resources and have absolutely no effect on improving the safety of the highways or prevent drugged driving crashes.

It also means that if you are involved in a crash with anyone who may be impaired, you want your attorney to thoroughly investigate all of the relevant circumstances of the crash. Drugged driving is not the only form of negligent, impaired behavior, and drivers under the influence of alcohol, distracted by texting, drowsy from lack of sleep and those drivers who are recklessly speeding pose significant threats to all other motorists.

As the head of the nation's top safety investigator notes, human error or negligence is the cause of 94 percent of all crashes.