Cannabis and highway carnage: hard truths

Posted on May 18th, 2018 by Bill Weinberg and tagged , , , , , , .

trafficA deadly five-car pile-up on a Bay Area freeway brings into sharp focus the questions around cannabis use and road safety. Media exploitation of such carnage as propaganda against legalization, however, is missing some critical points.

The five-vehicle collision on Interstate 880 in Fremont the night of May 15 was truly horrific. Among the three dead are two sisters, aged 14 and nine. Five others were hospitalized, including a youth who is said to be in critical condition. Motorist Dang Nguyen Hai Tran was arrested at the scene—on suspicion of driving under the influence of cannabis.

In the report on local KPIX, the newscaster intoned with damning resonance: "The CHP say they have evidence the 21-year-old driver who caused a five-car pile-up in Fremont was stoned... The crash is highlighting one of the biggest concerns about legalized pot."  Stanford University's Dr. Keith Humphreys is quoted as saying, "Your motor coordination is worse... people who are intoxicated on cannabis, like people who are intoxicated on alcohol, make much worse drivers." A classmate of one of the slain girls poignantly tells the camera, "How a person can be so careless to take another person's life away over a drug, it really is heart-breaking." (The report does mention that all three of those killed were not wearing their seatbelts.)

A more distanced analysis following the ghastly incident is provided by reporter Patrick May in the San Jose Mercury News. Like the KPIX account, he cites statistics from the California Highway Patrol's Golden Gate District indicating that if trends continue, the nine counties that make up the San Francisco Bay Area could see a 70% rise in marijuana DUI arrests this year over last. DUI arrests solely for cannabis in 2017 totaled 197. For January through mid-April of 2018 they are already up to 87.

But May acknowledges: "What constitutes a 'marijuana-related' accident is still wrapped up in controversy."

May notes that in 2016, four years after Colorado legalized cannabis, then Libertarian presidential candidate Gary Johnson said "marijuana-related" traffic deaths and hospital visits in the state had "not significantly" increased since legalization. But according to FactCheck, Johnson's claim did not check out. Official stats showed that "marijuana-related" traffic deaths in Colorado increased 154% between 2006 and 2014. Emergency room visits deemed to be "likely related" to cannabis increased by 775 from 2011 to 2014.

However, it is something of an open question how meaningful these figures are in terms of causality. As FactCheck stated, "Unlike alcohol...testing positive for marijuana doesn’t necessarily mean a person is under the influence of the drug at the time of the traffic accident." That's because THC stays in your body a lot longer than alcohol does—well after the effects wear off.

In May 2016, according to FactCheck, the American Automobile Association conducted an analysis of "marijuana-related" fatalities in Washington state—which also voted to legalize in 2012. It found (PDF) that around twice as many "fatal-crash-involved drivers" had THC in their system in 2014 compared with previous years.

But the AAA report cautioned that testing positive for THC doesn't mean the driver was impaired or at fault for the crash. The report added that many THC-positive motorists also had alcohol and other drugs in their system, "which in some cases likely contributed more significantly to the crash than did the THC."

By way of illustration, May cited a November 2017 crash in Vermont that killed five teens. A toxicology report for the man accused of causing the crash indicated that he had THC, fentanyl and a sedative in his blood. Authorities acknowledged that the sedative, Midazolam, causes "significant impairment in driving and psychomotor abilities." 

May is to be applauded for clearing the air at what is certainly a fraught moment n the Bay Area. The entire question of "marijuana-impaired driving" tends to be misunderstood. For example, it is true that Colorado has seen an increase in overall road fatalities since legalization in 2012, as well as an increase in cannabis-related driving offenses. But the increase in road fatalities is consistent with the trend across the US—and likely related to more motorists on the highways due to low oil prices. Note that the world oil slump began in 2014—just in time to lubricate bad propaganda for cannabis legalization. In 2009, when the oil price spike set off by the Iraq war was at its peak, highway fatalities coast to coast dropped to 1960s levels, as the Associated Press noted at the time.

A 2011 study by the University of Colorado at Denver (from before the oil slump) found a reduction in traffic fatalities in states that had legalized medical marijuana. A probable explanation is that folks had been turning to legal cannabis instead of alcohol—which impairs driving far more dramatically.

And contrary to impressions gleaned from media sound-bites, the difference between cannabis and alcohol in terms of impact on driving is quantifiable. A 2015 study by the National Highway Traffic Safety Administration (NHTSA) found that drivers high on pot are not nearly as impaired as drunk drivers. As the Washington Post summed up the findings: "After adjusting for age, gender, race and alcohol use, drivers who tested positive for marijuana were no more likely to crash than who had not used any drugs or alcohol prior to driving."

Paul Armentano, deputy director at the National Organization for the Reform of Marijuana Laws (NORML), has emphasized the contrast with alcohol: "We don't have a consensus as to what levels of THC are consistently correlated with behavioral impairment."

So let's see what facts emerge from the investigation into this week's carnage on the Nimitz Freeway. Certainly, the cannabis community should emphasize responsible use. Motorists who use cannabis—like all motorists—must take their state of mind and body while behind the wheel with the utmost seriousness. But let's also strive for a little perspective amid the media rush to blame cannabis for traffic fatalities in simplistic terms.

Cross-post to Cannabis Now

Karin Dalziel via Flickr


Deconstructing cannabis DUI data

Global Ganja Report's picture "There are 2 major flaws in marijuana DUI data post legalization. First, science supports that the mere presence of THC in the blood or urine does not constitute impairment as with alcohol and some other drugs. In fact, the more regularly a person uses marijuana (such as for medical patients), the less impairment they experience. Therefore, a person who is a medical patient might have a high level of THC in their blood, but show little to no impairment on the road when compared to someone who only consumes occasionally. The second issue relates to measurement. Prior to legalization, alcohol was tested for first at the scene of an accident. If alcohol was shown to be a factor, many times the person was not tested for anything else. After legalization, states started testing for marijuana along with alcohol in every crash situation. This gives the appearance of an increase in drivers testing positive for marijuana after a crash, when in reality it reflects a change in testing protocol." — Amanda Reiman of Drug Policy Alliance in Cannabis Culture
Comment by Global Ganja Report on Jun 5th, 2018 at 2:24 pm

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