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February 18, 2014

Could marijuana reforms end up making our roadways much safer?

The question in the title of this post might be a bit of foolish wishful thinking on my part, but these passages from this notable new New York Times article provides the foundation for my (undue?) optimism:

[S]cience’s answers to crucial questions about driving while stoned — how dangerous it is, how to test for impairment, and how the risks compare to driving drunk — have been slow to reach the general public.  “Our goal is to put out the science and have it used for evidence-based drug policy,” said Marilyn A. Huestis, a senior investigator at the National Institute on Drug Abuse.  “But I think it’s a mishmash.”

A 2007 study found that 12 percent of the drivers randomly stopped on American highways on Friday and Saturday nights had been drinking.  (In return for taking part in the study, intoxicated drivers were told they would not be arrested, just taken home.)  Six percent of the drivers tested positive for marijuana — a number that is likely to go up with increased availability.  Some experts and officials are concerned that the campaign against drunken driving has not gotten through to marijuana smokers.

“We’ve done phone surveys, and we’re hearing that a lot of people think D.U.I. laws don’t apply to marijuana,” said Glenn Davis, highway safety manager at the Department of Transportation in Colorado, where recreational marijuana use became legal on Jan. 1. “And there’s always somebody who says, ‘I drive better while high.’ ”

Evidence suggests that is not the case. But it also suggests that we may not have as much to fear from stoned driving as from drunken driving.  Some researchers say that limited resources are better applied to continuing to reduce drunken driving.  Stoned driving, they say, is simply less dangerous.

Still, it is clear that marijuana use causes deficits that affect driving ability, Dr. Huestis said.  She noted that several researchers, working independently of one another, have come up with the same estimate: a twofold increase in the risk of an accident if there is any measurable amount of THC in the bloodstream....

The estimate is low, however, compared with the dangers of drunken driving. A recent study of federal crash data found that 20-year-old drivers with a blood-alcohol content of 0.08 percent — the legal limit for driving — had an almost 20-fold increase in the risk of a fatal accident compared with sober drivers. For older adults, up to age 34, the increase was ninefold.

The study’s lead author, Eduardo Romano, a senior research scientist at the Pacific Institute for Research and Evaluation, said that once he adjusted for demographics and the presence of alcohol, marijuana did not statistically increase the risk of a crash. “Despite our results, I still think that marijuana contributes to crash risk,” he said, “only that its contribution is not as important as it was expected.”

The difference in risk between marijuana and alcohol can probably be explained by two things, Dr. Huestis and Dr. Romano both say. First, stoned drivers drive differently from drunken ones, and they have different deficits. Drunken drivers tend to drive faster than normal and to overestimate their skills, studies have shown; the opposite is true for stoned drivers. “The joke with that is Cheech and Chong being arrested for doing 20 on the freeway,” said Mark A. R. Kleiman, a professor of public policy at the U.C.L.A. School of Public Affairs....

Another factor is location. A lot of drinking is done in bars and clubs, away from home, with patrons driving to get there and then leaving by car. By contrast, marijuana smokers tend to get high at home....

All of these facts lead experts like Dr. Romano and Dr. Kleiman to believe that public resources are better spent combating drunken driving. Stoned driving, they say, is best dealt with by discouraging people from mixing marijuana and alcohol — a combination that is even riskier than alcohol alone — and by policies that minimize marijuana’s risk on the road.

For instance, states that legalize recreational marijuana, Dr. Kleiman said, should ban establishments like pot bars that encourage people to smoke away from home. And Dr. Romano said that lowering the legal blood-alcohol concentration, or B.A.C., to 0.05 or even 0.02 percent would reduce risk far more effectively than any effort to curb stoned driving. “I’m not saying marijuana is safe,” he said. “But to me it’s clear that lowering the B.A.C. should be our top priority. That policy would save more lives.”

My supposition based on this article that marijuana reforms could end up making our roadways much safer is a result of two potential impacts of ending pot prohibition: (1) if marijuana reform leads a number of people who would generally go get drunk at a bar to instead now just get stoned at home, the net effect will be safer roads, and (2) if enduring concerns about the impact of marijuana reform leads more policy-makers to focus on highway harms, we might see a greater effort to get much tougher on the enduring public safety disaster that is drinking and driving.

I am not expecting that we will get strong evidence that marijuana reforms end up making our roadways much safer anytime soon, but I am hopeful that researchers like Dr. Romano and Dr. Kleiman continue to stress that our modern alcohol policies and practices now impact highway safety much more than any marijuana reforms are likely to do. And, as these related recent articles also highlight, the media so far is doing a pretty good job defusing the risk of misguided reefer madness when it comes to driving under the influence:

Cross-posted at Marijuana Law, Policy and Reform

February 18, 2014 at 11:03 AM | Permalink


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Would not the consumption of marijuana at home be a function of it being illegal and therefore most people are going to make at least some effort to not be publicly visible while doing so? I could well see that pattern being something that disappears if marijuana use were no longer illegal.

Posted by: Soronel Haetir | Feb 18, 2014 1:59:46 PM

Soronel --

Excellent point.

In addition, the central premise of the argument that pot will make the roads safer is that pot will be used as a substitute for, not in addition to, booze.

I haven't attended many frat parties recently (like decades), but from the few I did attend, this certainly did NOT seem to be the case.

Posted by: Bill Otis | Feb 18, 2014 2:16:50 PM

What are the laws currently in the two states that legalized marijuana?

Can you smoke in public places? Are "pot bars" allowed?

I question the substitution hypothesis. The better hope seems to be #2 -- better public policy to deal with harms on the highway. Total criminalization of marijuana net is not the best way to advance public health and morals.

Posted by: Joe | Feb 18, 2014 4:03:24 PM

Seems like we should allow, nay, REQUIRE use of marijuana as a condition of driving. All those slow, extra-cautious drivers will mean only the mellowest of fender benders.

Posted by: Wayne-O | Feb 18, 2014 6:49:03 PM

"Dumb smoker". The phrase is redundant. Tobacco is worse than pot. Outlaw both.

Posted by: Liberty1st | Feb 18, 2014 10:45:34 PM

The Supremacy has often referred to the study cited above. If you stop all cars, and test, over 10% of drivers will be legally drunk. Drunk drivers tend to drive slowly. If that many people are drunk, and high alcohol levels cause accidents, then the carnage should be much 100 times greter, with a 1 in 10 drivers causing a crash.

The lawyer remains mired in the Medieval chain of causation idea of adverse events. The modern view is that multiple factors cluster in a space and time. The prevention of even one prevents the entire accident. So modern accident analysts list all of them. They are beginning to do the same for near accidents to prevent the full accident.

So the crash invlved a high alcohol level, a beat up car, bad road conditions, an aggressive personality, personal stress and rushing.

Drops in accident rates are better explained by technology, on the front and on the back end. The front end is car technology and road design. The back end are the lessons learned in combat surgery. These lessons may save 100 times the number of fatalities in the military.

I recommend all law students spend a half day in traffic court. Nothing you heard in law school will come up, and nothing you hear in court is ever taught. The drunk driving defense bar is soft on the lawyers to whom they owe their jobs, the prosecutors and the judges. If they were at all loyal to client, they would demand a Daubert hearing on the accusation. Then seek sever punishment of the prosecutor and the judge for the forbearance of garbage science. Because the drunk driving legal machine is a huge money machine, a lawyer bunko operation, the errors of the court are intentional and should be subject to exemplary damages.

If Draconian, feminist inspired laws have any effect, it a weak one, and one among many others. The students will soon realize, they are after the assets of the productive male.

Posted by: Supremacy Claus | Feb 19, 2014 2:26:13 AM

Meanwhile, Grits for Breakfast and others talked about a new provision that denies food stamps to sex offenders. The discussion notes that in many states there was a long practice of denying food stamps to convicted felony drug offenders.


The details would be useful to parse, but both are pretty harsh business.

Posted by: Joe | Feb 19, 2014 8:55:04 AM

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