
Marijuana Users Are Safer Drivers Than Non-Marijuana Users, New Study Shows - zoowar
http://www.sfgate.com/cgi-bin/article.cgi?f=/g/a/2012/04/06/prweb9375729.DTL
======
keypusher
This source is extremely questionable. This is basically a blog post
([http://www.4autoinsurancequote.org/uncategorized/reasons-
why...](http://www.4autoinsurancequote.org/uncategorized/reasons-why-
marijuana-users-are-safe-drivers/)) and a press release
(<http://www.prweb.com/releases/prweb2012/4/prweb9375729.htm>) summarizing
some reasons that marijuana users are less dangerous on the road than drunks.
There is one study linked by the NHTSA which showed they drive slower than
drunks, and the rest appears to be pure conjecture. All of this is this re-
interpreted in the SFGate article to suggest marijuana users are safer than
non-marijuana users. While I agree with the sentiment, this article is of
questionable validity and does not really fall into the tech or programming
news that belongs here.

~~~
billpatrianakos
I agree with you in general. One point on this belonging here though: HN isn't
_only_ about tech and programming. The submission guidelines say that anything
hackers would find interesting is okay. So this one is just a judgement call,
it's not totally cut and dry. I can see how it can be debatable. That said, I
think a lot of us are marijuana smokers (at least that's the vibe I get from
others I've met here) and many of us are all about progressive ideas like
legalizing marijuana and such. I'm don't exactly fall into that category this
time but I can still see why it's of interest to many here.

------
benologist
This is the press release equivalent of infographic spam - obscure site
manufactures some substance-less eye candy, or in this case pander candy, to
generate backlinks.

~~~
billpatrianakos
Yes! It's so easy to get suckered into a discussion about the validity of the
study or on marijuana use in general but what you said was my first reaction
to the post. For such a bunch of smart people I wonder why we get suckered in
like this.

------
tokenadult
The underlying study

[http://www.4autoinsurancequote.org/uncategorized/reasons-
why...](http://www.4autoinsurancequote.org/uncategorized/reasons-why-
marijuana-users-are-safe-drivers/)

does not say what the headline here (which is, correctly, the original article
headine) says. The claim in the lead paragraphs of the study is actually much
more nuanced: "There have been several studies done over the past 20 years and
every one of them has revealed that using marijuana actually has a very minor,
if any, effect on the ability of a person to drive a car or other vehicle."

Anyway, that conclusion still suggests taking a close look at the study
methodologies

<http://norvig.com/experiment-design.html>

to see if the studies were really well designed to describe general reality or
not. Much more study needs to be done before concluding that, for example,
increased marijuana use would invariably lead to increased road safety, which
someone might mistakenly conclude from the headline statement of the article
kindly submitted here.

~~~
Alex3917
The link you are pointing to is a blog post, not a study.

Also, if you read the underlying studies you'll see that the ones where they
give drivers marijuana under controlled conditions usually don't result in any
increased risk at all, whereas with alcohol it's very easy to see a huge
increase in risk using the exact same methodology). The second kind of studies
they generally use are observational studies, which tend to peg the underlying
risk increase from marijuana at around 2x (as compared with alcohol, which
gives on average a 3x increase at the legal limit). However, the authors of
these observational studies themselves say that this is most likely actually
an overestimate of the risk, not an underestimate. Here are the caveats from
one recent metastudy:

"Although this meta-analysis provides compelling evidence for an association
between marijuana use and crash risk, it is impossible to infer causality from
these epidemiologic data alone. A more rigorous assessment of the nature of
the relation between marijuana use and crash risk is complicated by several
factors. Among them are bias from measured and unmeasured confounding and the
difficulty posed by polydrug use. Although most of the studies included in
this meta-analysis considered some confounding variables in evaluating the
association between marijuana use and crash risk, adjustment was usually
limited to a few measured covariates, such as age, sex, and alcohol use.
Additional variables that may confound the relation between marijuana use and
crash risk, such as exposure to driving and risk-taking propensity, are often
difficult to mea- sure and thus are not readily available. Other factors
confounding the relation between marijuana use and crash risk are divergent
definitions and assessments of marijuana use across studies.

Different methods of assessing marijuana use (e.g., self- report, urine tests,
and blood tests) may have different levels of validity and reliability (39).
Most of these screenings determine whether marijuana was used within the past
few weeks, whereas acute impairment in driving skills from marijuana use lasts
only 3–4 hours (39). _Furthermore, because marijuana is an illicit drug in
most countries, it is possible that drivers in the comparison groups might be
less likely than those involved in crashes to submit to testing, which could
lead to overestimation of the effect of marijuana use on crash risk (43)._

Polydrug use represents another challenge to determining the role of marijuana
in motor vehicle crashes. Polydrug use by drivers is common, with up to a
quarter of drivers injured in crashes testing positive for 2 or more drugs
(including alcohol) (42, 73, 74). Although it is necessary to understand the
effect of individual drugs on driving performance, the high prevalence of
polydrug use by drivers makes it difficult to do so. On the other hand,
assessing interaction effects on driving safety of different drug combinations
based on epidemiologic data would require very large study samples,
comprehensive drug testing data, and tremendous financial and other resources
(42–44, 75, 76). One of the studies included in the meta-analysis evaluated
the effect of marijuana in combination with alcohol on crash risk and found
that the combination of marijuana and alcohol confers an exceptionally
heightened risk to driving safety (68). Experimental studies show that
cannabis and alcohol affect different cognitive functions that may interact
with driving performance (41). Specifically, cannabis seems to impair
automatic behaviors, such as tracking, at low doses and impair ability to
perform more complex tasks at higher doses, whereas alcohol seems to more
readily affect functions requiring cognitive control (41). While both
marijuana and alcohol can impair driving performance, there appears to be
greater variations in effects of marijuana compared with alcohol (41)."

source: Marijuana Use and Motor Vehicle Crashes

Mu-Chen Li, Joanne E. Brady, Charles J. DiMaggio, Arielle R. Lusardi, Keane Y.
Tzong, and Guohua Li _

------
Alex3917
I don't see any evidence that they actually did a study. The link to the study
just takes you to a top ten list.

------
aaronbrethorst
I've read conflicting reports before. Seattle's alternative weekly, The
Stranger, has been talking a lot about pot and driving in light of the ballot
referendum we'll have this year on pot legalization in Washington state. Here
are a couple choice bits:

    
    
        The report finds that only one of the participants had active THC levels above 5 ng/mL on "admission (day 1)," which suggests that the woman was high when she arrived...The woman had reported smoking four blunts per day.
    

and,

    
    
        Likewise, Grotenhermen et al found in 2005: "The crash risk apparently begins to exceed that of sober drivers as THC concentrations in whole blood reach 5–10 ng/mL."
    

[http://slog.thestranger.com/slog/archives/2012/02/24/sorry-m...](http://slog.thestranger.com/slog/archives/2012/02/24/sorry-
medical-marijuana-activists-your-study-doesnt-prove-that-i-502-will-nab-sober-
drivers-for-duis)

So, in other words, yes smoking pot can impair your ability to operate heavy
machinery, but you have to be smoking quite a bit (or not used to it,
ostensibly).

------
th0ma5
The study has a statement that smokers have a lower responsibility rate in
accidents, but I'd be very curious about response time to unexpected events
that can occur while driving. Granted, if you're going slower, you would have
more time to respond.

~~~
Alex3917
"I'd be very curious about response time to unexpected events that can occur
while driving."

That depends on the dosage, the person's tolerance, the route of
administration, how long it's been since the person used the substance, etc.
There isn't going to be a single number.

That said, someone driving at the legal limit for alcohol has on average a 3x
risk of causing a fatal accident. Whereas someone under the influence of
marijuana generally has a risk of less than 2x, meaning that it really
shouldn't be illegal.

------
dutchbrit
As someone that occasionally smokes a joint, I really don't feel safe driving
- but joints can have different effects on different people, the strength
etc... Someone that smokes up daily is more resistant than people that smoke
on small occasions

------
crusso
Of course they're safer. They're sitting in their driveways, giggling their
heads off because of the funny shapes of their keys until they remember that
they're hungry and head back inside for those Doritos that fell behind the
couch the other day.

------
billpatrianakos
Seems like another case of using statistics to prove anything. It's not the
study I don't believe but the interpretation. Before I go on, I'll give full
disclosure: I'm on the board of a drug use prevention/treatment charity that
works closely with government agencies and private companies that research all
types of drug use and related subjects like that of this article. I'm also a
former poly drug abuser (that means I was a gigantic stoner some years back
too).

I think the implications made here are dangerous. They encourage current pot
smokers to keep driving stoned and sends the message that driving stoned is
safer than driving sober. That's just not so.

The reason for the statistic showing marijuana users being responsible for
accidents less than sober drivers may simply be a product of the fact that
there are just less stoned people driving than sober people.

There's no doubt that marijuana impairs your ability to operate a vehicle. It
slows reaction times and messes with one's perception of speed and distance.
It also has an effect on focus. Some people become distracted while others
focus too strongly on one particular thing. That effect seems dependent partly
upon dosage used and the individual.

Trying to be cautious and actually doing it successfully are very different.
Slow driving does not amount to safe driving. Driving slowly can lead to
accidents just the same as speeding. Driving requires you to be mindful of
many things at once. Going back to what I said about focus, being high while
driving can make the task overwhelming for those who experience a lack of
focus while under the influence or it can a driver to be far top focused on
one particular aspect of diving. For example, a diver can be so focused on his
speed that he doesn't notice the guy tailing him too closely in the rear view.
Driver has to stop short because he misjudged the distance and speed of the
cars in front of him and wasn't focused enough on them causing the guy tailing
him to crash. That's an avoidable situation and one where the stoned driver
would not be at fault. Regardless of whether the driver who was tailing too
closely shouldn't have done that the point is that this is an example of an
avoidable situation that is actually very realistic.

I'll concede that marijuana is far less dangerous than alcohol. In fact,
despite my position on the board of the charity I mentioned and despite my
less-than-good experience with drug use and subsequent rehab, I still take the
position that pot is generally harmless. So what I'm saying isn't coming from
some hard line "just say no/all drugs are evil" perspective but we can't just
deny that marijuana use doesn't impair you in the ways I describe. I don't
even believe its bad for you (except for inhaling the smoke - even if it a
billion times less dangerous than cigarettes it's still never a good idea to
inhale any kind of smoke). Unfortunately, articles like this will give some
people the impression that marijuana is good for you, absolutely, and only
good things can come of its use. That's irresponsible and one single study
showing this will not convince me that driving while stoned is safer than
driving sober.

As far as I'm concerned this is just a really catchy article that should not
be taken at face value. The study could have major flaws and for all we know
it may just be a way to get publicity for the insurance company that sponsored
it. The spin on this is really irresponsible. Even total stoners like the kind
my friends and I once were should take it with a grain of salt but I doubt
they will because it's just more reinforcement for their beliefs surrounding
marijuana use. You know what I mean... There are always those groups of
suburban, upper middle class white kids that are nerdy then discover weed,
smoke some, turn into stoners, and then they all talk about how marijuana is
the cure for everything from cancer to aids to the common cold and a way to
avoid death itself. It's those kids I fear for when they read this.

~~~
bunderbunder
_Driving slowly can lead to accidents just the same as speeding._

Amen. The first thing I thought of when the article mentioned driving slower
was that in my experience the most common hairy situation I see on the freeway
is the chaos and disruption that results from someone driving significantly
slower than the general speed of traffic. Or merging onto a busy 65mph highway
at 50, or similar.

------
ktizo
There was a UK study from the Transport Research Laboratory in 2000 that said
that people who were slightly stoned tended to keep their distance more and
their speed down.

People who were boxed were rubbish however. Sobriety is generally the best
state for driving.

