There was a larger discussion in a previous thread on this topic: https://news.ycombinator.com/item?id=45494730

Since then, [0] has been published and I think it's worth at least a skim. Since it's quite recent the introduction summarizes some of the most recent research.

The things that jump out at me are:

- [0]: Habitual users with baseline concentrations above legal limits perform just as well as habitual users with baseline concentrations below the legal limit, indicating that for habitual users, the legal limit doesn't have any relation to impairement.

- [1]: A study in Canada analyzed crash reports and blood tests to look at the state of drivers responsible for accidents. While alcohol had a very clear and statistically-significant influence on the risk of a driver causing an accident, THC did not.

To steelman the idea that THC causes accidents, [0] only looks at habitual users with baseline levels of THC and [1] only looks at non-fatal injuries.

My conclusion right now is that the number of drivers in accidents with THC in their blood is going up because the number of people with THC in their blood is going up, not because drivers who use THC cause accidents.

The law's assumption that this level of THC is evidence of impairment seems to be invalid.

The law would be better off measuring impairment in some way and perhaps intensifying penalties when an impairment test fails and the user has THC concentration above some threshold.

[0]: https://academic.oup.com/clinchem/article/71/12/1225/8299832...

[1]: https://pubmed.ncbi.nlm.nih.gov/31106494/

> the number of drivers in accidents with THC in their blood is going up because the number of people with THC in their blood is going up

This.

In just the short time since legalization, recreational use in my immediate vicinity (a small Ohio village, one stop light) has decidedly, undeniably increased.

I offer only an anecdotal observation, but my evening walks around town are now accompanied by a dank potpourri of skunk scents, representing I-don't-know-how-many strains of Sativa...

Indica to me that at least 30% of the population here is puffing.

That's evidence of increased public/open-air consumption, which is to be expected with legalization

Don't need to hide it anymore, especially if the local police don't have much to do otherwise

>That's evidence of increased public/open-air consumption, which is to be expected with legalization

>Don't need to hide it anymore, especially if the local police don't have much to do otherwise

Yep. At least in New York City before legalization, using cannabis in public earned you an arrest and a night in jail despite the fact that it wasn't even a misdemeanor, just a local code violation with a $50 fine.

That was done consistently (I know several folks who were caught up in such chicanery) for decades to deter folks from using in public.

But enforcement was spotty and, as usual, melanin content played an outsized role in determining who would be "enforced."

Thank goodness that's not happening anymore.

Edit: Fixed prose ('we' --> 'were')>

I have DEFINITELY noticed an increase in public usage yeah. Which is strange because that was not legalized in Ohio. Smoking a joint in your car going down the road or at the park is as illegal as it ever was.

I’m sure overall usage numbers are up because I know a lot of people who started using it after they could buy it legally, but those people are all also infrequent users and I’m sure are not driving high. The people who would be deterred by weed being illegal are probably all in the “won’t drive stoned” category. (I’m sure many infrequent users pre-legalization, myself included, were never much worried about the legality but don’t drive high because we like being alive, and we continue to not do so now.)

My fragrant walks around town put me in proximity to neighbors kicking it on their own property, visible and aromatic but not crossing the threshold into what I would consider to be 'public usage'. They're in their garage on folding chairs with the door open, or in the yard, or on a back porch.

In addition to the distinctive smell of marijuana, there is often a recreational fire (wood smoke), and/or a BBQ (sizzling meat). It's publicly visible and apparent, but on private property.

I have never been that social, haven't accepted a pass in decades, don't imbibe myself (despite my internym), and don't recommend it to young folk, but I must be getting a microdose and a minor contact high from the gentle breeze that floats through town more often since legalization.

Second hand smoke is real, yo. The wind blows.

So now children are exposed to psychoactive drug fumes in our parks, with no way to avoid them. Ideal, such progress.

The study in the post we’re responding to has actual data to show otherwise. The data was collected both before and after legalization (and Ohio is one of the states studied) and did not find a significant increase.

Weed was already easy to get. Any high schooler would have told you it was easier to get than beer BECAUSE it was illegal, nobody had a lucrative license to use for selling it to a minor.

Same thing in DC. I thought the new development in DC where we lived had a major sewer gas problem. Turns out it was marijuana.

Genuinely asking - had you never smelled cannabis before living in DC?

To claim the odor is mistakable for sewer gas is borderline funny, unless you’re slyly trying to name a new strain.

I've never smelled cannabis before in my life and don't know what it's supposed to smell like. I live in an area of the world where it's illegal and I guess not many people are smoking it. I may also have had a quite sheltered education.

This year, I went to British Columbia, and there was this weird scent everywhere that I could not describe. My wife said it was cannabis. I'm still not used to it so I don't know if I'll be able to recognize it next time I travel to North America.

In my experience, weed smells like a skunk. Which makes it really annoying to be around people who smoke, that stuff is really unpleasant to have to smell. Honestly I don't know how people can stand to smoke it with how bad it smells.

I never smelled a skunk, but the first time I smelled this weed smell I immediately loved it and still love it to this day when I occasionally smell it on the street. Even though I don't smoke. I even bought cannabis scent incense few days ago.

I guess perception of this smell, like many others is genetic.

Different weed smells different, skunk weed has volitale sulfur compounds, others varieties lack this and may smell like fruit or rosemary.

I always describe the smell like a cross between a skunk and a Christmas tree.

Am I the only one that doesn't find skunk smell not so horrid as it's generally made out to be? It's very strong, yes, but between skunk and asa foetida, it would be hard to choose ;)

Any strong smell is unpleasant, especially when it's unavoidable, from perfume to petrol fumes, even along to food smells.

Asa foetida is way worse than skunk

I’ve never smoked it or been around anyone smoking it. It’s more of a lower class thing in the U.S.: https://news.gallup.com/poll/642851/cannabis-greatest-among-... (16% of households making under $24k smoke cannibis regularly, versus 5% of households making over $180k/year).

hell yeah for being in that 5%! but why bring classism into it? in states where it’s more normalized, it’s pretty even across those differentiators:

https://doh.wa.gov/data-and-statistical-reports/washington-t...

This 100% matches my experience in Washington. I know a lot of upper middle class who use cannabis. I think the consumption of edibles might be higher in the upper middle class vs smoked. But that’s very anecdotal.

Explaining why I never encountered it. Even today usage is quite unevenly distributed. I’m from an affluent, WASPy town in Virginia. By contrast it was common even in the 1990s in the lower class parts of Oregon where my wife grew up.

Interesting. In my experience, the self-described affluent WASP-y types are exactly the kind of people that should probably smoke a joint and chill the fuck out every once in a while, lest they end up as close-minded conservatives.

Thanks for sharing!

You’re more likely to find tattoos and marijuana smokers at a Trump rally than in the congressional district where I grew up. It was solidly red when I was growing up, but today is the orderly and industrious wing of the democratic party (Biden +18).

An inspiring tale of progress and change for the better! May more southern states unfetter themselves from regressive views.

It’s entropy, not progress.

You will be. This scent is very distinct.

I had never smelled it before. It smells identical to sewer gas to me—I know what that smells like because our house was missing several drain traps.

Fascinating. I wonder if this is a genetic thing similar to people who sense soap for cilantro, except with terpenes instead of aldehydes.

Youth these days tend to say “this weed has gas” rather than “this weed is dank”. I’m unsure if that is just due to gassy strains becoming more popular or just lingo. Garlic is another rising scent.

I mean weed really doesn't smell good. If you're not turned off by the smell, it's a learned pleasure. Similar to how nearly every child will dislike the taste of alcohol, yet after drinking for a while they'll learn to tolerate or enjoy it.

It can be a very overpowering smell. When an odor overpowers, it's harder to discern one scent from another.

> If you're not turned off by the smell, it's a learned pleasure.

For me it's was love at first smell. And I didn't smoke. Just smelled it from th adjecent room. It must be genetic.

Alcohol is always dreadful for me. Same goes for cigarettes.

there are strains that, to me, smell pleasant. maybe you’re extrapolating a bit? terpenes are what make up most essential oils, in fact.

I’ve never smelled pot that didn’t stink. It does not smell like a sewer to me but it distinctly smells like skunk.

A few years ago, I moved from San Francisco to a rural area. Smelling weed in SF was not at all unusual. One summer night in the rural area, I smelled it coming through open windows for the first time. I wondered which house it was coming from and how it still smelled so strong after traveling a hundred feet or more. Then I spotted the actual skunk in our yard.

Mango, especially dried, smells and tastes of terpenes sometimes. I sometimes question why I like Mango ;)

most essential oils also smell bad in their pure form, you can always sense a smoker or a big essential oils person from their scent from afar

You're always going on about the Netherlands, surely that is based on some experience of being here and if so then you must have smelled weed it is impossible to miss on the streets of any city with more than 100K inhabitants and an active inner city.

The first time I smelt weed it reminded me of a skunk.

I could see how that might be mistaken as sewage.

It’s very skunky. I thought a skunk had been killed on an industrial road I drive sometimes. The smell was there for months. I finally realized there’s a cannabis processing facility there. Still stinks years later now.

As somebody who has no problem whatsoever with weed, it smells like pus from a tooth infection to me.

I have had dental abscesses in the past that made my mouth taste like I was in a room full of cannabis smoke.

this is surprising to hear - thanks for sharing! i still can’t help but wonder if there are some perceptive differences at play here versus something learned.

Also the amount of people in DC who drive while smoking weed seems very high(no pun intended). Based on the number of cars that can be smelled from another car while in traffic.

But this paper specifically rules out legalization as cause because the numbers didn’t significantly increase after legalization.

How does this rule anything out? It is totally possible actual usage of THC didn't increase after legalization. It wasn't one of the hardest things to find when it was illegal.

I think you’re misunderstanding. The paper says that the rates of dead drivers having THC in their system above the threshold did not change significantly after legalization. So legalizing isn’t the culprit, exactly for the reason you cite: people could get it just fine before.

Legalization does not signify usage.

Sure, but in this study 40% of people had very high THC concentrations. Is it even remotely plausible this is the baseline population level?

If the population of dead drivers with over the limit THC is 40%, and this dramatically exceeds the population average, that would strongly suggest the THC level IS an indicator of either:

1. Impairment from THC, or

2. Worse than average driving and risk management skills in those who use the drug

Do we know what the THC levels are in (1) drivers who didn't die, and (2) the population in general?

It could just be that 40% of the population is over the limit on THC all the time. Unless we can compare this against something else, and we can somehow normalize the comparison for other factors like age, I don't know how we can use the data.

This is a knowable thing, it just needs to be studied (I'm actually surprised it's not been TBH). Give people a standard set of coordination tests and then draw their blood to see what the THC level is.

If we were just interested in outcomes (in an accident or not), we should just be measuring that. But I guess if we can’t measure that, a litmus test is better than nothing.

2. young people are worse drivers and more likely to use

Right, so it might just mean that reckless drivers are more likely to smoke weed.

The expected number seems to be about 20+% (depending on assumptions) so this is higher than expected but not drastically so.

Critically, people are more likely to get in accidents later in the day and after drinking both of which also correlate with relatively recent cannabis consumption.

I would say that anyone who smokes anything (cigarettes, vapes, cannabis, crack) is indicating that they're at best not health conscious and are acting in a nihilistic way. It seems entirely logical that their risk-tolerance and judgement will be accordingly different to the general population whether they're high or not.

I can't make sense of it mathematically. A statistical distribution fitting these characteristics does not exist.

If non-weeders have an average seat belt wearing, and if weeders also have an average seat belt wearing, then the proportion of weeders inside of the seat belt non-wearing class is just equal to the proportion of weeders inside the whole population.

How are people not wearing seatbelt? I've never seen a car that doesn't make a constant annoying noise if you're not wearing it while driving. Do they mod the car to disable this safety system? That seems too far stretched...

Older cars don't have these systems. Also they are easy to bypass with a dummy buckle. There are counties where seatbelt usage is far less common than the US.

Then you've only ever seen fairly new, modern cars. Seatbelt warnings are a relatively new feature.

Seat belt warnings became mandatory in the USA in 1972[0]. From the mid 1970s until fairly recently, the warning tone would stop after a few seconds.

[0] https://www.nationalacademies.org/read/10832/chapter/5

I've known people who would just endure the warning noise until it stopped.

Many of them are just a light, and that's it. Or maybe the buzzer was burnt out lol.

My parents disabled a couple by pulling a fuse or cutting a wire, but a lot of their use of the vehicles was off road at walking speeds. They wore seat belts on the road.

I've had annoying seatbelt warnings on my cars aging back to at least the 90s.

Just click the belt in with no one occupying the seat and sit on top of it.

I never understood this though. It seems like more work and even more uncomfortable just to knowingly make things worse for yourself.

Don't fool yourself. In the end you have to obey the laws of physics and the punishment is extremely harsh and permanent.

I read comment as "don't resist our egregious power, our business is to keep becoming more powerful by arguments with different persuasive power".

I have to admit, the car safety argument is among the most persuasive, like do you want to get harmed? But in reality the question is not about "harming and nothing more", the question is about growing the egregious power AND caring about the tax payers simultaneously.

I never agreed to be bound to some "law of conservation of momentum"! I'm a free person!

Many of them stop beeping for a while (or beep way less often)

Sometimes you can change a setting in software with a programmer via the obd2 port. It's not "too far" it's easy.

But even simpler is just a pacifier. Trivial.

As a reminder of how little things change. I remember watching an old video from sometime when seatbelt laws were mandated in Texas.

People were rambling on about how they basically live in the Soviet Union.

You had me until the last sentence. Your easy assumption seems nonsensical to me.

It seems much more straightforward to me to assume impairment. This is the obvious corollary, not seat belts.

It could be seat belts, of course, but I don't think that's the obvious conclusion.

Is this a joke?

The people who don't wear seatbelts are in my observation old folks who grew up without them or before using them was mandatory. It's just their habit.

I've almost never seen a person under about age 40 not using a seatbelt.

No. I don't know a lot of people that don't wear seatbelts, but they all smoke weed. All of my friends that died in car wrecks weren't wearing seat belts and would have definitely tested positive for THC.

I don't know any old people that don't wear seatbelts.

The people I do know that don't wear seatbelts also live pretty otherwise high risk lives, drug dealers, strippers, street gang members,etc.

While I do not commonly ride in cars driven by people outside my family, my experience has been quite the opposite: when I do ride in cars with older people, they buckle up as a matter of course, while when I ride with younger people, they are much more likely not to.

The second seems eminently plausible with the correlation between driving skills and drug use both being due to higher risk tolerance.

Doesn't that support the hypothesis that high THC levels are dangerously impairing people's driving?

You need to consider other confounding factors

It is well shown that age (youth) is a major factor in accident rates.

Not necessarily, they could both be a comorbidity of some other factor (bad decision making causes both, for instance) but it certainly doesn’t refute it.

That was my first thought on reading it. Dope is for dopes!

- [1]: A study in Canada analyzed crash reports and blood tests to look at the state of drivers responsible for accidents. While alcohol had a very clear and statistically-significant influence on the risk of a driver causing an accident, THC did not.

I don't understand how this study can make that claim just looking at crash report data. The assumption that not at fault drivers are representative of people who aren't in accidents at all is pretty generous? It seems likely that folks who are unimpaired are also better at avoiding accidents / driving defensively

My preferred way to wade through a political research topic like this is to look at the aviation industry. If a pilot can not use a medical substance, then it is very likely that there is some thing there. Pilots are generally fairly high investment, and they are also fairly international in research and standards. All nations with an airforce tend also be interested in such research, regardless of current political flavor.

From glancing at it, it seems that TCH impair pilots ability. Here is such study (done with flight sims). https://pubmed.ncbi.nlm.nih.gov/1849400/

"The results support our preliminary study and suggest that very complex human/machine performance can be impaired as long as 24h after smoking a moderate social dose of marijuana, and that the user may be unaware of the drug's influence. "

I think that aviation has a lot of factors that bias its decisions conservatively. The “cost” of being conservative can be pretty easily borne in aviation. As an example, Zyrtec is grounding for 48 hours after taking. I think most Zyrtec users drive daily and likely quite safely, but aviation can afford to ground pilots at a lower level of risk than probably makes sense for drivers.

(I have very little doubt that THC is impairing; that pilots can’t legally use it is only very loosely related to that likely linkage.)

I think you miss the point of the comment you replied to.

> The law's assumption that this level of THC is evidence of impairment seems to be invalid.

I think most will recognize that THC causes impairment. The question that (AFAIK) is unanswered is if it can be measured simply by looking at the concentration of THC in the blood.

In fact, if you look into the mechanisms for alcohol tolerance vs THC tolerance. What you'll find is that alcohol tolerance is a result of the body developing fast paths for breaking down ethanol. Meaning the same BAC will have the same intoxication level, the body just works harder to keep the BAC down.

THC tolerance, on the other hand, appears to be the THC receptors becoming desensitized to THC. Which means the body doesn't appear to metabolize THC faster as tolerance builds.

That's where a blood test might not be a good indicator of THC impairment.

What the aviation study show is that the impair can continue for a very long time after a single small use. A blood test might be a terrible indicator how how much the impairment is, but the question then is how much tolerance you need in order to have zero impairment under some levels of THC. It also but a bit of doubt that even after 24hrs the impairment can be noticed, long past where the user subjectively feel any effect.

Alcohol tolerance might even be a positive here, since a drinker can drink a glass of beer 24hrs before a flight and be fairly certain that the ethanol has been broken down, regardless of tolerance. If THC metabolize slower as the body builds tolerance, then the impairment may continue for a longer time at a lower intensity even for a small dose, increasing the period of uncertainty.

The question then becomes "what level of impairment is tolerable".

Driving doesn't require perfect cognition, just good enough. If we went for perfect then anyone over 65 would be banned from operating a car.

And I think that's the hard thing with THC. Yes you may be impaired 24 hours later, but how impaired and how does that compare to age related impairment.

I could see that. In Sweden there were recently a buss accident where a health issue with the driver caused them to black out, killing several people and injuring even more. We put a lot of trust in commercial drivers that are responsible for managing people and several tons of moving vehicle. Pilots employed by commercial airlines generally have an age limit at around 65-68.

What level of impairment is tolerable when the buss driver are driving on the highway at highway speeds?

Thanks! Macroexpanded:

Nearly half of drivers killed in (Ohio County) crashes had THC in their blood - https://news.ycombinator.com/item?id=45494730 - Oct 2025 (125 comments)

If that's the conclusion you'd also expect 40% of the population using it.

I would expect there to be significant overlap between the demographics of those who more commonly get in accidents and those who use THC. Based on nsc.org, it seems like the majority of car accidents are with drivers 25-34 years old, and occur more frequently late at night on weekends. That generally matches the profile of the stereotypical THC user. It is hard to find good numbers of THC use.

Remember that not all the population drives, nor are accidents randomly distributed in the population.

https://injuryfacts.nsc.org/motor-vehicle/overview/age-of-dr... https://injuryfacts.nsc.org/motor-vehicle/overview/crashes-b...

So in other words, people with a less risk-averse personality are more likely to engage in risky behaviors

”That generally matches the profile of the stereotypical THC user”

Got a source for that claim?

That sounds about right to be honest

But the truth is that habitual users are always impaired. Source: former habitual user.

I’ve never been a smoker, but I’ve known a lot of friends who went through periods of smoking multiple times per week or even daily for periods of time.

Every single one of them denied impairment during those periods. Often vehemently so, belittling anyone who suggested they might be impaired as having succumbed to propaganda.

Every single one of them remarked that they were sharper, more alert, and had better memory after stopping.

It’s an interesting phenomenon to watch. I think it’s becoming more socially acceptable to acknowledge that marijuana causes impairment even after the obvious effects have subsided, which was a taboo topic in the years when saying anything negative about marijuana would get you attacked as being pro-prohibition or pro-imprisonment of drug users. I even remember one of the big technical forums in the 2010s had a long debate thread where people were claiming that THC made them better drivers and citing YouTube videos and “studies” to back it up. It would be rare to see anyone try to make that claim in today’s environment.

> Every single one of them denied impairment during those periods. Often vehemently so, belittling anyone who suggested they might be impaired as having succumbed to propaganda.

isn't that just common addiction response?

"no, nothing's wrong with me. my drugs aren't the problem - you are the problem"

I think most addicts when not high/drunk/fucked up off their substance of choice would admit that they they are more impaired and not good to drive when they are on their substance of choice.

But you'll still find some small percentage of them claiming they wouldn't be impaired.

Source: have actually spend a lot of time around addicts.

Isn’t it suspicious that no matter what the circumstances, their current decision-making is correct and their past one wasn’t? It seems somewhat self-unaware.

You have to tune down your self-estimate’s value if your self-estimate shows historical poor performance.

Anecdata: There are neurochemical upregulation effects to daily THC use over time, and upon discontinuance that upregulation (which can take months or even years to wear off and perhaps not) is in itself quite apparent.

Got any real sources? I've been a daily user for over 10 years and also have a spotless driving record.

> I've been a daily user for over 10 years and also have a spotless driving record.

I knew a guy who drove home from bars unquestionably over the legal limit (example: 4-5 drinks in 90 minutes) every single weekend for years without getting caught or getting in accident.

It doesn’t mean he wasn’t impaired.

That's not quite the same though. The claim is that because I'm a habitual user, I'm always impaired. Which amounts to over 100k miles of impaired driving over the last decade.

You're only expected to crash 500 or so times per 100 million miles as the base rate[0]. If you were impaired enough to have 2x or 3x the risk of crashing then it's entirely possible that you wouldn't crash, or that other factors would play a larger role.

[0] https://www.friedmansimon.com/faqs/how-common-are-car-accide...

You probably are compared to your baseline self (another comment goes more extensively on this subject) but maybe you have enough driving skills and common sense to minimize the risks somewhat.

Planning, good sense, and caution go a long way to compensate for physical impairment. Weed is different from booze in that booze increases risk taking, which makes driving such a danger. But that doesn’t mean weed doesn’t impair in some material way compared to baseline.

Your average driver on alcohol: goes 100 miles per hour into a tree

Your average driver on weed: drives 5 miles per hour to the taco bell drive thru

Being freshly high is probably 2 quick beers, I'd think I was baseline after maybe 45 minutes. A massive edible might be 5, and I'd take like 3 hours I'd guess.

Alcohol is so much more impairing. I think just being a daily user isn't the issue. It's the proximity to last use and obviously quantity.

we both know one does not get impaired by spliff or two the same way she does after drink or two.

In the south people drive drunk over the legal alcohol limit all the time, most don’t crash. Doesn’t mean you shouldn’t do it.

It depends on the level of your habitual use. A 5mg gummy every evening is probably fine.

I’ve seen plenty of people who are essentially using THC vapes like nicotine vapes, in that they use them every few hours and start to get anxious if they don’t. Stoned driving has become normalized - between seeing people lighting up behind the wheel on snap map, seeing it on TV (this happened in The Rehearsal season 1), and seeing it in person, it would take a lot to convince me otherwise.

If you’re high all day every day, that may be your normal, but it doesn’t mean you’re competent to drive.

In my personal experience, it took a very long time to fully get through a high dose of THC - usually at least a full night sleep, but sometimes more like two, before my reaction times came back. Notably, it takes much longer for the impairment of THC to wear off than the subjectively enjoyable experience of being high, so you can “sober up” but still be impaired.

If you’ve been getting high every day for 10 years, it is hard to take seriously that you would know if you’re impaired. Kind of like vegans who haven’t tasted dairy for 10 years tend not to be reliable judges of the quality of vegan mayo - how could they possibly know?

I've been high basically for 15 years straight and was a professional athlete during that time in a sport that requires a lot of coordination. I know many other athletes that are heavy users, the majority of the best athletes I've ever known were actually. So how do you think that works?

I don't trust anyone else on the road because all of you are comically bad drivers compared to someone like me.

> Kind of like vegans who haven’t tasted dairy for 10 years tend not to be reliable judges of the quality of vegan mayo - how could they possibly know?

Wait, how is mayo, vegan or not, related to dairy?

For some reason, people lump eggs in with dairy, presumably because they're unaware of the difference between hens and cows. You'd have to have quite a lot of detectable THC in your system to confuse the two, but here we are, people think that eggs are the same as milk.

To be fair, my milkman delivers eggs as well as milk, cream, and butter, but they come from a totally different farm.

Dairy is a category that depending on context may or may not include eggs. In this case the distinction doesn’t matter. Vegans wouldn’t have experience with strictly defined dairy or eggs.

TIL! I am not American.

A perfect vegan alternative to mayonnaise is aioli, which consists only of garlic, olive oil, and salt.

If we're doing anecdotes I'm sure there are lots of drunk drivers with spotless records.

I understand that you're taking issue with the idea of always being impaired, but the article indicates that there's a pretty clear association between having ingested THC and being in a car crash.

Don't we need baseline levels to see the association?

You think 40% of the population is using? That seems like a pretty big reach to me.

I have no idea, but we should know the baseline if we want to know the effect

There’s also an association with having drank water and been in a car crash. This on its own can’t reasonably inform any opinions, more context is required.

> There’s also an association with having drank water and been in a car crash

This is blatantly intellectually dishonest. If 100% of people drink water then it’s not surprising when 100% of people in car crashes have been drinking water.

If less than 40% of the population has impairment levels of THC at any given time but 40% of deceased car crash drivers have impairment levels of THC in their blood, you can’t pretend that THC use is equivalent to drinking water.

The mental gymnastics being done in this thread to try to ignore this study are fascinating.

> If less than 40% of the population has impairment levels of THC at any given time but 40% of deceased car crash drivers have impairment levels

You're looking at two different populations in this and your other comments, drawing a false equivalence. The study is over a 6 year period, over which 103 people (40%) tested positive for THC. You're saying that because the number of people who self-reported consuming THC in the last year is 20%, that means the result of the study is eye popping and shocking because the number is 40%. But you cannot directly infer elevated risk just because a subgroup has a higher prevalence than the general population without controlling for exposure and confounders. Especially considering what we are talking about is people self-reporting they are criminals.

Moreover, fatal crashes are not randomly distributed across age groups or vehicle types, and younger people, because they are not as experienced, they drive more often, in smaller cars with fewer safety features, are more likely both to smoke THC, and die in crashes even while sober. So there's a strong sampling bias here you're not accounting for.

And this isn't downplaying the results, it's pointing out its limitations of the study and warning you not to read into it what isn't there. You seem to be shocked by the results which should cause you to dig deeper into the study. I would say the most surprising thing here is they found nothing changed before and after legalization.

> If less than 40% of the population has impairment levels of THC at any given time but 40% of deceased car crash drivers have impairment levels of THC in their blood

Yes, IF. That was my point.

Enough with the pedantry please:

"Driving under the influence of cannabis was associated with a significantly increased risk of motor vehicle collisions compared with unimpaired driving (odds ratio 1.92 (95% confidence interval 1.35 to 2.73); P=0.0003); we noted heterogeneity among the individual study effects (I2=81)".

From https://www.bmj.com/content/344/bmj.e536

> I've been a daily user for over 10 years and also have a spotless driving record.

n sample size of 1 does not prove anything.

I don't (I find cannabis unpleasant) but I don't think this is at all true.

I think serious studies would be strongly preferred here, as compared to anecdotes or conjecture. I don’t even know if I disagree with your stance, it’s just an absence of data is not convincing.

not exactly. Depends how you consume it. Smoking, yes probably. The other forms of cannabis are less obvious. They are clearer highs without smell or smoke and much less burnout.

Less coughing and effects of smoke, but the burnout is definitely due to daily THC, even if you vape it or do dabs.

(To be clear, I don't think every daily user is a burnout.)

Sure, but the problem isn’t whether or not a driver is impaired, but the degree to which they are impaired.

Well, it would be good for the rest of us on the road if people driving two tons of murder box are 0% impaired.

I'm no angel but I have gotten more diligent... I'm just reacting to "the degree". The goal has to be zero degrees of impairment when a moment of inattention can kill.

Also, my son was just hit by a driver while he was on a bike and in the bike lane. They claimed not to see him. He's fine thankfully but it's really scary to watch him ride off.

There are some occupations where we aspire to that low level of risk. But it would mean that driving can't be an everyday activity for ordinary people.

No driving if you haven't been getting proper sleep; no driving if jet lagged. No driving if your attention is impaired by grief, stress, or impatience. Or if your annual physical reveals a risk. Or if you've ever had psychological complaints.

We should absolutely make transportation safer, but it's a continuum of tradeoffs.

That's probably not the thing to tell a parent whose kid just made a dent and a black smudge on a MachE. I don't want to over index on the "think of the kids" argument, but we don't take driving seriously enough. Wikipedia says:

    Motor vehicle crashes are the leading cause of preventable death for people aged 5–22, and the second most common cause for ages 23–67.

The linked article is astounding. The attitude in this thread is astounding, too. Because driving is ubiquitous and necessary in most of the US, we've become too accepting of the problems. Yes, if you're hitting the vape pen every day you should absolutely not be driving. Jetlagged? Take an Uber. Stroke risk? Give us the keys.

Okay, that was insensitive of me.

But yes, what you say is the logical consequence (except I'm not kidding about grief and impatience).

My point really is that if we want our kids not to get horribly injured or killed, we can't just focus on "other people" making bad decisions like driving drunk. We have to acknowledge that we've collectively built a system that requires people to put each other in danger with cars, and we have to think about how to change that. Cars bring a lot of benefits like autonomy and decentralization, how do we keep that but kill fewer people?

> Cars bring a lot of benefits like autonomy and decentralization, how do we keep that but kill fewer people?

'No Way to Prevent This,' Says Only Nation Where This Regularly Happens

This is a solved problem: look at the current state-of-the-art road design documents from the Netherlands. Apply. Problem solved.

Per 1 billion vehicle-km the US has 6.9 deaths and the Netherlands has 4.7 deaths. That’s obviously better much but I wouldn’t call it “problem solved”.

https://en.wikipedia.org/wiki/List_of_countries_by_traffic-r...

(Wikipedia links to itf-oecd.org/ where those numbers come From)

My guess is better road design means less miles driven by cars (as opposed to other, safer vehicles) and therefore fewer accidents overall, even if car crash statistics remain the same.

Buy a Tesla with FSD. No, it’s not L5 autonomy, but it’s already safer than the average human driver…and autonomous cars will only get better.

The solution is to make the roads safer in general and/or reduce road use, not to take away people's keys for relatively tiny risk factors.

And in particular for the Uber situation, if taking a taxi 10 miles causes 15 miles of taxi-driving, that's less safe than driving 10 miles with a small to medium impairment.

0% impaired? We know tired drivers are impaired. Should we require drivers to demonstrate 8hrs of sleep before operating a vehicle? What about people who do ok on less sleep? I think there are obvious issues with such a proposal and those issues transfer to THC usage. I would bet, if we could measure it, a large portion of fatal accidents would involve people who are not fully rested and had missed the 8hr target multiple times in the preceding week or two

There's not really such a thing as 0% impaired. People fluctuate day to day, hour to hour, and have different baselines.

Sure.. I just was addressing the goal makes sense that drivers are not impaired. Of course nobody is perfect.

A goal like that is far enough from what is actually possible that I think it's not a good goal. Maybe a slogan.

Zero degree of impairment is only possible if we don’t have access to 2 tons of murder box. I think the way cars dominate roads and our public spaces and how they are being used is inherently dangerous.

I know this is going to get downvoted by people who cant imagine an alternative but it’s possible all the same.

I borderline want a conscription-style policy, where young adults are required to live in Boston, Philadelphia, NYC, DC, Seattle, or Chicago, car-free for a year. Americans’ inability to even imagine a world where a car isn’t the way to get around is really a problem.

Inherently means “qualities or traits that are intrinsic and fundamental, not added or external”

So yea cars are inherently dangerous.

I’m not sure who you think I’m indoctrinated by but around 3000 people are killed every year in my country by cars.

Meanwhile around 200 people are murdered each year.

I’ll give you one try to guess which one dominates the newspapers and public discourse.

And you tell me something about indoctrination, real funny

Cars are inherently dangerous, though. They're multi ton hunks of metal moving at high speeds. That's dangerous from literally any angle you can imagine.

There are ways to make it less dangerous, sure. But they're never 100% safe. Which makes them, by definition, inherently dangerous. That's... What those words mean.

Swimming pools are absolutely inherently dangerous. Why do you think lifeguards are a thing?

Like, really man? If you can't even recognize as dangerous the one activity that famously requires someone specifically trained to save people to be present, then I'm happy to end this conversation right here. It's clearly just a waste of time all around. I just hope there's no one in your life depending on you to judge what's safe and what's not.

No lifeguard on duty. Swim at your own risk.

Comparing "100% safe" vs the danger cars represent is so ridiculous I have to question if you're kidding? We're talking 40,000 people killed every year in the US alone on account of traffic accidents. And you're talking about grapes and crayons?

And swimming pools are pretty dangerous though? There are around 4,500 drowning deaths per year in the US, so on the order of 10x fewer than due to car accidents, but still quite a lot.

GP is the one who argued “not 100% safe” as evidence of inherently unsafe.

I agree with you that it’s a comically wrong threshold, which is why I offered that series that was progressively more safe but never 100% safe as examples against that line of reasoning.

Make the threshold "won't kill you 99.9% of the time, even if you have little to no training at that specific activity" then. Is that specific enough for you to engage meaningfully with the conversation at hand, and show why you think driving is at the same side of this threshold as eating grapes or using crayons?

> Also, my son was just hit by a driver while he was on a bike and in the bike lane.

Let me guess, the painted line on the road did not in fact prevent the vehicle from crossing into the bike lane? What we as a society consider acceptable cycling infrastructure is pathetic.

That works the same with alcohol - heavy alcoholic would probably need to be over the limit to feel ok and sober.

An important point is that drug users (alcohol included) lose their ability to judge their own impairment after a lot of habitual use.

They can even develop an ability to appear sober to casual observers while being impaired.

Feeling sober is not a reliable indicator of being sober. It’s referred to as delusions of sobriety.

Perhaps habitual drug users should not participate in operating heavy machinery around people?

Should alcoholics be barred from driving as well, even if they are perfectly sober when behind the wheel?

Statistically, yes they should.

Even if your point is conceded which I will state as: "the impairment levels are too so that unimpaired habitual pot users appear impaired"

40% of the general population is not a habitual cannabis user. So whether they are "high" or not, folks with high THc levels are dangerous.

Yes, you cannot drive if you smoke cannabis at all. Seems fine, now just get them off the road.

And there are alcoholics who remain highly functional well over the legal limit.

using a mean rather than median is fairly odd here. a mean is pretty much worthless without knowing distribution shape.

If you calmed down and stopped snapping at everyone, you might understand that I'm writing about how the law and a lack of studies could make some people more willing to drive high. You are substantially diminishing the quality of the discussion here.

The average (presumably arithmetic mean, though it could technically be any of a wide variety of measures) is not particulatly interesting, the median specifically would be more interesting, as a single figure.