Bicycle helmets III

Last post about bicycle helmets, I mentioned that their defenders talked about risk reduction, but never brought out any actual risk numbers.  So let me do that now.

Before I start, let me ask you: how low would the risk have to be for you to withdraw your recommendation that I wear a helmet?  You can't insist on zero, because then you'd have to wear a helmet as a driver and pedestrian.  So you must have some minimum risk level in mind.  Maybe not a real number, but an intuitive idea.

So, let me ask you: suppose a helmet saved 100 lives, per million people, per year.  Is that low enough that you'd realize it's not worth it?  What about 50 lives? 10 lives? 1 life?  Half a life?  One-tenth of a life?

Think about it, before you read on and I look at some actual data.

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During a Google search, I found this Coroner's Report from the Province of Ontario, that looked at all bicycling deaths over a five year period, 2006 to 2010.  I'm sure there are other sources of data, and I expect the numbers to be roughly the same.  (In any case, I haven't analyzed many multiples of sources and picked the one most favorable to my argument.  And, indeed, even if the numbers were off by double, or half, I don't think it would make that much difference.)

In that five year period, there were 129 cycling deaths in Ontario.  The report breaks them down in a number of ways, including by helmet use.  It says:

"In this Review, only 34 of 129 cyclists (26%) sustaining a fatal injury were wearing a helmet. Of particular concern was that observation that, despite existing legislation, only 1 of 16 cyclists (6.25%) under the age of 18 who died were wearing a helmet.

"In 71 of the 129 cases (55%), the cyclist sustained a head injury which caused or contributed to their death. In 43 of those 71 (60%), a head injury alone (with no other significant injuries) caused the death. Those whose cause of death included a head injury were three times less likely to be wearing a helmet as those who died of other types of injuries."

As an aside, I find the presentation a bit biased ... it seems more an attempt to promote helmets than to give us the actual data.  I'd expect that in an op-ed or an internet comment, but not in a coroner's report.  (And, what's with "three times less likely"?  Taken literally, that means that some people were brought back from the dead.  I'm going to assume they mean "one-third as likely.")

Anyway, I had to solve a couple of equations to get what must be the real numbers:

-- of those who died (at least partially) of head injuries, 10 of 71 (14%) were wearing helmets.

-- of those who died of other causes, 24 of 58 (41%) were wearing helmets. 

That makes the numbers work out: 41% is around three times 14%.

So, how many lives would helmets have saved? 

Well, if helmets had nothing to do with head injuries, we'd find 41% of riders who died from head injuries had been wearing helmets.  We'd still have 10 deaths from the helmet wearers, but now we'd have only 14 non-helmet wearers (that is, we'd have 10 of 24, rather han 10 of 71).  So, the extra 47 deaths would have been averted by helmets.



(This is consistent with other reports that helmets cut deaths by 30 percent: 47 deaths out of 129 works out to 36 percent, which is close.)

Those 47 deaths were over five years, so around 10 deaths per year.

The population of Ontario is about 13 million.  So, the annual death risk from not wearing a helmet is around 1 in a million.  Not everyone is a bike rider, though, so let's maybe call it 1 in 250,000.

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To put that in perspective: for driving, the death rate in Canada is 9.2 people per 100,000, which is around 1 in 11,000.  You're around 20 times more likely in a car crash than you are to die a non-helmet-related death in a bike crash.

Therefore, the increase in safety from wearing a bicycle helmet is the equivalent of improving your driving safety by 5%. 

A more intuitive way to equate the risk is by driving distance.  There are 8.2 fatalities per billion miles driven.  To get the equivalent risk of riding helmetless for a year -- 1 in 250,000 -- you only need to drive 487 kilometers -- once.  That's 300 miles.  One five hour drive.

I drive from Ottawa to Toronto around once a month, for about 500 miles.  To those of you who are scared for my helmetless head: why aren't you scared about my monthly trip?  Why aren't you also demanding that I take a plane, or a train?


For those of you who worry about my helmetless head costing tax money in medical care ... if I eliminate one trip to Toronto, will you now be happy, since I'm actually saving you more money than if I wore a helmet all year?

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Now, you might say, a 5 percent increase in driving safety is a lot!  Well, you want to know an easy way to increase driving safety by 5%?  Don't drink.

The legal breathalyzer limit, most places, is .08%.  In Ontario, they take your license for a day if you blow over .05%. 

But, .03% is perfectly fine.  Aside from the most rabid MADD activists, nobody's going to demand you take a cab at .03%, which is just a couple of drinks.  They'll just say, "be careful".

Well, those two drinks increase your risk by more than 5 percent.  You can see why, if you criticize me for not wearing a helmet, when you happily drive home at .03%, I'm going to be irritated at your double standard.

Oh, and when I say "more than 5%", I mean, according to this study (.pdf), 190%.  In that light, I'm sure even ONE beer will increase your risk more than 5%.  If you assume a constant risk increase (like compound interest), a level of .01% raises the risk 43%.  That's not even a whole beer ... well, maybe a whole beer in Oklahoma supermarkets. 

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The Ontario report also notes that in 21 of the 129 deaths, the cyclist was encumbered by unwieldy cargo, like shopping bags hanging from the handlebars.  That's 16 percent of deaths.

My own observation is that far, far fewer than 16 percent of cyclists are doing that.  Let's suppose it's 8 percent, which is probably still too high.  That would suggest that shopping bags increase the risk by around 100%.  Actually, it's probably much more than that: if you're wobbling about with groceries, you probably aren't out for a 25 mile ride.  I bet the risk is at least triple.

Helmetlessness, on the other hand, is only around 40%.  


Oh, and, by the way ... I don't ride encumbered.  I have panniers.  So you can reduce my risk by 16 percent right there.

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Here's the breakdown by what the dead cyclist hit:

102 - Car/Streetcar
15 - Nothing
2 - Other bike
2 - Train
1 - Pedestrian
3 - Unknown

It looks like cars are the main danger, doesn't it?  Suppose you don't drive on roads much, just on bike paths (like I do).  You'd think the risk would drop by 80 percent.  That is: driving on roads is 300 percent riskier than driving off road.

I see lots of cyclists using the road, when there's a perfectly good bike path right beside them, that goes roughly the same place.  Why aren't you upset about their risk?

More important for me, you have to discount *my* risk?  Instead of 1 death in 200,000 per year, it's probably ...  well, it's probably around 1 death in a million per year.  Generally, I'm only on major roads when I'm crossing them, or using them to get from one bike path to another. 

So, even if I had been riding my bike, without a helmet, since the birth of Jesus ... I'd still only have had a 1 in 500 chance of being killed, in that time, by my bare head.

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Last post, commenter Swoods made me realize that we can quantify the risk pretty well.  Economists have studied the value of a life, in terms of how much extra money people are willing to give up, or earn, for a given probability of death.  (Like, for instance, coal miners, who have a higher risk than, say, gardeners.)

A typical number is $6,000,000.  That sounds reasonable. 

(For instance: there are around 47,000 underground coal mining jobs in the US.  Thirty deaths a year is typical.  At $6 million per death, miners would have to earn an extra $4,000 or so to compensate them for the risk.  That doesn't seem out of line.


Other such calculations come up with similar, reasonable numbers.)

Suppose my helmetless risk is 1 in 500,000.  That's $12 a year.

But, to be honest, I probably value my life at more than $6MM.  So let's double it, to $24.  Let's double it again, to take injury into account, instead of just death.  Now we're at $48.

I'm willing to accept that.  It's not an unreasonable risk I'm taking, at all, $48 worth to not wear a helmet. 


In fact, I bet if someone invented an invisible "force field" helmet, that let you get all the safety of a helmet without having to wear one -- and it was $48 a year -- many of you would buy it. 

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It occurs to me, as I write this, that this is perhaps a reasonable framework for deciding what risks are OK and which aren't.  Look at the cost to the risk-taker, and the benefit.  $48 a year for helmetlessness is cheap.  $4800 wouldn't be.  I'd probably be willing to consider helmet laws if the risk were 100 times as high. 

According to this story, not wearing a seat belt makes you 47 times as likely to die in a car crash.  That gives you a 1 in 100 chance of dying per year, assuming you drive 25,000 km.  That's huge, much higher than I would have expected.  It's $60,000 worth of risk, compared to only $1,230 for the rest of us.  

So, I can see why you might want to nag a loved one who won't use his seat belt, and even pass a law.  It's over a thousand times different.

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The numbers show that the risk of riding without a helmet is quite low.  

In terms of added risk, it's 8 times as "riskier" to have a beer before driving.  It's more than twice as "riskier" to ride a bike at all (compared to staying home).  It's probably twice as "riskier" to speed in a car by 5 mph.  It's ten times as "riskier" to let your teenager drive you to the mall, instead of you driving yourself (same .pdf as before).  And it's more than 100 times as "riskier" to not wear a seat belt, which is the activity that it's most compared to.

Even if you never do any of these things -- and, by the way, I won't believe you if you tell me you don't -- I'm sure I can find other things in your life that are riskier than riding without a helmet.  Your diet, your sex life, your hobbies, your vacations ... you take comparable risks all the time.

So, again, why are you picking on bicycle helmets?  Why are your risks OK, but not mine?

Bicycle helmets II

There's a lot of bicycle helmet activism going on these days ... it's a big issue, trying to force riders, by law or moral suasion, to wear a helmet.

I don't get it.  What's going on?  Why are my friends are so horrified when I ride bare-headed, especially when there are lots of other things that don't horrify them?  In fact, I bet they'd laugh at me if I decided to wear a helmet when driving, even though, to me, it doesn't seem that much different.

Last month, I asked for a "framework" for how you decided that helmets should be worn (for those of you who believe that).  I figured this was a good audience to ask, since we're a group that has repeatedly tried to set frameworks for other questions, like Hall of Fame credentials.  We criticize those who want Jack Morris in the Hall, because we don't see any principle by which Morris belongs but, say, Rick Reuschel doesn't.  If you consider that helmetless riding belongs in the societal "Hall of Shame," then, I asked, what's the principle by which helmetless driving doesn't? 

I didn't really get any serious answers, either here or at Tango's blog.  I did get a few responses that tried a justification, but that don't hold up.

One answer was, riders should be forced to wear helmets because, when they get injured, it imposes costs on the rest of society -- such as, for instance, the cost of medical care.  But ... almost all activities impose costs on others.  People get hurt riding even with a helmet, and people get head injuries in car accidents.  Why are those things OK for society to pay for, but not riding without a helmet? 

In fact, I bet just one baseball pitcher costs society more than ten helmetless riders.  Arm injuries are pretty much inevitable for pitchers.  How many extra medical appointments do you think the average pitcher uses up?  But we don't ban pitching.

At best, the "it imposes costs" explanation is just question begging.  At worst, it's an attempt to deflect the question by asserting a principle that we're not actually willing to follow.

Another answer I got was, "because that's what society determines is unacceptable."  Which, again, is begging the question.  No religious activist would accept that abortion should be legal because "society" has "determined" it's "acceptable".  And no gay person would accept those reasons for why he shouldn't be allowed to marry his partner.

This answer is actually indistinguishable from "because we say so."  It differs only in that it uses bigger words that make it sound like it means something meaningful and important.

A third answer I've heard is, "I had a really bad accident and a helmet saved my life."  A good friend here in Ottawa actually told me that -- he wiped out and broke his collarbone, among other injuries, and it took him a long time to recover.  The crash broke his helmet into two pieces, he said.

But ... that's not really a principle.  It's an anecdote.  I think everyone should understand that one person's experience shouldn't bind the rest of us.

Just to hammer home the point ... here's an actual news story about a child that was shot while riding in a car -- but she survived because a bible slowed the bullet down.  Her sister was spared because the bullet later lodged in a watermelon on the child's lap.

Should we legislate that we all carry watermelons on our laps from now on?

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With respect, these rationalizations are pretty weak.  It does seem to me like many respondents started with the conclusion -- *of course* you should wear a helmet! -- and then tried to build a set of principles around it, which didn't test out.

I think it also goes to show that the issue is sensitive and emotional, when a community that's so used to objectively analyzing conventional wisdom still comes up with these kinds of responses.  If someone had made these arguments about wearing a helmet when *walking*, I think the flaws would be pointed out in seconds. 

What I was expecting was something to do with risk, with costs and benefits.  And that did come up.  A few people pointed out, reasonably, that the risk of helmetlessness was higher for bicycling than for driving.  From there, I expected the discussion to start talking about the actual risks.  Maybe someone would look up some numbers, and say, "helmets would save X lives for bicycling, but only Y lives for driving, and I believe the cutoff for forcing people to wear them should be between X and Y."  And then, we could go from there, trying to figure out what the threshold should be, just like we try to figure out the threshold for Hall of Fame admission.

But that didn't happen.  I don't think *anyone* talked about how big the risk has to be, even in broad terms.  I don't think there was any serious attempt to set a principle. 

As for benefits ... I think someone mentioned that helmets in cars were a bigger inconvenience -- and therefore bore a bigger cost -- than the inconvenience of helmets for cyclists.  I'm not sure about that ... why would it be different?  It's the same helmet!  Regardless, if you acknowledge that comfort and convenience are factors, then, shouldn't you try to figure out how high the costs are for cyclists?  Clearly, riders without helmets at least appear to have different preferences than other riders.  So the costs aren't obvious.

And people are different.  If I love cucumbers and you don't, and I want to pass a law forcing everyone to eat cucumbers because they have health benefits ... it'll take you about ten milliseconds to tell me, emphatically, that you hate cucumbers and who am I, who loves them, to force my preferences on you?  But, for bicycle helmets, the issue never even came up. 

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As for the costs ... on almost any scale, the risk of helmetless cycling is small.  Here's an article that claims a helmet can save around 30 percent of cycling deaths.  (It's not clear from the article, but I believe that's comparing 0% helmets to 100% helmets.) 

Is 30 percent big?  No way.  30 percent is nothing.  I'm pretty sure that riding at night increases risk by at least 30 percent.  I'd bet you that riding in rush hour traffic increases risk by at least 30 percent.  I'd bet you that riding fast increases risk by at least 30 percent.  In fact, I'd bet riding on the roads, instead of bicycle paths, increases risk by at least double. 

Do you want to ban those, too?  If you don't, then, since the cost higher, you must believe the benefit is higher, too.  Fine.  But it's different for different people.  I don't like riding at night, and I seldom do it.  Banning night riding costs me almost nothing.  Banning helmetless riding costs me a lot. 

If you want to allow night riding but not helmetless riding, logic forces you to admit that you are weighing someone else's benefit more than mine.  You're not tallying the actual cost to me, but, rather what you think the cost to me *should* be.  I *should* be willing to ride at night, because, that's worth the risk!  But not riding without a helmet, because that's not!

In fact, it's the very definition of unfair: banning something for no reason except that we believe you shouldn't want to do it. 

Now, you could come back with this response: OK, we acknowledge that you hate wearing helmets, and the risk isn't that big.  But, Phil, you're just being obstinate.  Once you wore a helmet, you'd get used to it, and your cost would drop to zero!  Long term, the benefit way outweighs the cost.  The law is our way of forcing you to give it a try!

That's the most reasonable argument I can think of, and I was expecting to get that from my original post.  And, you know, it may be true, that once I started wearing a helmet, I'd get used to it. 

But I might not.  And even if I do, who's to say that the benefit even outweighs the temporary unpleasantness? 

More importantly, do you want to live by that principle for everything?  Are you willing to submit to it yourself?

"Candy is unhealthy, so we're going to ban it.  You may not want us to ban it, but you'll get used to it and be glad you're not eating it."  "McDonald's is icky, so we're going to ban it.  You might not like eating at nicer restaurants at first, because they cost more and they're slower, but eventually you'll get used to it and not mind the extra time and money."  "PBS political specials may be boring, but they broaden your mind and make the population better informed, so we'll fine you if you don't watch them.  Don't worry, eventually you'll actually start to enjoy them."

There are literally hundreds of things you do in your life that increase your risk of something bad happening, and many of those you'd eventually get used to not doing.  That doesn't mean it's right for me to ban them.

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And what about just riding less?  A safety factor of 30 percent means that seven trips without a helmet is just as risky as ten trips with a helmet. 

Suppose your spouse or child is the one commuting without a helmet, and that concerns you.  You want him to wear a helmet, so you don't worry.  You know he really, really hates helmets, and he'd never get used to one, but you want him to wear one anyway.

He things about it, and finally he says,

"You're right, the risk of riding without a helmet is higher, and I know you're concerned about my safety.  But I hate helmets, so I'm going to reduce the danger another way.  Instead of commuting to work by bike five days a week, I'm going to commute to work only three days a week, and take the bus the other two days.  So I'll reduce my risk, not just the 30 percent you wanted, but a whole 40 percent!  That's even though I'd rather ride all five days.  See how much I love you?"

Would you be happy?  Remember: the overall risk is LOWER than if he commuted daily with a helmet. 

I'm betting you wouldn't be much happier at all.  Can you say why?

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Here's another test.  How fast do you drive?  Faster than the speed limit? 

If you drive 10 km/h (6 mph) over the limit, then, according to an Australian study, you increase your chances of having an accident -- not by 30 percent, but by over 400 percent.  Now, that sounds too high.  Another estimate (on the same web page) suggests it's only 30 percent, which sounds too low.  

I bet the real number is somewhere in between ... but never mind.  The point is, speeding is riskier than riding without a helmet, relatively speaking.

And, yes, I know speeding is already illegal.  But it doesn't carry the same social stigma.  I have had friends berate me for not wearing a helmet.  If I berated them for driving 10 km/h over the limit, they'd think I was a creep.  They'd tell me to mind my own business, and they'd probably avoid me.  And they'd be right ... nagging someone for speeding is socially unacceptable. 

That's true even though other people have a vested interest in your highway speed, since you're putting the rest of us at risk, not just yourself.  And, even though that risk is higher than for riding a bike without a helmet. 

My friend feels like he's doing a good deed by nagging me ... but I'm a creep if I nag back. 

Clearly, it's not about the risk.  It's something specific about the helmet.  It's arbitrary.


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More in a future post.

HOF selection and bicycle helmets

Whenever someone makes an argument, it's usually based on a reference to some broad principle. 

We should not discriminate against blacks, because -- broad principle -- all men are equal in rights and dignity.  We need to provide medical care for the poor because -- broad principle -- we should not let anyone die because of lack of money.  We should not put people in jail for burning the flag because -- broad principle -- freedom of speech must not be abridged.

We need those principles because, otherwise, we don't have a real debate.  I say, "we should not put people in jail for burning the flag because I say so," and you say, "we *should* put people in jail for burning the flag, because *I* say so."  That's not a rational argument.

But, if you use a principle for justification, you have to stick to it.  Some people, who don't believe in gay marriage, will say, "gay marriage shouldn't be allowed because marriage is designed only to recognize relationships with the potential for procreation."  But those same people don't think that sterile people should be prohibited from getting married, or women over menopausal age.  And so, they look like hypocritical idiots -- stating a principle, but having no intention of abiding by it.

(And they should look like idiots to you even if you also oppose gay marriage ... a bad argument is a bad argument.  However, people seem to have a tendency to defend people who share their views -- who are "on their side" -- even if they're saying dumb things.  This is regrettable, but not within the scope of this post.)

The point is, if someone invokes a principle, they should be held to it.  Otherwise, people will invoke a principle when it suits them, and pretend it doesn't exist when it doesn't suit them.  One of the most beautiful things about the US Bill of Rights is that it just states broad principles, and then the courts make sure that government lives by them.  If we say we believe in freedom of speech, and then Congress passes a law that violates the principle, the courts say, "You can't do that.  You're contradicting yourself.  If you really want your new law, amend your principle first."

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Recently, Tom Tango and Joe Posnanski applied this argument to Baseball Hall of Fame voting.  They use the word "framework" instead of "principle," which I like, because it sounds less political and less confrontational.

To those who want Jack Morris in the Hall, they say, "well, by most reasonable frameworks, it appears that Rick Reuschel is more qualified than Jack Morris.  Do you also want Reuschel in the Hall?  If not, tell us what your framework is, that puts Morris in and keeps Reuschel out.  And, be prepared to live by that principle once you declare it."

Seems reasonable, right?  But, geez, the commenters didn't get it.  One commenter put together a framework, with lists of players.  Then, Tango pointed out that it ranked Pedro Martinez too low -- and the commenter got mad!

Another commenter said things are too complicated for a "facile" framework.  So?  Come up with a less "facile" one.  If things are too complicated for that commenter, that's fine -- but that doesn't mean he's allowed to dismiss the idea that you can just proceed arbitrarily.  Because, you *have* to have some kind of principle.  It's like saying, "you know, it's impossible to codify free speech principle perfectly -- you've got shouting "fire" in a crowded theater, how do you work that in? -- so let's just forget about free speech as a framework."

That won't do.  If it's too complicated, do the best you can, but that's not an excuse for *eliminating* principles.  Otherwise, as I said, you can't have a debate at all.

Other commentators came forth with frameworks, some of which indeed put Morris ahead of Reuschel, but didn't bother checking their framework to see if they were really willing to live with the results.  Again, that misses the point.  As Tango says, paraphrasing Bill James,

"The exercise here is to force you to be consistent and end the idea of starting with your opinion and then trying to justify it. That is, you should start with the evidence, and let that lead you to the conclusion, and not the other way around."

I find it amazing that people don't get that. 

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So, I don't think anyone has answered the question yet.  I look forward to seeing some attempts.  The requirement, for answering the question honestly, is:

(a) state your framework
(b) show all the players in the HOF by your framework
(c) show all the players *not* in the HOF by your framework

Of course, no framework is perfect.  It's perfectly OK to say, "well, there are certain exceptions that I would invoke, but I haven't figured out how the principle by which I believe that, yet."  If you have, say, five or six exceptions, then, great.  If you have fifty, there's something wrong with your framework.  So, maybe add (d)

(d) explain where you and the framework disagree, and why you haven't changed the framework to make them agree.

That's what answering the question really entails.

I don't have a framework for the HOF question, personally ... the one I agree with the most, so far, is the Bill James HOF standards test.  It doesn't try to say who SHOULD be in the Hall, but, rather, who IS in the Hall.  Still, it's a pretty good framework, which, I guess, it has to be, since the reporters who do the voting are generally aligned with the fans, and so the "should" corresponds pretty well to the "is".

But if you can do better, show us.

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The HOF situation isn't the best example of failure to think things through, for a couple of reasons.  First, any actual HOF framework is going to be complicated, with so many measures of performance out there.  Second, even the fairest-minded HOF analyzers among us probably can't perfectly articulate what we're doing.  And, third, the failure to defer to the framework is obvious to the sabermetric community, since we've been dealing with the issue and the Keltner- and Morris-advocates for a long time.

So, let me give you a real life issue.

I live in Ottawa.  We have a lot of nice recreational bike paths here, that actually go to decent places, like Parliament Hill.  I ride them without a helmet.  Some of my friends are OK with that.  Some of my friends are horrified.  Some are concerned.  Some think I'm nuts.  Some think there should be a law forcing me to wear a helmet.

Are you one of those who thinks I should wear a helmet, or even that there should be a law forcing me to?

If you are, I don't agree with you.  But, try to convince me, by telling me your framework for protective-gear-wearing. 

Just like a HOF framework should explain why Jack Morris should be in and Rick Reuschel should be out, your helmet framework should be able to explain:

1.  Why cyclists should wear helmets, but not drivers or pedestrians
2.  Why cyclists should wear helmets, but not elbow pads or knee pads or stomach pads or body armor
3.  Why recreational ball players don't necessarily need protective gear in the outfield
4.  And so on.

Don't answer those questions directly: just state a principle (or set of principles) that you're willing to live by -- such that if I point out that your principle requires you to wear a bulletproof vest while jogging, you'd say either, "yeah, my principle is wrong," or "you're right, I should go buy a bulletproof vest."

This should be a lot easier than the HOF one.  It doesn't have to be perfect.  You can change your principle if need be: it's hard to get things right the first time.  Just do the best you can.
 
Personally, I do not believe that the public's advocacy for bicycle helmets is principles-based or framework-based at all.  Here's what I think, just so you see where I'm coming from:

I think a bit part of the reason (many) people advocate bicycle helmets is the "availability bias" -- it's easy to imagine horrific bicycle accidents that bash in the rider's head.  I think another part of the reason is that it's socially acceptable to wear helmets, but you get made fun of for wearing helmets for other activities that are just as risky.  I think people underestimate the diversity of human preferences, and think that if *they* don't mind wearing a helmet, other people shouldn't mind either, unless they're stupid.  I think people advocate helmets to show they're thoughtful people and not the kind of dumb rubes that don't know enough to keep their heads protected.  I think people who advocate helmets don't mind them for themselves, and therefore don't mind imposing them on other people, because it doesn't cost them anything.  And, I think people just have a strong intuitive feeling that helmets are appropriate for cyclists and not for drivers, and they don't question that feeling.  I think people are just trying to Jack Morris me into wearing a helmet.

You don't have to agree with me on those, and I don't want to debate you on those.  I'm just telling you what I think, so you understand my issue better, and why you're going to need a framework to convince me. 

Also, here's one framework I reject, that I saw on some blog a while ago: that protection should be required when it doesn't change the nature of the activity.  I'm going from memory here, but ... the idea is, that if you put on a helmet, it doesn't change the activity of cycling too much, so it should be required.  But, putting on a bulletproof vest DOES change the activity too much, so not required.

I reject that for these reasons, among others: (a) certain cyclists DO think it changes the activity, and that's why we don't want to wear a helmet.  You'd have to say, "if Joe Blow doesn't think it changes the activity," which is obviously arbitrary.  (b) wearing a helmet when driving would seem to be on the same order of magnitude in terms of changing the activity.  So, you need to add something to exempt drivers, if you believe they should be exempted.  (c) does wearing a condom change the nature of the activity?  I think it's roughly the same principle as a helmet, so you'd have to force that on people, too.

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So: what's your framework for helmet wear?  Remember: I'm not looking for an argument to tell me why I should wear a helmet.  I'm looking for a framework to tell me -- and you, and everyone -- about activities and protective gear, in general.