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I think that could be a Simpsons paradox situation, right?

Wow, thanks, not to out myself as an untutored lout, but I've never heard of Simpson's Paradox. The example of Civil Rights legislation on the Wikipedia page is fascinating.

Did I see a concession on the great helmet debate?

Score one for the safety weenies!

No, not really. I've always said that you're probably better off wearing a helmet, but I can't prove it, so no change.
If it reduced head injuries by 15% that wouldn't surprise. If it reduced concussions, skull fractures or death by 15% it would. That's why I want to know what kinds of head injuries we're talking about. If it reduced head lacerations by 50% and death by 1% that's very different than reducing both by 15% - in other words, not all head injuries are the same. It would be nice to see them quantify the seriousness of head injuries before and after.

Then of course there is the change in population. Helmets work best in single person, slow speed falls - the kinds of falls that children get involved in. So if the helmet law reduced the percentage of child cyclists out there, it may be that it was that - and not the wearing of helmets - that improved safety. If our only goal were to reduce bike related injuries, we could do that by making it illegal for kids to bike.

So I still think you're probably better off wearing a helmet, but I can't prove it.

1. I'm not quite understanding the antipathy toward wearing helmets. If you're in that 15%, I'm pretty sure you'd be glad you were wearing your helmet.

2. I'm heartened to learn about the tree law. If they find out whose bicycle was stolen by those miscreants who cut down that tree in the video from a few days ago, maybe they can ticket him/her, too, and put them up for the cost of replacing the tree.

I hear you on the idea that the law might discourage kids from cycling . . . but I don't buy it. If wearing a helmet bugs people that much, they just don't follow the law. Kind of like stopping for red lights.

And it's true we don't know the type or severity of the head injuries, but it's important to note that this is a drop in the head injuries reported from hospital admissions. I think it's fair to assume they are significant injuries, such that a 15% or a 29% drop is pretty damn good.

And then there is this very recent article:

"Do bicycle helmets reduce the risk of injury to the head, face or neck? With respect to head injury, the answer is clearly yes, and the re-analysis of the meta-analysis reported by Attewell et al. (2001) in this paper has not changed this answer. As far as facial injury is concerned, evidence suggests that the protective effect is smaller, but on balance there does seem to be as light protective effect. The risk of neck injury does not seem to be reduced by bicycle helmets. There are only four estimates of effect, but they all indicate an increased risk of injury. When the risk of injury to head, face or neck is viewed as a whole, bicycle helmets do provide a small protective effect. This effect is evident only in older studies. New studies, summarised by a random-effects model of analysis, indicate no net protective effect."

http://www.cycle-helmets.com/elvik.pdf

"Do bicycle helmets reduce the risk of injury to the head, face or neck? With respect to head injury, the answer is clearly yes, and the re-analysis of the meta-analysis reported by Attewell et al. (2001) in this paper has not changed this answer."

Put the "meta-analysis" tag on this puppy.

Shawn, I wouldn't call it antipathy towards wearing helmets. I don't like mandatory helmet laws, and think they're bad for cycling. And I don't like the overselling of helmets as "the most important thing you can do" or as so important than anyone who doesn't wear one is stupid or reckless. I REALLY don't like it when government officials and doctors quote the 1989 study without knowing what it means or where it comes from or that the authors repeated the study with more controls and came up with a different answer. Doctors are supposed to be scientists, and it makes them look lazy. I have great antipathy for lazy science.

Crickey7, the article makes it pretty clear that "a drop in the number of children riding bikes after the laws were introduced... complicated the modelling on the impact of the laws." And while I agree that not all head injuries rise to the level of hospital admission-worthy, I suspect taht with kids that becomes less true. Parents are more reactive to kids injuries than they are their own.

Totally agree. My stuffed animal good luck charm is the most important thing protecting me. Mandatory talisman laws!

Forget the helmet issue, which, apparently, will always be with us. I'd like to know just how locking a bike to a tree can "stunt a tree's growth" (and WC, always bad for the tree?)? I mean, sure, if you leave it there a few weeks or more. But if it's there only while you throw down a few beers or quaff some coffee (assuming you didn't batter the tree or wedge its bole into your too-small u-lock in the process), I don't see how that could be the case.

And yes, I lock up to (appropriately sized) trees often when there is no decent alternative, taking great care not to harm the bark and not to plant my tires on top of or otherwise disturb any flowers/plants in the tree bed. Common sense and a little carefulness are all you need.

How much would head injuries be reduced if all occupants of automobiles were required to wear a helmet?

I am guilty on both counts. Occasionally riding without a helmet and occasionally locking my bike to a tree.

I'm going to defer to the arborists at DDOT’s Urban Forestry Administration on this one. But maybe "always" was overstating it. I'd say you don't really know if you're nor harming it, so it's best not to tempt fate.

Leave a comment on DDOT's blog about it.

I can get behind any effort to correct for lazy science.

The category of "head injuries" is so broad, and the sample size small, that the data must be treated with caution.

Crickey7: Why did you change your spelling, unless you are someone different.

Shazam!

Am I different? How would I know if I were not me?

You've sent me into an existential crisis. Only washcycle can confirm whether I am me or not-me.

I crashed a few years back and scraped up the side of my face. I was wearing a helmet, but didn't need to go to the hospital for it - just went home and my girlfriend and I cleaned my face up. I think there are a lot of crashes similar to this that might be counted as head injuries that are not included.

Stupid pedestrians on cell phones...

All this effectiveness of helmet talk reminds me of another recent blog post I read.

http://davesbikeblog.squarespace.com/blog/2011/6/21/pro-cycling-and-helmets.html

It questions the effectiveness of helmets in pro cycling, looking at deaths in pro cycling over the last few decades. Granted, the sample size is small, but it's still food for thought.

I've actually asked for that kind of study before, but the problem with it is we don't know the deaths per mile. Knowing how many competitive bike races, and how many competitors is the critical piece of info missing.

There was once Krickey7 and now there is Crickey7.

My alter-ego, who runs red lights, does not wear a helmet and fails to signal when passing on the trail.

Doctors are not always great with research science. For example, many doctors believe that no one should be running because it "inevitably" destroys the knees. And yet, the research shows that long-time runners tend to have fewer knee problems than sedentary people.

Some doctors will treat or hear about a specific case where someone injured their knee while running. Then they make the false assumption that running must be bad because one person injured his/her knee.

Likewise, I've run into a person or two who believes that every cyclist will automatically develop impotence simply because those people see those cases as part of a medical practice. They ignore the fact that impotence is hardly a raging epidemic among amateur cyclists. They see a few of the most extreme cases. (Could be someone who does heavy miles on a poorly-fitting bike, and continues to ignore obvious warning signs that something is amiss.) Then they conclude that since this small group of people were injured from cycling, then ALL cyclists must be facing a high risk of similar injury, when that isn't the case.

Doctors treat individuals. They aren't always so great about understanding injury risks in general. Plus, they are trained to be risk-averse when it comes to their patients.

Personally I think helmets can help in many cases, but I think a mandatory helmet law would limit the popularity of CaBi. We've seen the statistics that the accident rate among CaBi users has been very low. The rate of serious accidents even lower still.

CaBi is getting some previously sedentary people out there doing something active. That will have some effect on the incidence of obesity, high blood pressure, heart disease et al. in the future, especially as CaBi continues to grow in popularity.

Those health benefits can be compared against any possible benefits of mandatory helmet laws in this area. I don't think we'll have any mandatory laws for adults in the D.C. area anyway.

Shawn, I wouldn't call it antipathy towards wearing helmets. I don't like mandatory helmet laws, and think they're bad for cycling. And I don't like the overselling of helmets as "the most important thing you can do" or as so important than anyone who doesn't wear one is stupid or reckless.

This pretty much sums up my position. I think an argument can be made for wearing helmets as a general precaution. Just like wearing gloves. Or glasses.

But something is out of whack when, inevitably, when hearing someone go on a rant about entitled, arrogant scofflaw cyclists, the first (ok, perhaps second) thing out of the critics mouth is "OH, AND HE WASN'T WEARING A HELMET!!!"

The sort of mania that's gripped the general public regarding cycling and helmet use certainly affects cycling adoption. @Crickey7 says if you don't want to wear a helmet, you won't. But this discounts the public preassure aspect: a lot of cyclists who are helmet agnostics--when faced with the prospect of getting on a CaBi sans helmet and risk running the gauntlet of semi-rational helmet busybodies--may decide to Hell with it, I'll just drive or grab a cab.

And we know that fewer folks no bikes actually *does* have a negative health impact far greater than non-helmet use. More folks on bikes is great for public health *and* performs a traffic-calming role.

Oh, and Michael H is spot on: in matters of precautionary measures, doctors have the same prejudices as the Secret Service. More is always better.

Your average doctor will recommend that you avoid going out of the house to get your exercise--did you know it's very dangerous out there in the real world? An apple could fall on your head! Much better to do leg-lifts in a chair in your living room.

I like to think that Crickey7 is the "real" Crickey7, and Krickey7 is the cheap imitation.

A bit like "crab" versus "Krab"...

I would like to note that I though the item that would drive the most discussion on this post was the H.S. Mountain biking. I could not have been more wrong [Aside: Actually I could have been more wrong, like if I said the month after April was Hasselhoff, but you get my drift].

The Hoff!

He deserves at least a summer afternoon, though not a whole month. The afternoon of the day after the summer solstice would be appropriate.

OMG! I'm krickey7 now. Back to therapy.

But something is out of whack when, inevitably, when hearing someone go on a rant about entitled, arrogant scofflaw cyclists, the first (ok, perhaps second) thing out of the critics mouth is "OH, AND HE WASN'T WEARING A HELMET!!!"

I know I started wearing a helmet after an incident where I was biking through a downtown construction zone and a motorist tried to run me into a Jersey barrier. At the next light I went up to her window to ask her WTF she was doing, and the first thing out of her mouth was "you're not wearing a helmet."

Ever since then I've worn a helmet.

"I'd say you don't really know if you're nor harming it, so it's best not to tempt fate."

WC, that doesn't sound like you. So, we don't know, so just obey and end of discussion?

I asked this same question yesterday on the goDCgo blog and Ms. Howard has yet to post it, let alone respond.

When someone makes what appears, on the surface, to be a patently absurd statement like this and suggests that a group of people dismiss with critcal thinking (or even common sense) and modify their behavior based on it, it sort of hits me the wrong way.

BED, If you park a million bikes against a million small trees, I'm positive some of those trees would suffer damage. But I probably wouldn't know which ones until some time later - and others might suffer so little damage as to be undetectable, but would still be real.

So if I see someone parking a bike against a tree I don't know if they're harming it. But averaged out among all tree parkers, the harm they're causing is greater than zero. Can I say, "I can see that you're harming that tree?" Maybe not, because it might not be evident until days later or maybe it is only very small.

So each event has the possibility of causing harm without any possibility of making things better - so why play that game. It's like buying a $1 lottery where either you get your dollar back or you don't. It's a loser.

That's what I meant. You don't know the outcome at the time of parking, so why risk it.

WC, apply the "we don't know so don't risk it" logic to other aspects of daily life and see how well it holds up.

In fact, it's kind of humorous to note that on the DDOT site, there is a picture of a child sitting in tree, meditating. So, climbing a tree: good. Leaning a bicycle against a tree: bad.

I say, both: good.

I know the outcome when i lean my bike against a tree. The two get along quite well. Why risk it? Because no one has given me a reason not to risk something they can't seem to even explain.

Now we have posters and a campaign alerting the nonbiking public to the possibility that cyclists are killing trees...not exactly positive PR work.

Hopefully, the Urban Forestry Administration can clear up this mystery. If not, maybe they should start a new campaign about the very real negative consequences of placing an idling internal combustion engine near an urban tree.

I know the outcome when i lean my bike against a tree.

With all due respect, you don't. Not unless you're an arborist and go back to do detailed analysis. Doesn't the fact that DC's trained arborist say it's bad mean something (at least something)? Doesn't it make sense that a tree can nick the bark, or that long term contact with the trunk can rub the bark in a way that lets disease in? (And we know it encourages thieves to try and cut down trees to steal bikes, something you have no control over).

And it's not just DC's arborists. NYC parks say it harms trees. Doing a quick search I find a lot of tree specialists and government agencies that say it harms trees, but I can't find anyone (not just anyone credible, but anyone) who says it doesn't.

So here's where we stand.

1. A lot of experts say it harms trees.
2. You say it doesn't.

You're going to need more horsepower here.

"Doesn't the fact that DC's trained arborist say it's bad mean something (at least something)?"

No, in the absence of evidence, it doesn't. I would have to know whether the arborist has an agenda. Perhaps, for example, the city government thinks bikes locked to trees are visually unappealing. It may be easier to use greeness to change behavior than to talk about abstract or subjective esthetics. I suggest that the aborist do the detailed analysis (if it hasn't been done) and submit the results to the public before we go wild about bikes killing trees.

"Doesn't it make sense that a tree can nick the bark, or that long term contact with the trunk can rub the bark in a way that lets disease in?

First, define "long-term". We aren't talking about bikes locked to trees and abandoned. That isn't a bike/tree issue per se, it's an abandoned bike issue. Thus, the campaign should be about locking your bike to a tree and abandoning it. Yes, a bike *can* nick a tree and maybe damage it. If that's true and if it's rampant, I have no objection to suggesting trees not be used for lock-up. Fine. So, where is the data? "Stunt", "kill", those are strong words to use to refer to a process that, assuming it actually happens, takes decades to unfold. Keep in mind that most urban trees are removed (read: killed) long before they reach late maturity because, among other reasons, they outgrow the areas in which they are planted.

"(And we know it encourages thieves to try and cut down trees to steal bikes, something you have no control over)."

I don't know this either. I know of one such recent incident. Is this common practice? I'd appreciate some data on a "we know" statement.

"1. A lot of experts say it harms trees."

A lot? Really? Hmm...can't find anything about it with a Google search; just the same parroted mini-meme from one web site to another.

And yes, this is with all due respect. That goes without saying.

To refuse to follow the advice of a professional until you know their agenda is an invitation to paralysis.

As to the abandonment thing, I'm sure most abandoned bikes didn't start out that way. It's impossible to enforce a law prohibiting only bikes that are being abandoned from being locked to trees. Plus, the tree can be damaged if a bike is stolen or stripped while locked to it, or if the City has to break the lock to remove it. Better to avoid the abandonment issue prospectively than retrospectively, when the tree is far more likely to be damaged.

While not an arborist (albeit posessing a "pro-tree" agenda), I believe that any damage to a tree's bark, even if not readily apparent, can have a significant negative effect on a tree's overall health.

goDCgo: (strikethrough)a community of bike evangelists(/strikethrough) ‘an extremely enthusiastic band of bike-supporters’ have all contributed.

I'm surprised noone commented on this. Seems like a bit of a snarky way to talk about cycling advocates.

(wash,does the strikethrough tag not work here,or is my html that bad?)

in the absence of evidence, it doesn't.

Expert opinion is evidence. Do you make your dentist prove to you that you have a cavity and that removing it will improve your health?

Here are a couple of studies that imply that bike parking is part of the problem, and they note that tree guards improve survivability, though not just because of bike parking.

http://digitalcommons.lmu.edu/cgi/viewcontent.cgi?article=1069&context=cate

http://www.nycgovparks.org/sub_your_park/trees_greenstreets/images/how_to_assess_your_citys_st_survival_10-6-2010.pdf

First, define "long-term"

An hour or more.

"Stunt", "kill", those are strong words to use to refer to a process that, assuming it actually happens, takes decades to unfold.

It doesn't matter how long it takes. Carried out over thousands of street trees it means that every year trees die, in part, from damage by parked bikes.

Is [cutting down a tree to steal a bike] common practice?

http://www.paloaltoonline.com/news/show_story.php?id=17664

http://bostonfixed.us/forum/comments.php?DiscussionID=641&page=3

A lot? Really?

Yes. NYC Parks, DC UFA, etc... Perhaps you think they're all parroting one another, but I don't think they can ALL be doing so.

I think you have to use the "<" symbol not "("

Is it too much to just park your bike somewhere other than a tree and heed the arborists' advice, rather than go on and on about the philosophical implications for all aspects of life about embarking on the slippery slope of listening to any such or analogous guidance?

Yeah, my advice is to find somewhere else to park and every time a tree is your best option. Ask DDOT to install a bike rack there. Maybe Casey Trees will kick in some money for a few.

WC, expert opinion doesn't equal empirical evidence. It can be based on it, though I don't see that here. Opinion is, by definition, belief.

The links you gave about damage caused by locking a bike to a tree don't cut it. In the first one, we have only this, about bike racks and the "flow" of bicycle traffic, unless I missed something:

"This study suggests that physical urban design factors influence the success of young street trees; this category includes information at three different levels: tree/tree pit, building, and streetscape (listed in Table 3). The factors measured at the level of the tree and tree pit itself are more directly connected with the tree success or failure, while others, such as the presence of a bike rack nearby and the width of the sidewalk, are more exploratory in nature and may only provide insights into potential influences. All factors comprise the physical urban context into which the tree has been planted. They are the result of urban design, zoning practices, or unplanned piecemeal development and they affect the flow of pedestrians, bicycles, and motor vehicles through the environment surrounding the tree. At the same time, these factors also affect airflow, sunlight, and wind speed that can impact the growing conditions of trees (McGrath et al. 2007)."

In the second, the conclusions are prefaced with "may indicate" and don't get into whether the bike was there for x number of years or "an hour or more."

As for whether cutting down a tree to steal a bike happens "a lot" as you contend, two confirmed incidents and an anecdote expressed on an online forum hardly equates to "a lot" for me.

That's it for me. I don't see an issue with carefully locking up to an appropriately sized tree in the absence of a more suitable spot and, as far as I know, neither does the law. Your suggestion about contacting DDOT to install a rack is fine, but I don't think they'll come out that minute to do it.

Ok, you keep moving the goal posts on me - first you complained that there was only one incident of a bike being stolen by cutting down a tree. Now it is only three. So why don't you tell me how many incidents you need to accept that it does happen regularly and then I'll just run along and find that many for you and print it up into a nice report and deliver it to your house with some fresh made muffins. I can't believe you're arguing with me about this. In 5 minutes I found three cases. You're really arguing on the edges here.

"It happens but not a lot" is hardly a winning argument. So fine. It happens, but only very rarely. Still, that is reason enough to not park against a tree, since the cost of parking farther away is a few steps and the cost of parking there is the very small risk that the tree will be cut down.

Does that taste like victory to you?

As for expert opinion, I've got some. And you don't. And it also seems to meet what I would expect. Leaning things against trees does seem like, on average, it would cause harm. So you're making a counter-intuitive argument with nothing but your own layman opinion.

In my book, Expert opinion > counter-intuitive layman opinion. You're free to disagree.

@Contrarian:

I know I started wearing a helmet after an incident where I was biking through a downtown construction zone and a motorist tried to run me into a Jersey barrier. At the next light I went up to her window to ask her WTF she was doing, and the first thing out of her mouth was "you're not wearing a helmet."

More compelling evidence that Entitled Driver Syndrome is not driven in any way by "scofflaw cyclists". If every person who ever got on a bike obeyed every law every time, they'd excuse their behavior with the fact that cyclists don't wear helmets. If every cyclists always wore a helmet, it would be about Lycra shorts. If we wore baggies, it'd be halitosis.

Bullies can always think of something to pick on their victims over.

You missed the moral of the story. Contrarian vowed to adopt the helmet-wearing lifestyle, and has lived a safer, hassle-free existence ever since.

Or that coercion by car is just as powerful as coercion by gun.


You missed the moral of the story. Contrarian vowed to adopt the helmet-wearing lifestyle, and has lived a safer, hassle-free existence ever since.


Sadly not true.

How' bout adopting the helmet hairstyle?

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