Nov. 10, 2006
An open letter to Dr. Patrick J. Crocker, Chief of Emergency Medicine at Brackenridge & Children's Hospital of Austin, in response to the Oct. 11, 2006 press release announcing Crocker's plan of conducting a bicycle helmet study to gain ammunition for his support of a mandatory bike helmet law.
Dear Dr. Crocker,
The press release announcing your study says, "The initiative was created to test the hypothesis that an all-ages, citywide bicycle helmet ordinance will substantially mitigate preventable head injuries due to bicycle accidents...."
But it is impossible for you to come to any such conclusion because there are important factors that your study cannot measure. What's more, cyclists such as Patrick Goetz, myself, and others have explained these factors quite clearly, but you are apparently ignoring them. This is extremely disappointing. For its intended conclusion, your study is worthless.
I will detail the various factors your study fails to consider below, but let me lead with the most significant one:
Bicycle helmet laws indisputably discourage bicycling. This ultimately makes cycling more dangerous for those cyclists who remain, since cycling safety is extremely highly correlated with the number of cyclists on the road. Your study does not (and can not) consider this problem, and thus it is impossible for your study to credibly support the conclusion that mandated helmet usage means a reduction in injuries.
Support for a helmet law assumes that once the law is passed, the only thing that will change is that previously unhelmeted cyclists will start wearing them. This view is dreadfully simplistic and naïve. The unintended consequences of such legislation not only negate any public health benefit, they likely increase the danger to people who continue to cycle. As you said in your August 10 letter to the City Council, "read that last line again".
These dangers include, but are not limited to:
Cycling advocates have explained most of these issues in detail at the very same council meeting where your own testimonial was read into the public record in your absence. This hearing aired on the City's public information television channel and a transcript is available on the city's website. I also know that Rob D'Amico wrote to you directly about his concerns.
If you did not pay attention to these points raised by myself and others, that is quite disturbing. Since you are not only attempting to influence public policy but are also conducting original research to support that effort, it behooves you to notice when problems with both that policy and the research behind it are pointed out very plainly. Perhaps you disagree with the concerns raised, but if so you have not bothered to even acknowledge the existence of such dissent, much less answer it thoughtfully. I'm afraid these things conspire to make your research non-credible even before it begins.
Again, helmet efficacy, even if proven, is completely different from expecting a decline in injuries by enacting a law. You are confusing a good thing with a law requiring a good thing. A law has many unintended consequences which can turn a good thing into a bad thing, even from a public health perspective.
Here's an example of how unintended consequences work in legislation. In the 16th century the crown got the idea to levy a tax based on how many of those new-fangled glass windows people had in their homes. They figured it would be an easy way to raise money, and their revenue analysis consisted of this: estimating the number of windows that were out there, and multiplying that by the amount of tax. (Much like estimating the number of injuries prevented by passing a helmet law.) But here's what actually happened when the tax was levied, as explained by a member of Canadian Parliament:
Lo and behold, if we go to small English towns today and look at some of the Tudor homes, we will see over and over again these very clear window shaped spaces, that have been plastered over, and filled in or bricked in. Why? It was because 500 years ago people understood that they could [avoid] taxes legally and so they bricked in those beautiful glass windows all across England.1
Likewise, a bicycle helmet law will result in numerous unintended consequences, yet your limited research relies on the mistaken assumption that once a law is passed, nothing will change except that previously unhelmeted cyclists will start wearing them. But, as with the window tax, people will take other, unexpected actions in response to the law. Let us go over those unintended consequences.
1. Helmet laws discourage bicycling. (indirect effects)
Every community which has passed a helmet law that was enforced has seen the number of people who bike for transportation plummet.
2. A reduction in cycling increases the risk for the cyclists who remain.
The evidence is clear, convincing, and overwhelming that communities with the highest rate of bicycling also have the lowest rate of cycling injuries.5 The assumed reason is the safety in numbers principle: The more cyclists on the road, the more drivers are used to seeing and interacting with them. A reduction in cycling participation increases the risk for the cyclists who remain on the roads.
3. Helmet-wearing may promote collisions.
Recent research from England shows that motorists give less room to when passing helmeted cyclists vs. unhelmeted ones.6 The researcher conducting this study was actually hit twice by motor vehicles while biking, each time while he was wearing a helmet. While we've always known that wearing a helmet won't prevent collisions, we now know that helmet-wearing may actually promote injury by promoting collisions.
While failure to account for unintended consequences is the major flaw in your research, it is not the only one. Here are others.
4. Case-control studies suffer from self-selection bias.
Cyclists who voluntarily wear helmets are apparently more cautious as a group than those who don't wear helmets, or wear them only when forced to do by law. The same studies that show that helmets are 85% effective in preventing head injuries also show that helmets are 72% effective in preventing leg injuries.7 Obviously bicycle helmets can't prevent broken arms and legs. A reasonable conclusion is therefore that helmeted cyclists suffered less injury because cyclists who choose to wear helmets are more careful in general, and that we can't necessarily expect the same kind of benefits by requiring people to wear helmets who are not already inclined to do so.
5. Population studies have already disproved your hypothesis.
In the 1990's, helmet use among cyclists in the U.S. skyrocketed. And so head injuries among cyclists went down, right? No, in fact, as helmet use increased, the rate of head injuries among cyclists went up. As you like to say, read that last line again.
6. Does not consider non-compliance and non-enforcement.
In your August 10, 2006 letter to the Austin city council, you say that one reason we need a helmet law is that only 5% of child bicyclists treated at your trauma center were helmeted. You say, "This is one area where a helmet law could provide a significant safety factor for our children."
7. Fails to put its findings into context.
Cyclists account for only 2% of road injuries and deaths.9 Two percent. This suggests that a much greater public health benefit exists by requiring motorists to wear crash helmets. If helmets are not uncomfortable or inconvenient for bicyclists, then they're even less uncomfortable and inconvenient for motorists, who have the benefit of air conditioning and lockable storage for the helmet. Any argument you make for cyclists wearing helmets is an even stronger argument for motorists to wear helmets, too. Yet you're not making that argument. And you haven't explained why you're singling out cyclists among all transportation users for mandated helmet wearing.
I have focused only on the public health problems caused by helmet laws, but there are other downsides to be sure, which I will mention only briefly:
If you really want to promote bicycle safety, may I suggest your support of the following measures:
But returning to the issue of the problems with your study: Dr. Crocker, as a respected medical professional who is attempting to influence public policy through research, it behooves you to address the concerns raised about that research. I believe you owe it to the community to end your silence on these issues.
1. Mr. Jason Kenney, Canada's 37th Parliament, 1st Session, March 2, 2001
2. How helmet promotion and laws affect cycle use, CycleHelmets.org
3. From the Eugene/Springfield (OR) Bicycle Map (1998?), which further credits the American Lung Association, Oregon Traffic Commission, Association of Commuter Transportation, American Automobile Association, and City of Eugene. Reported at BicycleUniverse.info
4. New Zealand bicycle helmet law-do the costs outweigh the benefits? Taylor M, Scuffham P. 2002. Injury Prevention: 2002;8:317-320
5. CycleHelmets.org, graph on home page
6. Drivers give unhelmeted cyclists less room, Reuters, Sept. 12, 2006
7. Head injuries rising despite bike helmets, Julian Barnes, New York Times, July 29, 2001
8. The Dr. Patrick J. Crocker letter, Patrick Goetz, League of Bicycling Voters, October 2006
9. Traffic safety facts 1996: Pedalcyclists, U.S. Dept. of Transportation
10. No justice for cyclists, BicycleAustin.info
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