Dear Ms Mulady:
As a bike advocate and alternative transportation activist I was somewhat disappointed by your recent article on the proposed all-ages MHL for Seattle cyclists. I have certainly seen worse media coverage; your article was less biased than many. Nevertheless I think you could have shown a bit less favour towards the helmet industry and its sales force, and given cyclists more of a fair shake.
I apologise for sending you such a long response, but I find that it often takes rather a lot of words, statistics, facts etc. to counteract popular misconceptions and soundbites. Issues in road safety and public health are not as simple as we wish they were. I hope you'll bear with me, and that an informed critique of your article will be of some interest. I have included a list of references [at end] which cover most of the major points raised in the text.
The first thing that struck me was that the most vivid description of a cyclist, and the first encountered in your text, is of a young man doing bike stunts off-road, in a park. A "cartoon" or representative image is thus immediately established: the typical cyclist (or the typical unhelmeted cyclist) is a daredevil (also male, and youthful). The reader who only skims the article may come away with an unfortunate stereotype reinforced rather than challenged.
You are perhaps not aware of an important statistic: a motor vehicle is "involved" in over 90 percent of US cyclist fatalities where the cyclist is of college age and younger. This figure drops to "merely" 80 to 85 percent for older cyclists. Vanishingly few cyclist fatalities happen in parks, in single-vehicle (bike) accidents -- even while stunting. These would qualify as freak accidents, not typical cycling risk. Opening your article with an implicit definition of cyclists as daredevils, and of maximum cycling risk as self-inflicted (e.g. stunting in parks) rather than imposed (e.g. by motor vehicles or careless driving) is unrepresentative, and likely to mislead the uninformed reader.
A tacit assumption runs through the article, that the efficacy of plastic helmets in preventing brain injury and death in cyclists is proven beyond a doubt and therefore warrants no discussion. This is certainly what the manufacturers and retailers of sports helmets of every kind would like the public to believe -- though they are not willing to warrant or guarantee their product in any way, and they disclaim all liability in the event of customer injury or fatality while wearing a helmet. Certainly there is a consensus among the traditional authorities on road safety in the US, that bicycles are a problem and helmets are the answer.
Both these premises are being challenged regularly in less traditional, more progressive journals and conferences on public health and road safety. Controversy still smoulders in the 30-year-old debate over helmet design and efficacy. A larger-scale debate continues over road danger reduction strategy in general. I refer you to the published works of John Franklin, Mayer Hillman, John Adams, Robert Davis, Malcolm Wardlaw, and many other new-school "contrarians" challenging old models and theories of road safety developed in the 50's and 60's.
Presumably because of this tacit assumption that the case is closed and the verdict is in, the only evidence your article offers in support of the efficacy of helmets is purely anecdotal. One rider with a helmet damaged after a fall asserts that she would probably be dead or disabled had she not been wearing it. The number of persons making this assertion in any given year (sometimes in print) is enormous -- tens of people in every city in the US, every year, at least. It is so often repeated that the fact of repetition increases public acceptance; but ironically, the perennial popularity of this anecdote is what makes the claim less than credible.
The tally of these anecdotal "prevented deaths" is so large that, were all these claims justified, cycling would be unimaginably dangerous: each year, thousands of deaths would have been narrowly avoided only by wearing a helmet. If this were the case, then we would expect the annual statistics for cyclist death and disability in the early 1980's, prior to organised helmet promotion and uptake, to have been appalling. Since helmets were not yet prevalent and most cyclists rode "unprotected", all these "prevented deaths" we hear about today would not have been prevented back then -- during an era when road cycling was more popular than it is today and off-road cycling had not yet been popularised.
There should therefore have been an annual slaughter of cyclists which suddenly tapered off just as helmets gained popularity -- a reduction of fatality by something like a factor of 5, if claims such as those in the 1987 Thompson, Rivara and Thompson paper are to be taken seriously. In fact, there has not been any such enormous, strongly marked change in the annual figures for cyclist death on US roads corresponding neatly with the period of maximum helmet takeup by the cycling population. There has been instead a slow, steady decline in fatality per million population for all groups of road users over the last 40 years.
Oddly enough, the steady decline in road fatality rates for juvenile cyclists in particular (those most likely to wear helmets mandated by juvenile MHLs [mandatory helmet laws]) mirrors uncannily the steady decline in road fatality for juvenile pedestrians, to a correlation coefficient of .985 between the years 1975-1999 (FARS data). If the decline in juvenile cyclist fatality is due to helmet acceptance -- as helmet industry marketers claim -- then what accounts for the exactly parallel decline in juvenile pedestrian fatality? A close relationship between these two trends is also seen in data from the UK, Canada, New Zealand and Australia.
A recent British Medical Journal paper suggests a possible solution: our assessment of the efficacy of mechanical interventions in general -- helmets for cyclists and motorcyclists, air bags, seat belts and similar devices for drivers -- may have been confounded by enormous improvements in medical technology and response times over the same period. The gradual decline in road fatalities and permanent disablities per million population in wealthy industrialised nations such as the US, might have as much to do with post-crash care -- major advances in surgical techniques and emergency room procedures -- as with preventing injury in the first place.
Recent experience in Florida tends to support this new theory; when Florida repealed its adult helmet law for motorcyclists, many "safety experts" predicted a massive die-off of Florida bikers. In reality, motorcyclist fatality statistics did not suddenly rise; this casts some doubt on the absolute effectiveness of motorcycle helmets in preventing crash deaths. (Note that motorcycle helmets are far heavier and sturdier, therefore presumably more effective, than flimsy bike helmets).
It is not necessary to claim the unprovable/unlikely, i.e. that helmets never do any good at all, in order to query whether their efficacy is so overwhelmingly demonstrated that it makes social and political sense to force citizens to purchase and wear them. More than an unsubstantiated anecdote is required, to demonstrate this efficacy.
Another tacit assumption of the article is that cyclist mortality is a large and urgent public safety problem, one which warrants an "emergency" response such as legislating public behaviour. We do not normally legislate people's safety and health choices except under conditions immediately threatening to the social fabric. No one gets a ticket for not brushing their teeth, in other words; and we only require mass vaccinations when there is a risk of epidemic and lethal infectious disease. What is the scope of the "cycling safety problem"?
You may not be aware that only about 700-800 cyclists perish each year on US roads, most of them killed by collision with motor vehicles. While only the most callous person could assert that seven or eight hundred deaths per annum are irrelevant, the figure is dwarfed by other on-road fatality statistics, which in turn are dwarfed by other mortality statistics.
For perspective, about 5,000 pedestrians die each year in the US after being hit by motor vehicles. In a typical year, more than 30,000 persons die on American roads while inside motor vehicles during a crash. These numbers have risen just a bit in recent years, with the introduction and popularity of heavy, unwieldy SUVs which inflict higher lethality on other vehicle occupants in a crash [and curiously, are also about twice as likely as "regular" cars to run over the owner's own child in a driveway]. In all these categories, as indeed with any kind of fall or crash, lethality is often from serious brain injury. It is a type of trauma to which all mammals are vulnerable, and whose effects are quick enough to challenge even modern rapid-response emergency medical services.
Every year 40,000 or so Americans "die by car" one way and another (only 750 of them cyclists), out of 2.5 million (2,500,000) deaths per annum. 150,000 deaths per annum are classified as "untimely," i.e. resulting from violence or mishap, and the largest single causal category of these is "car crash" -- which claims more American victims annually than suicide, homicide, diabetes, or AIDS. If you are under 45 and male, an automobile crash is more likely to truncate your natural lifespan than cancer, heart disease, or other frightening medical prospects.
As you can see, the humble bicycle barely figures in this picture. But perhaps it has a niche market in head injuries?
Some analysts estimate that there are 75,000 to 100,000 deaths in the US from head injury every year. From the amount of fuss made over cycle helmets, we would expect that a large proportion of these are cyclists -- an epidemic of cyclist fatality from head trauma. But in fact cyclists represent only about .6 to .9 percent (.006 to .009) of these deaths. Estimates of the number of hospitalisations for various severities of head injury in an average year range from 500,000 to 750,000. Cyclists represent only from 1 to 1.5 percent of these hospitalisations (even though about 6 percent of Americans cycle regularly).
We might now ask ourselves why there is such a conviction in the public mind that cycling poses a pre-eminent risk of head injury and HI related death, when the contribution of cyclists to national HI stats is so small. Is there, in fact, a public health problem so large and urgent that it warrants legislative interference with the individual's private choice?
Ironically, the leading single cause of head injury and related fatality for Americans of all ages is, once again, "car crash"; the largest single group of persons hospitalised for head injury are drivers or passengers in a motor vehicle at the time of injury.
Your article tacitly reinforces the incorrect assumption that cycling is a major contributor to head injury and head injury fatality, and that government intervention is urgently needed to deal with a "crisis".
The major "crises" which CDC have recently reported are crises of diet and lifestyle. Several CDC reports in the last two years have been urgent and alarmist in tone, but not about cyclist injury. They are alarmed about physical unfitness and unhealthy diet for Americans in general, and particularly for young Americans and those in lower income brackets. One contributory cause of unfitness is lack of exercise, and one reason for lack of exercise is a marked decline in walking and cycling over the last 40 years. Children in particular hardly walk or cycle at all any more. Far from being a major threat to public health, cycling offers a remedy for what CDC currently considers a genuine crisis in American public health.
It is quite legal to do many other far more dangerous things than helmetless cycling. Here "more dangerous" means: actuarially speaking, far more likely to cause premature death. These other dangerous activities inflict enormous annual health care costs on the nation as a whole. High-risk activities include eating at McDonald's, smoking, leading a sedentary lifestyle, or driving a car (particularly a SUV). The British researcher Mayer Hillman analysed national mortality statistics and concluded that regular cycling (even on busy roads, even without a helmet) was 20 times more likely to improve health and extend life than to curtail it. One has to wonder why cyclists are singled out for coercive "public health" legislation, when such factors as habitual physical inactivity, automobile-related trauma, poor diet and smoking cost us many, many more person-years of lost life and productivity.
I am disappointed that your article does not raise these important questions.
In light of the national road fatality stats -- which hold fairly steady from one year to the next -- the "public good" argument for MHL seems to be equally applicable to pedestrians and car occupants. We have already noted that far more people die on the road as pedestrians or car occupants, and that head injury is common in all categories of road fatality. If bike-style helmets are effective as claimed, then surely a much larger number of deaths per year could be prevented if these other road users were also required by law to wear protective headgear.
I assume that, like most Americans of adult years, you are a frequent if not habitual driver, and an occasional pedestrian. Humour me for a moment and consider seriously the idea of being required by law to strap on a styrofoam helmet every time you get in your car -- or every time you leave your house to walk to the corner store as an "at-risk" pedestrian. This may help you to understand the resistance of many everyday utility cyclists to all-ages MHL.
Your article quotes a source to the effect that wearing a helmet is just like wearing a seat belt. To test the validity of this assertion, I suggest that aside from considering your own reaction, you try asking a random sample of motorists of your acquaintance how they would feel about having to wear a bike helmet while driving (or face a $40 ticket). I think their resistance to the idea will be fairly strong; but most of them are probably not annoyed by wearing seat belts. Seat belts are less intrusive and uncomfortable than a helmet. They do not feel like being forced to wear a uniform, nor do they destroy hairstyles or cause the head and face to sweat.
Safety research organisations have suggested more than once in the last 20 years that motorists should wear helmets, since about half of all dead car occupants die of major head injury. The suggestion has always been dismissed with laughter: "people would not stand for it." It seems to me another interesting question for discussion: why do we expect cyclists to "stand for it," but not drivers or car passengers?
With regard to cyclists, the argument is occasionally made that "if even one life can be saved" it is worth any amount of legislation, police harassment, ticketing, etc. Surely this argument applies with much greater force to the much higher numbers of pedestrian and MV occupant fatalities. Yet the argument is never applied to these fatalities. Why is that? This is an interesting social/political question which your article does not raise.
Your article uncritically quotes a source to the effect that that all-ages MHL are an intrinsic part of bike promotion and support for alternative transportation -- that it is "silly" to promote cycle use, yet not make helmets compulsory.
I suggest that the most successful cycling culture in the industrialised West is Holland, where from 20 to 25 percent of citizens habitually use a bike for daily trips to work, as well as for entertainment and shopping (in the US, only about 6 percent of the population cycles regularly, and in many cases this is only for recreation, not utilitarian daily travel). The Netherlands also has the lowest helmet-wearing rate of any industrialised, automobile-equipped nation, and one of the finest safety records for cyclists. Germany has a very low rate of helmet wearing, a high rate of cycling, and a cyclist safety record far superior to that of the US. There is no natural or logical connection between promoting cycling and cyclist safety, and promoting helmet sales. The two are quite independent and may actually be incompatible.
Why incompatible? Here we should consider the experience of Australia and New Zealand, where the passage of all-ages MHL was followed by an immediate and measurable drop in cycling, especially among young people. Official counts of cyclists did not rebound to pre-law levels in Western Australia until many millions of tax dollars had been spent, over almost a decade, on special cycling facilities projects to entice people back onto their bikes. In that same period, the population increased by 15 percent and the price of gasoline went up by almost 50 percent; this might make us wonder why cycling levels were not significantly higher than they had been 9 years earlier instead of merely recovering. The recovery of cyclist numbers also coincided with a trend for local enforcement to become laxer and more sporadic, so that helmetless cyclists were not persecuted with the zeal which initially accompanied the new law.
Despite a marked reduction in the number of cyclists, the imposition of helmet wearing, and the building of many cycle paths in the 1990s, cyclist injuries and admissions to Western Australian hospitals rose to new highs during the late 1990s.
Is there any reason to suppose that by reducing the number of cyclists on the road we may actually increase the risk to each individual cyclist and see a rise rather than a fall in the incidence of cyclist injury? There is, in fact, a small but growing body of research which suggests strongly that the more cyclists there are on the roads, the safer each individual cyclist is. Cyclists appear to be at greater risk where cycling is unpopular.
Any legislation which reduces the number of cyclists on the road (as the MHL did in Australia and New Zealand) is likely to increase risk for the remaining cyclists. This may be one explanation for the curious results from some jurisdictions where government has invested considerable effort and expense into passing and enforcing MHLs for cyclists, only to find that injury rates per thousand cyclists actually rise after passage of the law.
Your article implies that Seattle is lagging behind the times, that it is somehow old-fashioned or backwards in not imposing all-ages MHLs similar to those adopted by surrounding jurisdictions. Perhaps you are not aware of the experience of Austin TX, which repealed its all-ages MHL for cyclists after an unsatisfactory experience.
Seattle and its environs appear, from a national perspective, to be repeating an error which another major US city has already tried and recovered from, and which has cost other national governments large sums and many years to recover from, setting back the progress of cycling advocacy and alternative transport by a decade or more.
Your article asserts that helmets are cheap and readily available. It does not mention the manufacturers' requirement that a new helmet must be purchased every 5 years, or after any impact, to maintain efficacy.
To purchase a $50 helmet once is perhaps not burdensome, at least for the fully employed. But to repurchase it after any fall (or after dropping it accidentally down a flight of steps) and to replace it every 5 years, becomes (by comparison with other bike maintenance expenses which for most casual cyclists are nearly zero) a noticeable financial burden. Most people never replace their helmets unless the helmet is completely destroyed -- which, according to the manufacturers, means that millions of people are riding bicycles while wearing helmets no longer in usable condition and unable to protect them properly.
Since we are encouraged (perhaps even legally required) to believe the manufacturers' advertising claims without reservation as regards the saving power of helmets, should we also be required to accept without skepticism their guidelines for product use and lifetime? Should we empower our police to stop cyclists and check the year of manufacture of their helmets, inspect the helmets for damage, and issue "fix it" tickets directing the individual to purchase a new one if the helmet is too old or looks scuffed or cracked? To what extent would our police then become a strong-arm sales force for a private industry?
Would this be a good use of valuable police time? It seems a bit ridiculous. And yet, if riding with a 20-year-old helmet incorrectly fitted and loosely attached is sufficient to avoid a ticket -- and the manufacturer asserts that such a helmet does not offer protection -- then what point is there in the law?
Your article -- by omission, selection, and implication -- suggests strongly that all the forces of reason, adulthood, and science are marshalled behind the helmet law. It suggests that the only objections to the law are based on libertarian principles, or on youthful fecklessness/rebelliousness. There is no sugggestion of the lively, on-going, international academic and political controversy over road safety, engineering interventions, "car-centric" policy, cycling safety, and related topics. The issue is presented as one between rebellious, foolish individuals and sensible, benign experts who know best.
In fact, there are several grounds for skepticism about the desirability of MHL -- aside from sincere libertarianism. Large-sample long-period studies pre- and post-MHL in several countries (US, CA, NZ, AU) do not demonstrate a strong "helmet effect," or a social/fiscal benefit commensurate with the social/fiscal costs of enforcement; conversely, repeal of helmet laws does not result in a strong increase in fatalities; there are no systematic fatality/injury differences between US states with MHL and those without; there is documentary evidence that the imposition of all-ages MHL does reduce ridership and defeat efforts to promote cycling; there are jurisdictions where cyclist injuries have increased after passage of MHLs; enforcement unfortunately often turns out to be selective and to involve race and class profiling; and last but perhaps most importantly, the singling out of cyclists for coercive "public health" legislation (as if they were a disease vector that needed controlling) is irrational and unjustified in the face of very low contribution to HI and HI mortality.
What is important about this last point is that this singling-out is discriminatory, and tends to reinforce negative social attitudes towards cyclists and cycling. It is a very short step, in soundbite terms, from believing that cycling is so dangerous that one needs a "hard-hat" to do it, and believing that cycling is so dangerous that no one should do it. I know many people who do not cycle because they fear imminent death every time they venture out on two wheels without the protection of a car around them. This exaggerated fear of cycling is a product of biased media coverage, as well as of misguided (imho) official "road safety" efforts.
Unfortunately, your article reinforces this fear and promotes the incorrect popular notion that ordinary street cycling is terribly dangerous, that it is particularly dangerous as a likely source of major head injury, and that therefore all sensible people should wear special protective headgear at all times when participating in such a dangerous activity. This "dangerising" of cycling is one of the greatest barriers to public acceptance of and participation in this benign form of daily transport.
An associated problem is the overselling of the bike helmet as a "life saving device". Manufacturers' advertising campaigns often imply nearly magical saving powers to helmets. Slogans and advertising posters often imply that by wearing the vendor's product, the cyclist is guaranteed safety despite the most reckless manoeuvres in the most dangerous conditions. The overselling of helmets and the construction of excessive faith in their limited impact-mitigating ability, can lead to two negative (endangering) results.
One is that the individual cyclist, particularly the young male demographic at highest risk for all forms of accident and injury, will ride even more recklessly because of a belief that merely wearing a helmet is sufficient to keep him safe from any permanent harm. We do not publicise or discuss the number of helmeted cyclists who are killed or suffer permanent or lasting injuries, and a mythology has been built up (with the active collusion of the helmet manufacturers and retailers) that only unhelmeted cyclists die or suffer serious injury. This is not the case. Cyclists also die while wearing helmets.
The still-controversial but well-attested theory of "risk compensation" or "risk homeostasis" suggests that where people have a strong sense of security or protection, they "consume" that sense of security by behaving more boldly and riskily, until an individual, personally comfortable level of risk has been attained. The overselling of helmets and the exaggeration of their protective effects may result in more dangerous, less cautious riding.
The second problem which results from overselling and product hype, is that adults and authorities begin to believe that their responsibility to juvenile cyclists begins and ends with forcing kids to wear a helmet. Very little emphasis has been placed in the last 20 years on teaching young cyclists basic cycling skills and road law. Many parents do not teach their children to cycle on roads at all, but encourage them to ride on the sidewalk (which is, ironically, more dangerous). As a result we have many adult and young-adult cyclists on the road today who are completely ignorant of road law, and are lacking in fundamental cycling skills.
Motorists are also "let off the hook" by the overemphasis on helmets -- rather than making motorists observe appropriate safety precautions on roads shared with cyclists, we encourage motorists to think that the only danger to cyclists comes from "not wearing a helmet," and that motorists have no responsibility for cyclist safety. Since we know that the majority of dead cyclists have been bounced off (or dragged under, or crushed by) a motor vehicle, it is inappropriate to allow motorists to believe that putting helmets on cyclists is all that's required to address the problem of road danger. Motorists must take responsibility for the potential lethality of their chosen mode of transport.
The overselling of helmets encourages an abdication of responsibility by educators, parents, road safety authorities and motorists.
Finally, I would like to mention two related thinking points.
One is directly relevant. A racing cyclist crashed while riding unhelmeted this year, and died; immediately, there was an outcry for requiring helmet use in all future races, as "he would be alive today if only he had been wearing a helmet." This same season, two other racing cyclists have died in race crashes, while wearing helmets. No one asked why the helmets did not, as advertised and promoted, save these lives. No one asked whether these two dead cycling athletes might have ridden a bit less recklessly if they had not had such absolute faith in the saving power of their helmets -- a faith built over the last three decades of intensifying helmet advertising and promotion.
As well as asking ourselves how many lives the helmet industry has saved, we should perhaps ask ourselves how many lives an exaggerated faith in helmet efficacy may have cost. In the last decade we have seen many exposés of ways in which major industries mislead the public in order to boost sales, even at the expense of public health. I think it is time we turned our consumer skepticism and ethical spotlight on the plastics industry and the helmet industry.
My second thinking point relies on analogy. Suppose we suggest that all women should be required to wear veils or observe curfews -- to "protect" them "for their own good" from male violence or harassment. By this proposal we would be withdrawing moral and social scrutiny from the actions of the men who harass or assault. We would enforce restrictions and requirements upon the more vulnerable citizen, rather than curbing the behaviour of the stronger, more powerful, or more aggressive.
When we suggest that all cyclists should be required to wear helmets because of road danger, we withdraw our moral and social scrutiny from the causes of road danger. We allow ourselves to forget that the pre-eminent source of road danger is the automobile. We allow ourselves to forget that excessive automobile-dependence is an urgent social, economic, and public health problem, imposing many direct and indirect social costs in addition to our 40,000+ road fatalities per annum. We encourage ourselves to see cycling as a problem, rather than as an elegant and economical solution to the many problems of car-dependence.
The WHO estimates that already, after only a century of motorised transport, motor traffic has become the premiere cause of sudden and untimely death world-wide -- outstripping such venerable competitors as war, suicide, and interpersonal violence. Problems of this magnitude are seldom solved by distracting our attention from the root cause and trying to cover up the symptoms with bandaids, or victim-blaming.
Given the inconclusive results from the imposition of MHL worldwide so far and the difficulty of documenting solid benefits from such laws, the only interest groups which can indubitably be said to benefit from this legislation are the plastics industry, the helmet manufacturers, and the bike accessory retailers. Your article, despite commendable efforts to "represent both sides," still uncritically promotes the interests of these corporate lobbyists rather than dealing seriously with pressing issues of road safety, urban livability, and alternative transportation. This is why I found it disappointing.
I hope I have sparked your interest in alternative points of view and a less car-centric, more pedestrian- and bike-positive way of looking at road danger and strategies for reducing it. Please feel free to visit my web site for other information about car-free living, cycling, hauling cargo by bicycle, etc.
In my opinion it will be a sad day for Seattle if this law is passed, a step backwards rather than forwards in road danger reduction and public safety policy. It will be a shame if media coverage such as your article is instrumental in passing such a retrograde law.
D. A. Clarke
1. Critiques of Thompson, Rivara & Thompson 1987 (a paper on which much of current dogmatic faith in helmet efficacy is based) summarised by cycling expert John Franklin: http://www.lesberries.co.uk/cycling/helmets/seattle.html
2. Juvenile pedestrian vs cyclist fatality trends: unpublished article by Geary and Clarke, 2000: http://www.daclarke.org/AltTrans/posthoc.html
3. British Medical Journal article on the confounding effect of improvements in medical technology and practise: http://bmj.com/cgi/content/full/326/7397/1004/e See also: http://bmj.com/cgi/content/full/313/7067/1239
4. Paper on results of Florida's repeal of motorcyclist helmet law: Stolzenberg and D'Alessio, "Born to be Wild: The Effect of the Repeal of Florida's Mandatory Motorcycle Helmet-Use Law on Serious Injury and Fatality Rates", Evaluation Review Apr 2003. PDF available here.
5. Mortality statistics on US roads: see FARS database online at http://www-fars.nhtsa.dot.gov/ Peculiar risks of SUVs to occupants and non-occupants: http://www.washingtonmonthly.com/features/2001/0212.mencimer.html (a review of Bradsher's High and Mighty), also "SUV owners also have the unfortunate tendency to run over their own children. Twenty percent of children killed by cars are run over in their own driveway, and SUV owners are more than twice as likely to do this than other drivers. That's because the size of the vehicle reduces visibility while backing up. " http://www.charlotte.com/mld/charlotte/news/columnists/dr_traffic/5243275.htm
6. Mortality statistics for US population: various sources including CDC, Laudan's Book of Risks and other readily available references.
7. Contribution of cycling to head injury rates: CDC and Caregiver web sites, cited by K Kifer in essay critiquing MHL: http://www.kenkifer.com/bikepages/advocacy/mhls.htm
8. CDC on juvenile physical unfitness and related syndromes: http://www.cdc.gov/nccdphp/dnpa/kidswalk/pr-kidswalk.htm
9. Cycling risks vs health benefits: "A form of cost-benefit analysis of cycling has been attempted by comparing life years lost through cycle accidents to life years gained through regular exercise. Although a direct quantitative analysis is not possible due to a lack of conclusive data, existing evidence would suggest that, even in the current hostile traffic environment, the benefits gained from regular cycling are likely to outweigh the loss of life through cycling accidents for the current population of regular cyclists." 'Cycling Towards Health and Safety,' British Medical Association, 1992. See also BMJ (Wardlaw): http://bmj.com/cgi/content/full/321/7276/1582 and UK gov't White Paper on cycling and national health: http://www.lcc.org.uk/campaigns/cyclist_safety_health/health_benefits_of_cycling.asp See also Hillman, Mayer, "Cycle Helmets: the Case For and Against", Policy Studies Institute 1993
10. Helmets for drivers: http://www.magma.ca/~ocbc/nigel.html
11. Decline in cyclist numbers in Australia following imposition of MHL: "The year after national helmet law passage in Australia, the bicycle use rate among children (<18 yrs.) decreased 36%." (CDC Morbidity and Mortality Weekly Report, May 14, 1993) See also papers by Robinson, D. L. and data presented at http://www.cycle-helmets.com/
12. Rise in head injuries after MHL: "Head injuries up after helmet law?" David Sands, Edmonton Sun July 12 2003. "Surprising stats suggest bike-accident head injuries have increased since Alberta passed a mandatory helmet law. Figures from nine health regions show a sharp spike in the percentage of bicycle-related head injury cases coming into their emergency wards. And that spike peaks in the six months following the government's mandatory helmet law."
13. Repeal of Austin TX all-ages MHL: http://bicycleaustin.info/ (click on Politics, then Helmet Laws).
14. Risk compensation, failure of helmets to protect as advertised: NYT article, http://www.daclarke.org/AltTrans/BarnesNYT.html Responses and commentaries: http://www.daclarke.org/AltTrans/BarnesIndex.html
15. Racing cyclist deaths this year: Kivilev (unhelmeted), Haruko Fujinawa (helmeted), Garrett Paul Lemire (helmeted). Summary at http://www.magma.ca/~ocbc/
16. WHO on lethality of motor traffic: http://www.who.int/mediacentre/releases/2003/pr40/en/