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Bicycle helmet
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A bicycle helmet is a helmet intended to be worn while riding a bicycle. They are designed to attenuate impacts to the cranium of a cyclist in falls while minimizing side effects such as interference with peripheral vision. The debate on whether helmet use should be compulsory is intense and occasionally bitter, often based not only on differing interpretations of the academic literature, but also on differing assumptions and interests on the two sides.
A cycle helmet should be light in weight and should provide adequate ventilation, because cycling can be an intense aerobic activity which significantly raises body temperature and the head in particular needs to be able to regulate its temperature.
dominant form of helmet was the leather "hairnet" style, mainly used by racing cyclists.
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Encyclopedia
A bicycle helmet is a helmet intended to be worn while riding a bicycle. They are designed to attenuate impacts to the cranium of a cyclist in falls while minimizing side effects such as interference with peripheral vision. The debate on whether helmet use should be compulsory is intense and occasionally bitter, often based not only on differing interpretations of the academic literature, but also on differing assumptions and interests on the two sides.
A cycle helmet should be light in weight and should provide adequate ventilation, because cycling can be an intense aerobic activity which significantly raises body temperature and the head in particular needs to be able to regulate its temperature.
About helmets
History of designs
The dominant form of helmet was the leather "hairnet" style, mainly used by racing cyclists. This offered minimal impact protection and acceptable protection from scrapes and cuts. In countries with long traditions of utility cycling, nearly all cyclists did not and still do not wear helmets. The use of helmet by non-racing cyclists began in the U.S. in the 1970s. After many decades when bicycles were regarded as children's toys only, many American adults took up cycling during and after the bike boom of the 1970s. Two of the first modern bicycle helmets were made by MSR, a manufacturer of mountaineering equipment, and Bell Sports, a manufacturer of helmets for auto racing and motorcycles. These helmets were a spinoff from the development of expanded polystyrene foam liners for motorcycling and motorsport helmets, and had hard polycarbonate plastic shells. The bicycle helmet arm of Bell was split off in 1991 as Bell Sports Inc., having completely overtaken the motorcycle and motor sports helmet business.
The first commercially successful purpose-designed bicycle helmet was the Bell Biker, a polystyrene-lined hard shell released in 1975. At the time there was no appropriate standard; the only applicable one, from Snell, would be passed only by a light open-face motorcycle helmet. Over time the design was refined and by 1983 Bell were making the V1-Pro, the first polystyrene helmet intended for racing use. In 1984 Bell produced the Li'l Bell Shell, a no-shell children's helmet. These early helmets had little ventilation.
In 1985 the Snell B85 was introduced, the first widely-adopted standard for bicycle helmets; this has subsequently been refined into B90 and B95 (see Standards below). At this time helmets were almost all either hard shell or no-shell (perhaps with a vacuum-formed plastic cover). Ventilation was still minimal due mainly to technical limitations of the foams and shells in use.
Around 1990 a new construction technique was invented: in-mould microshell. A very thin shell was incorporated during the moulding process. This rapidly became the dominant technology, allowing for larger vents and more complex shapes than hard shells.
Hard shells declined rapidly among the general cyclist population during the 1990s, almost disappearing by the end of the decade, but remain popular with BMX riders as well as inline skaters and skateboarders.
The late 1990s and early 2000s saw advances in retention and fitting systems, replacing the old system of varying thickness pads with cradles which adjust quite precisely to the rider's head. This has also resulted in the back of the head being less covered by the helmet; impacts to this region are rare, but it does make a modern bike helmet much less suitable for activities such as unicycling, skateboarding and inline skating, where falling over backwards is relatively common. Other helmets will be more suitable for these activities.
Since more advanced helmets began being used in the Tour de France, Carbon Fiber inserts have started to be used to increase strength and protection of the helmet. The Giro Atmos and the Bell Alchera are among the first to use carbon fiber.
Some modern racing bicycle helmets have a long tapering back end for streamlining.
History of standards
In the United States the Snell Memorial Foundation, an organization initially established to create standards for motorcycle and auto-racing helmets, implemented one of the first standards. The American National Standards Institute (ANSI) created a standard called ANSI Z80.4 in 1984. Later, the United States Consumer Product Safety Commission (CPSC) created its own mandatory standard for all bicycle helmets sold in the United States, which took effect in March 1999.
In the European Union (EU) the currently applicable standard is EN 1078:1997.
In the UK the current standard is BS EN 1078:1997, which is identical to the EU standard, and which replaced BS 6863:1989 in 1997.
In Australia and New Zealand, the current standard is AS/NZS 2063:1996. The performance requirements of this standard are slightly less strict than the Snell B95 standard but incorporate a quality assurance requirement. As a result, the AS/NZS can be argued to be safer. However this is not to be confused with the standards marketing program run by SAI Global in which manufacturers pay royalties and fees to afix a "5 ticks" sticker on helmets deemed of suitable standard. The AS/NZS 2063:1996 only requires compliance, and not the optional 5 ticks symbol.
The CPSC and EN1078 standards are lower than the Snell B95 (and B90) standard; Snell helmet standards are externally verified, with each helmet traceable by unique serial number. EN 1078 is also externally validated, but lacks Snell's traceability. The most common standard in the US, CPSC, is self-certified by the manufacturers. It is generally true to say that Snell standards are more exacting than other standards, and most helmets on sale these days will not meet them (currently, Specialized is the only bicycle helmet brand in the world to meet the Snell standard. All of their helmets are Snell certified.)
In 1990 the Consumers' Association (UK) market survey showed that around 90 % of helmets on sale were Snell B90 certified. By their 1998 survey the number of Snell certified helmets was around zero. Hard shells declined rapidly among the general cyclist population over this period, almost disappearing by the end of the decade, but remained more popular with BMX riders as well as inline skaters and skateboarders.
Although helmet standards have weakened over time there is no data on which to base an assessment of how this has affected the design goal of mitigating minor injuries. Minor injuries are substantially under-reported and it is difficult if not impossible to effectively measure such injuries on a meaningful scale.
Helmets exploit two fundamental physical realities in their functioning. Firstly, kinetic energy increases with the square of speed, which means a doubling of speed translates into an injury potentially four times as severe. However, concurrent with this is the need to consider the direction in which the forces act. A cyclist travelling along a horizontal roadway at a given rate of speed will incur a much more severe head injury if he/she flies straight into a solid brick wall than if he/she simply falls and dissipates the kinetic energy by sliding and scraping along the roadway. Two things are key here: the roadway must be clear, with no obstacles to forward sliding on the pavement, and secondly, the helmet must slide without gripping the roadway and exerting rotational forces on the head.
The second fundamental physical reality germane to helmet functioning is embedded in Newton's Second Law, i.e. F=ma (force = mass multiplied by acceleration). Since acceleration is defined as the change in velocity divided by the change in time, what a helmet effectively does is increase the time over which the forces act. Because time is in the denominator, more time equates to a lower peak force exerted on the brain as the head is decelerated by the helmet. And, since velocity is defined as the rate of change of distance per unit time, effectively what this means is that more deceleration distance (i.e. more distance over which deceleration occurs) translates into a gentler deceleration for the brain. (The same fundamental physical principles are exploited in automobiles, where crumple zones and airbags work together to enable people to survive even head-on collisions at highway speeds.)
A helmet's ability to absorb energy could be improved by increasing the volume of expanded polystyrene, but this would make it thicker, heavier, and hotter to wear. Another concern is that a thicker helmet increases the risk of rotational-type brain injuries (discussed in more detail below). Ultimately, every helmet design represents some sort of compromise.
The trend is towards thinner helmets with many large vents. This trend to lower standards has been noted in some of the studies It is relatively common for helmets to fail on test, and some helmets on sale are not certified to any accepted standard. The most widely-cited pro-helmet studies were conducted when most helmets were of a hard-shell construction; these are now rare outside of niche applications such as BMX.
Design intentions and standards
There are two main types of helmet: hard shell and soft/micro shell (no-shell helmets are now rare). Both are intended to reduce acceleration to the head due to impact, as a stiff expanded polystyrene liner is crushed.
Standards involve the use of an instrumented headform which is dropped, wearing a helmet, onto various anvils. The speed of impact is designed to simulate the effect of a rider's head falling from approximately usual riding height, without rotational energy and without impact from another vehicle.
As noted earlier, collision energy varies with the square of impact speed. A typical helmet is designed to absorb the energy of a head falling from a bicycle, hence an impact speed of around 12mph or 20 km/h. This will only reduce the energy of a 30 mph or 50 km/h impact to the equivalent of 27.5 mph or 45 km/h, and even this will be compromised if the helmet fails. As a subsidiary effect, they should also spread point impacts over a wider area of the skull. Hard shell helmets may do this better, but are heavier and less well ventilated. They are more common among stunt riders than road riders or mountain bikers. Additionally, the helmet should reduce superficial injuries to the scalp. Hard shell helmets may also reduce the likelihood of penetrating impacts, although these are very rare.
The above figures assume a standard bicycle with a diamond-framed frame, which places the rider's head roughly 1.5 to 2 metres above ground level. Injury severity from a fall might be less if the cyclist is riding a recumbent-type bicycle, in which the rider reclines and has his/her head about 1 metre from ground level.
Criticism of current standards; new designs
Helmet liners may be too stiff to be effective. Some standards require the use of headforms heavier and more rigid than the human head; these are more capable of crushing foam than is the human head. In real accidents "very little crushing of the liner foam was usually evident... What in fact happens in a real crash impact is that the human head deforms elastically on impact. The standard impact attenuation test making use of a solid headform does not consider the effect of human head deformation with the result that all acceleration attenuation occurs in compression of the liner. Since the solid headform is more capable of crushing helmet padding, manufacturers have had to provide relatively stiff foam in the helmet so that it would pass the impact attenuation test... As the results in Figure 15 illustrate, the child skull is far from being solid and will deform readily on impact. This fact is well known in the medical field and is largely why a child who has had a rather modest impact to the head is usually admitted to hospital for observation. The substantial elastic deformation of the child head that can occur during impact can result in quite extensive diffuse brain damage."
In real accidents, while broken helmets are common, it is extremely unusual to see any helmet that has compressed foam and thus may have performed as intended. “Another source of field experience is our experience with damaged helmets returned to customer service... I collected damaged infant/toddler helmets for several months in 1995. Not only did I not see bottomed out helmets, I didn’t see any helmet showing signs of crushing on the inside.”
A new design of liner, the "cone-head", now being manufactured for motorcycle helmets but not yet available for bicycle helmets, has been designed in response to the 1987 study. It may provide better impact absorption.
Most helmets provide no protection against rotational injury and may make it worse. "The major discovery is that the skull plays an important role in protecting against rotational acceleration," says Phillips. He says almost all head injuries involve not just a direct blow to the skull but also damage to blood vessels caused by the brain rotating within the skull.
In mechanical terms, the head is an elliptical spheroid with a single universal joint, the neck. It is therefore almost impossible to hit it without causing it to rotate. The head tries to dampen these forces using a combination of built-in defences: the scalp, the hard skull and the cerebrospinal fluid beneath it. During an impact, the scalp acts as rotational shock absorber by both compressing and sliding over the skull. This absorbs energy from the impact."
The Phillips head protection system, also only available in motorbike helmets at present, is designed to reduce rotational injury.
Proper fit
It is important that a helmet should fit the cyclist properly – in one study 96 % were found to be incorrectly fitted. Efficacy of incorrectly fitted helmets is reckoned to be much lower; one estimate states that risk is increased almost twofold.
Most manufacturers provide a range of sizes ranging from children's to adult with additional variations from small to medium to large. The correct size is important. Some adjustment can usually be made using different thickness foam pads. Helmets are held on the head with nylon straps, which must be adjusted to fit the individual. This can be difficult to achieve, depending on the design. Most helmets will have multiple adjustment points on the strap to allow both strap and helmet to be correctly positioned. Additionally, some helmets have adjustable cradles which fit the helmet to the occipital region of the skull. These provide no protection, only fit, so helmets with this type of adjustment are unsuitable for roller skating, stunts, skateboarding and unicycling. In general, the more skull coverage a helmet provides, the more effectively it can be fitted to the head and hence the better it will remain on the head in an accident.
The helmet should sit level on the cyclists head with only a couple of finger-widths between eyebrow and the helmet brim. The strap should sit at the back of the lower jaw, against the throat, and be sufficiently tight that the helmet does not move on the head. It should not be possible to insert more than one finger's thickness between the strap and the throat.
Helmet compulsion in cycling sport
Historically, road cycling regulations set by the sport's ruling body, Union Cycliste Internationale (UCI), did not require helmet use, leaving the matter to individual preferences and local traffic laws. The majority of professional cyclists chose not to wear helmets, citing discomfort and claiming that helmet weight would put them in a disadvantage during uphill sections of the race.
The first serious attempt by the UCI to introduce mandatory helmet use in 1991 was met with strong opposition from the riders. An attempt to enforce the rule at the 1991 Paris–Nice race resulted in riders' strike, forcing the UCI to abandon the idea.
While voluntary helmet use in professional ranks rose somewhat in the 1990s, the turning point in helmet policy was the March 2003 death of Kazakh Andrei Kivilev. The new rules were introduced on May 5, 2003, with the 2003 Giro d'Italia being the first major race affected. The 2003 rules allowed for discarding the helmets during final climbs of at least 5 kilometres in length; subsequent revisions made helmet use mandatory at all times.
No studies have been published yet into whether injuries have reduced as a result.
The helmet debate
Is cycling risky enough to require helmets?
There is no one agreed way of presenting risk. Proponents of helmet compulsion may tend to quote figures for the (large) total number of head injuries or injuries of any kind; opponents may be more likely to produce estimates for the (low) risk of serious injury per cyclist. One pro-helmet website gives its "own pick of Basic Numbers from many sources": 773 bicyclists died on US roads in 2006, down just 11 from the year before. 92% (720) of them died in crashes with motor vehicles. About 540,000 bicyclists visit emergency rooms with injuries every year. Of those, about 67,000 have head injuries, and 27,000 have injuries serious enough to be hospitalized. Bicycle crashes and injuries are under-reported, since the majority are not serious enough for emergency room visits. 44,000 cyclists were reported injured in traffic crashes in 2006. In a campaign to make helmets compulsory for child cyclists, it has been stated that "in a three-year period from 2003, 17,786 children aged 14 and under were admitted to NHS hospitals in England because of injuries incurred while cycling"
Overall, cycling is beneficial to health – the benefits outweigh the risks by up to 20:1.. To cycling activists, the major problem with helmet promotion is that in order to present the idea of a "problem" to match the solution they present, promoters tend to overstate the dangers of cycling. This review provides more evidence that safety advocates' obsession with protecting our young cyclists through use of helmets is enormously out of proportion to the low risk involved in cycling. To these advocates, we say, "Cycling is a safe, fun, healthy activity. Stop exaggerating its risks. That discourages the uptake of cycling and from a health point of view is extremely counterproductive."}} Cycling is no more dangerous than being a pedestrian. A UK opponent of compulsion has pointed out that it "still takes at least 8000 years of average cycling to produce one clinically severe head injury and 22,000 years for one death." Ordinary cycling is not demonstrably more dangerous than walking or driving, yet no country promotes helmets for either of these modes. "The inherent risks of road cycling are trivial... Six times as many pedestrians as cyclists are killed by motor traffic, yet travel surveys show annual mileage walked is only five times that cycled; a mile of walking must be more "dangerous" than a mile of cycling..." The proportion of cyclist injuries which are head injuries is essentially the same as the proportion for pedestrians at 30.0 % vs. 30.1 %.
Are helmets useful? Desirable effects of helmet use
No randomized controlled trials have been done on the subject. The evidence comes from two main types of observational study. Most of the literature that mentions helmets refers back to a small number of these studies, rather than itself providing primary evidence. Overall, according to CTC, the UK's national cyclists organisation, "the evidence currently available is complex and full of contradictions, providing at least as much support for those who are sceptical as for those who swear by them."
Time-trend analyses
Time-trend analyses compare changes in helmet use and injury rates in populations over time, most validly where helmet laws have resulted in large changes in a short time. Potential weaknesses of this type of study include: simultaneous changes in the road environment (e. g. drink-drive campaigns); inaccuracy of exposure estimates (numbers cycling, distance cycled etc.), changes in the definitions of the data collected, failure to analyse control groups, failure to analyse long-term trends, and the ecological fallacy.
Robinson's review of cyclists and control groups in jurisdictions where helmet use increased by 40 % or more following compulsion concluded that "enforced helmet laws discourage cycling but produce no obvious response in percentage of head injuries". Some of the data for this publication is available at . This study has been the subject of vigorous debate. Authors do not agree on how studies should be selected for analysis, nor on what summary statistics are most relevant. A more recent review, by Macpherson and Spinks, includes two original papers (neither of which meet the criteria for inclusion in Robinson's review) and concludes that "Bicycle helmet legislation appears to be effective in increasing helmet use and decreasing head injury rates in the populations for which it is implemented. However, there are very few high quality evaluative studies that measure these outcomes, and none that reported data on an (sic) possible declines in bicycle use."
There are many other studies. The largest, covering eight million cyclist injuries over 15 years, showed no effect on serious injuries and a small but significant increase in risk of fatality. Although the head injury rate in the US rose in this study by 40 % as helmet use rose from 18 % to 50 %, this is a time-trend analysis with the potential weaknesses mentioned above; the correlation may not be causal. Association with increased risk has been reported in other studies. Different analyses of the same data can produce different results. For example, Scuffham analysed data on the increase of voluntary wearing in New Zealand to 1995; he concluded that, after taking into account long-term trends, helmets had no measurable effect. His subsequent re-analysis without accounting for the long-term trends suggested a small benefit. Scuffham's later cost-benefit analysis of the New Zealand helmet law showed that the cost of helmets outweighed the savings in injuries, even taking the most optimistic estimate of injuries prevented.
Case-control studies
Known potential problems with this type of study design include confounding (attributing benefits from unmeasured differences in behavior to differences in helmet choice), and recall bias (people incorrectly reporting helmet use).
Such studies consistently find that cases of head injury report a lower rate of helmet-wearing than controls who have injured other parts of the body. This has been taken as strong evidence that cycle helmets are beneficial in a crash. The most widely-quoted case-control study, by Thompson, Rivara, and Thompson, reported an 85 % reduction in the risk of head injury by using a helmet. There are many criticisms of this study, including use of a control group with very different risks. Re-analysis of the Thompson, Rivara and Thompson data, substituting helmet wearing rates from co-author Rivara's contemporaneous street counts, reduces the calculated benefit to below the level of statistical significance. This has been taken as evidence of confounding. In another study, helmet users also seemed to be protected against severe injuries to the lower body; "helmet non-use is strongly associated with severe injuries in this study population. This is true even when the patients without major head injuries are analyzed as a group". It is possible that at least some of the 'protection' afforded helmet wearers in previous studies may be explained by safer riding habits rather than solely a direct effect of the helmets themselves.
Other case-control studies exist, all showing similar results. In Victoria, Australia, during 1977-1980, bicyclist casualties, then unhelmeted, sustained head injuries including severe head injuries, more than twice as frequently as the helmeted motorcyclist casualties.
Anecdotal evidence
A common misunderstanding is to assume that a broken helmet has prevented some serious injury. "the main impact was to my head. So much so, that my helmet broke in two (as it is designed to do). Without the helmet, it would have been my head that was broken and I wouldn’t be writing this blog entry! I’d be dead..."
Helmets are designed to crush without breaking; expanded polystyrene absorbs little energy in brittle failure and once it fails no further energy is absorbed. "cracks developing partly or fully through the thickness of the foam-slab renders it useless in crushing and absorbing impact forces" To prevent overt fragmentation, the foam in most helmets is reinforced inside with plastic netting to keep the foam together even after cracking.
Are helmets harmful? Undesirable effects of helmet use
Concerns have been raised that mandatory bicycle helmet laws lead to a reduction in the number of cyclists, and increased helmet use may lead to increased risks.
Less bicycle use
When mandatory bicycle helmet laws were enacted in Australia, slightly more than one third of bare-headed cyclists ceased to ride their bicycles frequently. The reduction in the number of cyclists is likely to harm the health of the population more than any possible protection from injury. The long term health benefits of bicycle use are many-fold and extensively documented, and so any reduction in bicycling will likely have a negative impact on the overall health of a population. It has been suggested that a fall in the number of bicyclists in the 1990s may reflect an increase of in-line skating or other recreational activities, or the evidence that helmet promotion deters cycling has been simply denied.
A reduction in cycling may lead to an increased risk for the cyclists remaining on the road, due to a "safety in numbers" effect. According to one source, the probability of an individual cyclist being struck by a motorist declines with the 0.6 power of the number of cyclists on the road. This means that if the number of cyclists on the road doubles, then the average individual cyclist can ride for an additional 50% of the time without increasing the probability of being struck. It is thought that the increased frequency of motorist-cyclist interaction creates more aware motorists.
Several mechanisms by which cycle helmet promotion or compulsion may deter cycling have been suggested. Helmets and their promotion may reinforce the misconception that bicycling is more dangerous than traveling by passenger car. Referring to the use of "human skull" images in a campaign, the CTC suggests that "this macabre imagery, with its associations of hospitals and death, is likely to reduce cycle use, thereby undermining efforts to realise the health and other benefits of increased cycling". Bicycle helmets cost money and may make cycling less convenient; they are bulky and often cannot be stored securely with bikes. However, a well-designed bicycle helmet can last for a good number of years, if it is not involved in an accident. Both the shell and the polystyrene liner will deteriorate with protracted exposure to ultraviolet light (from sunlight), which means that helmet lifespan is much more a function of hours worn rather than years elapsed since the date of manufacture. Since fluorescent indoor lighting also contains some ultraviolet rays, it is appropriate to store a helmet in a dark location. Similarly, when a bicycle is parked outdoors, it is wise to take the helmet indoors for storage.
Bicycle helmets are seen as incompatible with some hairstyles, forcing bicycle users to recreate their hairstyle after each journey. Finally, bicycle helmets and other "safety" equipment have, in the past, occasionally been seen as vexatious and ridiculous.
For example, in the 2006 film The Benchwarmers, the character Clark—played by Jon Heder—sports a bicycle crash helmet as an accessory prop to highlight his lack of social skills and physical coordination.
Risk compensation
A range of theories have been proposed to explain why helmet use might cause more or worse accidents.
Under the risk compensation theory, helmeted cyclists may be expected to ride less carefully; this is supported by evidence for other road safety interventions such as seat belts and anti-lock braking systems. There is some evidence for risk compensation by children in relation to safety equipment. Anecdotally, many riders report feeling safer with a helmet: "When I wear it, I feel safe..."
Motorists may also alter their behaviour towards helmeted cyclists. Recent evidence from England found that vehicles passed a helmeted cyclist with measurably less clearance (8.5 cm) than that given to the same cyclist unhelmeted (out of an average total passing distance of 1.2 to 1.3 metres).
Rotational injury
Rotational injury "is unleashed when the helmet ricochets along the road, twists sharply and the brain rotates within the skull, causing blood vessels and neurons to rip apart throughout the substance of the brain. Quite often there may be no obvious superficial damage – especially if the rider is wearing a conventional helmet. The damage is done within." The major causes of permanent intellectual disablement and death after head injury may be torsional forces leading to diffuse axonal injury (DAI), a form of injury which usual helmets cannot mitigate and may make worse. Helmets may increase the torsional forces by increasing the distance from the centre of the spine to the outside of the helmet, compared to the distance to the scalp without a helmet: "Bicycle helmet crash simulation experiments carried out as part of this project indicated very high rotational accelerations for a fall over the handlebars at 45 km/h. The rotational accelerations were found to be 30 percent higher than those found in similar tests using a full face polymer motorcycle helmet." Accordingly, compared to a traditional bicycle helmet, a bicycle helmet of full-face design would be expected to bring an added margin of safety in the form of reduced rotational forces exerted on the brain. This is in addition to the direct facial protection and greatly improved retention security provided by such a helmet design. However, full-face bicycle helmets are uncommon in the general cycling population, despite the advent of well-ventilated designs.
The shell material of the helmet plays a key role in enabling the helmeted head to slide along a surface (e.g. a roadway surface). Harder shells are less likely to be gripped by a rough surface, and might therefore be less likely to impart massive rotational forces to the brain. However, the major determinants of the rotational forces on the brain are the details of the accident itself -- that is, the magnitude and location of the forces exerted on the helmet and transmitted to the head inside it.
Positions and arguments
Much of the research is partisan in one way or another. Rodgers re-analysed data which supposedly showed helmets to be effective; he found data errors and methodological weaknesses so serious that in fact the data showed "bicycle-related fatalities are positively and significantly associated with increased helmet use". One report concluding that helmet use was associated with a 60 % reduction in injuries was found to be in error due to a simple statistical error; correcting the error results in a claimed efficacy of 186 %; despite this the authors continue to assert that the results stand. A report commissioned by the UK Government was supportive of cycle helmet promotion but dismissed much of the contradictory evidence with minimal examination, and the principal authors were associated with a programme of the Child Accident Prevention Trust (CAPT), which is strongly pro-helmet. Curnow, author of papers on helmets and traumatic brain injury, has also published criticism of pro-helmet research.
Supporters
Many notable organisations and individuals believe that a helmet can reduce head injuries, and even save a cyclist's life. The World Health Organisation promote the use of helmets as a strategy for preventing head injuries caused by bicycle crashes or falls. Use of cycling helmets is supported by numerous groups in the United States, including the American Medical Association and the American National Safety Council. By 1991, the League of American Wheelmen described bicycle helmets as a "Mom and apple pie" issue in the US. In 2004 the British Medical Association's Board of Science and Education adopted a position calling on the UK government to introduce cycle helmet legislation, and this was confirmed at the 2005 Annual Representative Meeting following fifteen minutes of debate. The prominent U.S.-based cycling activist John Forester suggests that helmet wearing could save 300 deaths a year in the US, behind Effective Cycling at 500 and ahead of all other interventions, totalling 1,030.
Opponents
Amongst those who do not support the arguments in favor of helmet use, or helmet compulsion, are many notable academics, practitioners and cyclists' lobbying groups. Robinson reviewed data from jurisdictions where helmet use increased following legislation, and concluded that helmet use did not demonstrably reduce cyclists' head injuries. Mayer Hillman, a transport- and road safety-analyst from the UK, does not support the use of helmets, reasoning that they are of very limited value in the event of a collision with a car, that risk compensation negates their protective effect and because he feels their promotion implicitly shifts responsibility of care to the cyclist. He also cautions against placing the recommendations of surgeons above other expert opinion in the debate, comparing it to drawing conclusions on whether it is worthwhile to buy lottery tickets by sampling only a group of prizewinners. The prominent UK-based cycling activist John Franklin is skeptical of the merits of helmets, regarding proactive measures including bike maintenance and riding skills as being more important. Cyclists' representative groups complain that focus on helmets diverts attention from other issues which are much more important for improving bicycle safety, such as road danger reduction, training, roadcraft, and bicycle maintenance. Of 28 publicly funded cycle safety interventions listed in a report in 2002, 24 were helmet promotions. For context, one evaluation of the relative merits of different cycle safety interventions estimated that 27 % of cyclist casualties could be prevented by various measures, of which just 1 % could be achieved through a combination of bicycle engineering and helmet use.
In 1998 the European Cyclists' Federation adopted a position paper rejecting compulsory helmet laws as being likely to have greater negative rather than positive health effects. The UK cyclists' club, CTC, believes that the "overall health effects of compulsory helmets are negative." The UK minister of transport knew of no evidence to support the claim that helmets saved lives. The British National Children's Bureau has said "The 2004 BMA statement announcing its decision to support compulsory cycle helmets shows how the uncritical use of accident statistics can lead to poor conclusions." The same report estimated that, at most, universal helmet use would save the lives of three children aged 0 to 15 each year. That figure "assumes universal and correct use of helmets, it assumes that risk compensation does not occur and it assumes that no children die as a result of strangulation or other injuries caused by helmet use. These assumptions are most unlikely to be correct in the real world."
Influencing helmet use
There is a long-running argument over the use, promotion, and compulsion of cycle helmets. Helmet use has increased significantly in many, but not most, jurisdictions since the 1980s, primarily because of helmet promotion and compulsion laws. Most heated controversy surrounds laws making helmet use compulsory.
Promotion
Significant helmet promotion preceded epidemiological studies evaluating the effectiveness of bicycle helmets in bicycle crashes.
Received opinion in some English-speaking countries is that bicycle helmets are useful and that every cyclist should wear one; helmets had become a ‘?“Mom and apple pie” issue’ in the United States by 1991 according to the League of American Bicyclists. Professional bodies elsewhere have agreed, such as the Swiss Council for Accident Prevention. The Dutch Institute for Road Safety Research (SWOV) advocates helmet use and helmet laws to further improve cycling safety. This is not the only view in the Netherlands; a pro-cycling paper states: "The Dutch cycling experts and planners interviewed for this paper adamantly opposed the use of helmets, claiming that helmets discourage cycling by making it less convenient, less comfortable, and less fashionable. They also mention the possibility that helmets would make cycling more dangerous by giving cyclists a false sense of safety and thus encouraging riskier riding behavior."
Dismissing concerns in 1996 that helmets should be shown to actually reduce injury rates, two pro-helmet doctors asked "How robust must the evidence be when the benefits of wearing helmets are so patently obvious? What is the downside to wearing a helmet, other than the mussing of Minerva's hair?". One of these, himself a cyclist, started his "career of advocacy" in 1972 and is now editor of an academic journal on injury prevention.
In this position he has found "tiresome" academic argument that helmet wearing is useless.
Rivara was already engaged in surveying and lobbying for helmet use before the influential Thompson, Rivara and Thompson case-control study was commenced in 1989, while the report by Thompson, Rivara and Thompson for the Cochrane review has been criticised for being dominated by their own work.
Promotion of helmets raises further issues. Bell, the major helmet manufacturer, supports both helmet promotion and legislation.
Legislation
The following countries have mandatory helmet laws, in at least one jurisdiction, for either minors only, or for all riders: Australia, Canada, Finland, Iceland, Israel, Sweden, USA, and New Zealand. In the U.S. 37 states have mandatory helmet laws. Although the link is not causal, it is observed that the countries with the best cycle safety records (Denmark and the Netherlands) have among the lowest levels of helmet use. Their bicycle safety record is generally attributed to public awareness and understanding of cyclists, safety in numbers, education, and to some extent separation from motor traffic.
A study of cycling in major streets of Boston, Paris and Amsterdam illustrates the variation in cycling culture: Boston had far higher rates of helmet-wearing (32 % of cyclists, versus 2.4 % in Paris and 0.1 % in Amsterdam), Amsterdam had far more cyclists (242 passing bicycles per hour, versus 74 in Paris and 55 in Boston). Cycle helmet wearing rates in the Netherlands and Denmark are very low. An Australian journalist writes: "Rarities in Amsterdam seem to be stretch-fabric-clad cyclists and fat cyclists. Helmets are non-existent, and when people asked me where I was from, they would grimace and mutter: "Ah, yes, helmet laws." These had gained international notoriety on a par with our deadly sea animals. Despite the lack of helmets, cycling in the Netherlands is safer than in any other country, and the Dutch have one-third the number of cycling fatalities (per 100,000 people) that Australia has." The UK's CTC say that cycling in the Netherlands and Denmark is perceived as a "normal" activity requiring no special clothing or equipment.
See also
Case studies
- Thompson, R., Rivara, F. and Thompson, D. (1989), A Case-Control Study of the Effectiveness of Bicycle Safety Helmets, New England Journal of Medicine, 25 May, 320:21, 1361–67 — (The most widely cited pro-helmet study.)
- Scuffham Trends in cycle injury in New Zealand under voluntary helmet use, Langley. Accident Analysis and Prevention, Vol 29:1, 1997 — (Showed no benefit from large-scale increases in helmet use.)
- FT McDermott, JC Lane, GA Brazenor & EA Debney. The effectiveness of bicyclist helmets: a study of 1710 casualties. J Trauma, Vol 34, pp834-845, 1993.
Risk
- John Adams, 1995, Risk, Routledge, ISBN 1-85728-068-7 — (Authoritative reference on risk compensation theory.)
Compulsion Laws
- BikeBiz (industry journal), , March 24, 2006
- BikeBiz (industry journal), , Feb 27th 2006
- D Hendrie, M Legge, D Rosman, C Kirov, , Road Accident Prevention Research Unit, Department of Public Health, The University of Western Australia.
- Merton, R.K., "The Unanticipated Consequences of Purposive Social Action", American Sociological Review, Vol.1, No.6, (December 1936), pp. 894–904. (see Unintended consequence)
- Scuffham, Alsop, Cryer, Langley, "Head Injuries to Cyclists and the New Zealand Cycle Helmet Law", Accident Analysis and Prevention, 2000, 32: 565–573
- Vulcan, A.P., Cameron, M.H. & Heiman, L., "Evaluation of mandatory bicycle helmet use in Victoria, Australia", 36th Annual Conference Proceedings, Association for the Advancement of Automotive Medicine, Oct 5–7, 1992.
- Vulcan, A.P., Cameron, M.H. & Watson, W.L., "Mandatory Bicycle Helmet Use: Experience in Victoria, Australia", World Journal of Surgery, Vol.16, No.3, (May/June 1992), pp. 389–397.
- McDermott, F.T., "The Effectiveness of helmet wearing on reducing bicyclist head injuries and mandatory legislation in Victoria, Australia. Annals of the Royal College of Surgeons of England. 1995; 77:38-44.
External links
- —from RoSPA
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- John Franklin,
- Chris Gillham,
- The Vehicular Cyclist,
- Randy Swart,
- Snell Memorial Foundation,
- U.S. Consumer Product Safety Commission,
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- (spoof, ostensibly pro-compulsion, site)
- BikePortland.org,
- Cykelhjelm.org -
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