| Bicycle Helmet |
Article Index for Bicycle |
Website Links For Bicycle |
Information AboutBicycle Helmet |
| CATEGORIES ABOUT BICYCLE HELMET | |
| cycling equipment | |
| helmet | |
| cycling | |
| helmets | |
| safety clothing | |
| cycling safety | |
|
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 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. 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 (no current Bell brand helmet is Snell certified, some Specialized ones are – the Snell Memorial Foundation website includes a list of certified helmets). 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. Most of the standards are designed to be passable using current designs and materials rather than to set a certain minimum safety standard. Tests typically involve weighting the helmets and dropping them onto anvils with flat, Hemispherical and cornered (comparable to a Kerb stone) shapes. Since the hemispherical and cornered anvils present the most difficult tests to pass, they are tested with a shorter drop, although there is no reason in practical riding why a person falling onto a flat surface would not fall as far as someone hitting a round object. Design and materials There are two main types of helmet: hard shell and soft/micro shell (no-shell helmets are now rare). In both types Impact Energy is absorbed as a stiff foam liner is crushed, up to the point where the liner is crushed to its minimum thickness, or the helmet shatters, after which no further energy is absorbed. Collision energy varies with the square of impact Speed : a typical helmet will absorb the energy of a fall from a bicycle, an impact speed of around 12mph or 20 km/h. It will only reduce the energy of a 30 mph or 50 km/h impact to 27.5 mph or 45 km/h, and even this will be compromised if the helmet fails. This energy calculation is based on the standards, which take no account of the weight of the rider's body, which may be a factor in headfirst falls. As a subsidiary effect they also spread point impacts over a wider area of the skull. Hard shell helmets 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 will reduce superficial injuries to the scalp. Hard shell helmets can also reduce the likelihood of penetrating impacts although these are very rare. The key component of most modern bicycle helmets is a layer of Expanded Polystyrene (EPS), essentially the plastic Foam material used to make inexpensive picnic coolers. This material is sacrificed in an accident, being crushed as it absorbs a major impact. Bicycle helmets should always be discarded after any accident. Helmets are most effective in straight line, or linear, blows to the head at moderate speed. Helmets are not well designed to deal with high speed impacts or rotational stresses (crashes that are not centred, and involve rotation of the head). They are not designed to provide adequate protection for a collision involving another moving vehicle, (e.g. a car). A common misunderstanding is to assume that a broken helmet has prevented some serious injury. Helmets are designed to crush without breaking; EPS absorbs little energy in brittle failure and once it fails no further energy is absorbed. To prevent breakage, the foam in the helmets is reinforced inside with plastic netting to keep the foam together. Proper fit It is important that a helmet should fit the cyclist properly – according to research most helmets (well over 90% Parkinson et al. (2003) PEDIATRICS Vol. 112 No. 2:320–323 ) have been 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 Rivara et al. (1999) Injury Prevention 5: 194-197 . Most manufacturers provide a range of sizes ranging from Child ren'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. 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. History Prior to the mid- 1970s , 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 of where cycles were regarded as children's toys, 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 (EPS) 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, 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. Atmos helmet, showing seamless in-mould microshell construction.]] 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. Helmet regulations 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. DEATH OF CYCLIST ANDREI KIVILEV: DECLARATION BY THE INTERNATIONAL CYCLING UNION 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 being the first major race affected. The 2003 rules allowed for discarding the helmets during final climbs of at least 5 kilometres in length;http://www.uci.ch/english/news/news_2002/20030502i.pdf 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 Are helmets needed? Do helmets work? Desirable effects of helmet use |
|
|