A motorcyclist wearing full safety clothing of helmet, gloves, boots and leathers
To improve motorcycle safety many developed countries mandate the wearing of protective clothing by motorcyclists, especially a helmet. Other protective gear may include certain types of jackets, gloves, boots, and pants. Jackets meant for motorcyclists are typically made of nylon, leather, or Kevlar. These jackets typically include heavy padding on the elbow, spine, and shoulder regions. Gloves are generally made of leather or Kevlar and some include carbon fiber knuckle protection. Boots, especially those for sport riding, include reinforcement and plastic caps on the ankle and toe areas. A well-protected motorcyclist will wear boots with heels that fit on motorcycle pegs and provide good ankle support. Pants are usually leather, nylon, or Kevlar. Except for helmets, none of these items are required by law in any state in the U.S. but are recommended by many of those who ride.
"Off road" riders wear a range of plastic armour to protect against injury from falling off, hitting other riders and bikes, debris kicked up from the rear wheel of leading bikes, and from running into track barriers protecting the public. This armour protects the extremities from breakage and dislocation and the back and chest from strain and broken bones. Although fairly efficient, it is of course not always completely effective. Many riders wear "roost protectors" designed specifically to protect against painful debris from other bikes, but are of no use in a fall or collision.
Leathers
The term "motorcycle leathers" describes leather clothing worn by motorcyclists. Leathers provide impact, puncture and abrasion protection to a rider who falls from his or her bike, and provide additional weather protection beyond what normal clothing offers when travelling at high speed. The most common leather used for motorcycle apparel is cowhide, known for its strength and durability. Kangaroo leather is becoming popular for its suppleness, light weight and strength compared with cowhide.
Originally, motorcycle leathers were adapted from tank corps gear immediately following World War I. Duster coats, which tended to catch in the wheels, were switched for short coats. Wide-pegged breeches were worn by some motorcycle police (and are still worn in Belgium) and by dispatch riders in World War II, but were largely abandoned in the post-war years because of their association with certain Nazi uniforms.
Currently there are two major styles of motorcycle leathers: the tight fitting and sometimes colorful one or two piece suits based on motorcycle racing leathers; and the somewhat looser fitting leather trousers and jackets, usually black and often decorated with metal studs and tassles. The latter style, the jackets in particular, are also worn by people who are fond of the style but do not ride motorcycles. The classic American Perfecto motorcycle jacket with epaulets and diagonal zipper, made famous by Marlon Brando in The Wild One, (1954) was invented in 1928 by Irving Schott, of Schott NYC in New York City. Leather chaps, adapted from cowboy gear, were used by American bikers starting in the early 1960s.
A lot of modern leathers have armour on the inside at critical impact points such as elbows, shoulders, knees and the spine. The armour ranges from high density foam to foam backed hard armour, and in Europe much of it is CE marked. It is designed to spread the impact point to minimize injury.
Textile clothing
Increasingly, motorcyclists are choosing protective equipment constructed of man-made textiles rather than leather due to their improved weather protection, from heat, cold and water, and the increased utility these garments tend to provide in terms of pockets and vents. Common materials include high density (600 - 1000 Denier) ballistic nylon (e.g., Cordura) and Kevlar (or blends of Kevlar, Cordura, and Lycra) and often include waterproof liners made from materials such as Goretex. These artificial fabrics are said by some motorcyclists to be more comfortable, particularly in warm weather. The textile garments typically take less time to dry out, whereas leather gear may remain wet (and cold) for some time.
Textile protective clothing is also nearly always worn over ordinary clothing, whereas leather suits—particularly those manufactured for racing—are not. In addition, synthetic fabrics generally provide better protection from inclement weather. For these reasons, synthetics are often practical for commuters and can help make motorcycles an attractive alternative to four wheeled vehicles.
Not all textile clothing is made from synthetic materials. Heavy weight waxed cotton was used for many years before the development of modern materials, typified by the jackets made by companies such as Belstaff.
Performance claims range for textile motorcycle clothing from somewhat less to somewhat better than competition grade leathers. Key elements of performance include:
strength - the protective clothing must maintain its integrity in the event of a crash
abrasion resistance ability to slide instead of grabbing tarmac or concrete (grabbing would tumble the rider, likely resulting in greater injury) heat resistance - whilst sliding the friction with the road can result in enough heat to melt many synthetic materials
ability to stretch and breathe (for comfort). Additional protection may be provided by armour (CE approved is desirable) and airbag systems.
Proper fit
Whatever materials one chooses for one's motorcycle gear, it is important to get the correct fit when purchasing it. Incorrectly fitted garments may result in excessive injury if armour shifts out of position during a riding mishap. Flapping due to too loose a fit also creates unnecessary wear and tear, wind drag, and noise, and can distract the rider. In the event of a fall, loose garments may grab the road surface, resulting in a tumble rather than a slide. Two piece suits often come with zips to join the jacket and trousers/jeans together, thus improving safety in the event of a crash.
Boots
Motorcycle boots are a type of protective footwear used by motorcycle riders designed to protect a rider's feet and legs while riding and in the event of a crash. Sturdy, over-the-ankle boots can protect from a variety of riding hazards. Boots with oil-resistant, rubber-based composite soles will give you a strong grip on the pavement and help you keep your feet on the pegs. If the boots have heels, they should be low and wide to provide a stable base when standing with the bike. In case of a crash, boots help provide valuable protection against foot and ankle injuries. As with jackets and pants, boots should be designed specifically for motorcycling, using materials (thick leather, abrasion resistant textiles and plastics) that can protect against the forces of a crash.
Engineer boots
Wesco crotch-high Engineer Boots
Similar to harness boots, engineer boots are a type of motorcycle boot: footwear usually worn by motorcycle riders, commonly called "bikers." The boots are most often made of heavy weight black leather, have a rounded toe and range in height from short (10") to extra high (38"). The most typical height is between 10 and 18 inches.
Engineer boots are designed to protect the motorcycle rider from injury to the foot and leg in the case of an accident while riding and to prevent burns of the rider's calves while riding. They may include a built-in steel toe cap and metal shank in the heel, and often are double layered with leather for stiffness. Engineer boots typically have an adjustable leather strap across the ankle as well as an adjustable leather strap at the top of the shaft to adjust the fit. Multiple straps at the top of the shaft are also not uncommon. Soles and heels are
usually made of hard rubber and may either be relatively flat or may have lugs for increased traction.During the depression era, Chippewa Shoe Company[1], of Chippewa Falls, Wisconsin, developed a pair of boots with stovepipe leg and was fashioned over "English Riding Boot" last. In the 1960s, Sears carried the Sears branded Chippewa Engineers and showed them as worn by land surveyors, a possibility as of how the name came about.[2] Another major manufacturer of Engineer Boots is West Coast Shoe Company based in Portland, Oregon. They began manufacturing the engineer boot in 1939. A large portion of their sales began with the shipbuilders in Portland, Oregon, building ships for World War II
Motocross boots
Motocross boots are a variety of motorcycle boot designed specifically for off-road, motocross (MX) or all-terrain vehicle riding. To help prevent a rider's feet and legs from being injured, motocross boots are typically much more stiff than regular motorcycle boots or racing boots, but are more flexible than ski boots by comparison.
Modern motocross boots are usually nearly knee-high (about 16 inches in height) and made from a combination of leather, metal, plastic and/or man-made composite materials to create a very form-fitting, comfortable and tight boot. To allow a rider to easily get the boot on or off, the shaft of a motocross boot is designed to open lengthwise. Multiple adjustable straps (usually 4 to 5) are deployed along the foot, ankle and shaft of the boot to allow the rider to tighten the boot to his/her preferences and comfort. Some manufacturers also include an internal quick-lacing system between a soft inner leg and the outer harder shell of the boot shaft to further ensure a tight, but comfortable fit. To protect the leading edge of the boot sole against rough terrain, a metal plate is usually screwed in place. The heal of a motocross boot is typically very low: not more than 1/2-inch. A curved plastic or composite plate covers the shin of the boot to protect the rider from debris that may be thrown from the front wheel of the motorcycle.
The most common colors of motocross boots are black or white, but other colors such as red, blue, yellow and green (possibly combined with black or white) are also available. Trick riders often opt to wear white boots since they are more most readily visible.
Racing boots
Similar totouring boots, racing boots are a variety of motorcycle boot designed specifically for riding a motorcycle on hard pavement (either the street or a race track) and are usually between 10 and 14 inches in height and made from a combination of leather, metal, plastic and/or man-made composite materials to create a form-fitting, but comfortable boot. The amount of armored protection provided by racing boots is usually greater than touring boots due to the increased potential for injury at the high speeds needed for racing.
Depending upon how form-fitting the boot is, to allow a rider to easily get the boot on or off, the shaft may be designed to open lengthwise. If so, Velcro is typically used on the inner sides of the opening to allow the rider to close the boot over the foot, ankle and leg. This allows for some flexibility for the rider to control the boot's tightness. Some manufacturers also include an internal quick-lacing system between a soft inner leg and the harder outer shell of the boot shaft to further ensure a tight, but comfortable fit. The heel of a racing boot is typically very low: not more than 1/2-inch, and sole of the heel and foot is typically rather smooth. A curved plastic or composite plate may be included to cover the shin of the boot to protect the rider's shin.
The most common color of racing boots is black, but other colors such as white, red, blue, yellow and green may be combined with black or each other in some fashion. Typical street riders may prefer all black, but racers may opt for a color combination that matches the rest of their motorcycle leathers, helmet and/or motorcycle.
Touring boots
Similar to racing boots, touring boots are a variety of motorcycle boot designed specifically for riding a motorcycle on hard pavement, but with less armored protection than racing boots since they are intended for riders that typically ride on city streets and highways, not race tracks. They are usually between 10 and 14 inches in height and made from a combination of leather, metal, hard rubber, plastic and/or man-made fabrics to create a form-fitting, but comfortable boot.
Dependingupon how form-fitting the boot is, to allow a rider to easily get the boot on or off, the shaft may be designed to open lengthwise. If so, velcro is typically used on the inner sides of the opening to allow the rider to close the boot over the foot, ankle and leg. This allows for some flexibility for the rider to control the boot's tightness. Some manufacturers also include an internal quick-lacing system between a soft inner leg and the harder outer shell of the boot shaft to further ensure a tight, but comfortable fit. The heel of a touring boot is typically very low: not more than 1/2-inch, and sole of the heel and foot is typically rather smooth.
Unlike racing boots that are available in a wide variety of bright colors (as well as black), touring boots are typically only black
Helmet
Two white motorcycle helmets,full face and open face.Use of the colour white helps increase visibility.
A motorcycle helmet is a type of protective headgear used by motorcycle riders. The primary goal of a motorcycle helmet is motorcycle safety - to protect the rider's head during impact, thus preventing or reducing head injury or saving the rider's life. Some helmets provide additional conveniences, such as ventilation, face shields, ear protection, intercom etc. Helmets can have some inconveniences, such as being hot, heavy, or itchy.
Laws and standards
Motorcycle helmets greatly reduce injuries and fatalities in motorcycle accidents, thus many countries have laws requiring acceptable helmets to be worn by motorcycle riders. These laws vary considerably, often exemptingmopeds and other small-displacement bikes. In some countries, most notably the USA, there is some opposition to compulsory helmet useWorldwide, many countries have defined their own sets of standards that are used to judge the effectiveness of a motorcycle helmet in an accident, and define the minimal acceptable standard thereof. Among them are:
AS 1698 (Australia)
CSA CAN3-D230-M85 (Canada)
JIS T8133 (Japan)
NZ 5430 (New Zealand)
ECE 22.05 (Europe)[1][2]
BS 6658:1985 (UK)
DOT FMVSS 218 (USA)[3]
The Snell Memorial Foundation has developed stricter requirements and testing procedures for motorcycle helmets with racing in mind, as well as helmets for other activities (e.g. drag racing, bicycling, horseback riding), and many riders in North America consider Snell certification a benefit when considering buying a helmet while others note that its standards allow for more force (g's) to be transferred to a rider's head than the DOT standard.[4] A motorcycle helmet with either standard will nonetheless provide vastly more protection than one with neither.
In the United Kingdom the Auto-Cycle Union (ACU) defines a stricter standard for racing than the legal minimum BS 6658:1985 or ECE 22.05 specification. Only helmets with an ACU Gold sticker are allowed to be worn in competition, or at track days. Many riders in the UK choose helmets with an ACU Gold sticker for their regular on-road use.
Basic types
There are four basic types of motorcycle helmets. All of these types of helmets are secured by a chinstrap, and their protective benefits are greatly reduced, if not eliminated, if the chin strap is not securely fastened so as to maintain a snug fit.
From most to least protective, the helmet types are:
Full face
A full face helmet covers the entire head, with a rear that covers the base of the skull, and a protective section over the front of the chin. Such helmets have an open cutout in a band across the eyes and nose, with a plastic face shield (which may be clear or tinted) that generally swivels up and down to allow access to the face. Many full face helmets include vents to increase the airflow to the rider.
The significant attraction of these helmets is their protectiveness. Some critics dislike the increased heat, sense of isolation, lack of wind, and alleged reduced hearing of such helmets. Full face helmets intended for off-road use sometimes omit the face shield but extend the visor and chin portions.
Studies have shown that full face helmets offer the most protection to motorcycle riders because 35% of all crashes showed major impact on the chin-bar area Wearing a helmet with less coverage eliminates that protection — the less coverage the helmet offers, the less protection for the rider.
A subset called "Convertible", "Modular", "Flip-face" or "Flip-up" is also available; in these helmets, the chin bar pivots upwards (or, in some cases, may be removed). The rider may thus eat or drink without unfastening the chinstrap and removing the helmet.
Off-Road/Motocross
The motocross and off-road helmet has clearly elongated chin and visor portions, a chin bar, and partially open face to give the rider extra protection while wearing goggles. The visor is to keep the sun out of the eyes of the rider when he or she goes off jumps. The open face is to give the rider extra visibility for obstacles on the track.
Open face
This helmet's rear also covers the back of the skull, but lacks the lower chin armor of the full face helmet, as well as the face shield. Many offer visors of selectable length, some clear, some tinted, which may be used by the rider to block out sunlight or headlights. An open face helmet provides the same rear protection as a full face helmet, but little protection to the face, even from non-crash events. Bugs, dust or even wind to the face and eyes can cause rider discomfort or injury. As a result, it is not uncommon for riders to wear wrap-around sunglasses or goggles to supplement eye protection with these helmets.
Half helmet
The half helmet, also referred to as a "shorty", has essentially the same front design as an open face helmet but with a raised rear. The half helmet provides the minimum coverage generally allowed by law in the US. As with the open face, it is not uncommon to augment this helmet's eye protection through other means. Unlike open face and full face helmets, half helmets are also prone to shifting and sometimes coming off of the rider's head during an accident.
Others
There are other types of headwear - often called "beanies" or "novelty helmets" (a term which arose since they can not legally be called "motorcycle helmets") - which are not certified and generally only used to provide the illusion of compliance with mandatory helmet laws. Such items are often smaller and lighter than DOT-approved helmets, and are unsuitable for crash protection because they lack the energy-absorbing foam that protects the brain by allowing it to come to a gradual stop during an impact. A "novelty helmet" can protect the scalp against sunburn while riding and - if it stays on during a crash - might protect the scalp against abrasion, but it has no capability to protect the skull or brain from an impact.
Visibility
Although black helmets are popular among motorcyclists, they offer the least visibility to motorists. A rider wearing a plain white helmet rather than a black one reduces his or her chance of collision by 24%[6][7] because it is so much more visible — day or night. Nevertheless, black helmets — as shown in the photo of an open-face helmet above, right — outsell white ones (photo, right) by 20:1. Helmets of other colors vary in the visibility they provide to motorists by where they fall on a scale from black to white.
Construction
Laws and standards
Motorcycle helmets greatly reduce injuries and fatalities in motorcycle accidents, thus many countries have laws requiring acceptable helmets to be worn by motorcycle riders. These laws vary considerably, often exemptingmopeds and other small-displacement bikes. In some countries, most notably the USA, there is some opposition to compulsory helmet useWorldwide, many countries have defined their own sets of standards that are used to judge the effectiveness of a motorcycle helmet in an accident, and define the minimal acceptable standard thereof. Among them are:
AS 1698 (Australia)
CSA CAN3-D230-M85 (Canada)
JIS T8133 (Japan)
NZ 5430 (New Zealand)
ECE 22.05 (Europe)[1][2]
BS 6658:1985 (UK)
DOT FMVSS 218 (USA)[3]
The Snell Memorial Foundation has developed stricter requirements and testing procedures for motorcycle helmets with racing in mind, as well as helmets for other activities (e.g. drag racing, bicycling, horseback riding), and many riders in North America consider Snell certification a benefit when considering buying a helmet while others note that its standards allow for more force (g's) to be transferred to a rider's head than the DOT standard.[4] A motorcycle helmet with either standard will nonetheless provide vastly more protection than one with neither.
In the United Kingdom the Auto-Cycle Union (ACU) defines a stricter standard for racing than the legal minimum BS 6658:1985 or ECE 22.05 specification. Only helmets with an ACU Gold sticker are allowed to be worn in competition, or at track days. Many riders in the UK choose helmets with an ACU Gold sticker for their regular on-road use.
Basic types
There are four basic types of motorcycle helmets. All of these types of helmets are secured by a chinstrap, and their protective benefits are greatly reduced, if not eliminated, if the chin strap is not securely fastened so as to maintain a snug fit.
From most to least protective, the helmet types are:
Full face
A full face helmet covers the entire head, with a rear that covers the base of the skull, and a protective section over the front of the chin. Such helmets have an open cutout in a band across the eyes and nose, with a plastic face shield (which may be clear or tinted) that generally swivels up and down to allow access to the face. Many full face helmets include vents to increase the airflow to the rider.
The significant attraction of these helmets is their protectiveness. Some critics dislike the increased heat, sense of isolation, lack of wind, and alleged reduced hearing of such helmets. Full face helmets intended for off-road use sometimes omit the face shield but extend the visor and chin portions.
Studies have shown that full face helmets offer the most protection to motorcycle riders because 35% of all crashes showed major impact on the chin-bar area Wearing a helmet with less coverage eliminates that protection — the less coverage the helmet offers, the less protection for the rider.
A subset called "Convertible", "Modular", "Flip-face" or "Flip-up" is also available; in these helmets, the chin bar pivots upwards (or, in some cases, may be removed). The rider may thus eat or drink without unfastening the chinstrap and removing the helmet.
Off-Road/Motocross
The motocross and off-road helmet has clearly elongated chin and visor portions, a chin bar, and partially open face to give the rider extra protection while wearing goggles. The visor is to keep the sun out of the eyes of the rider when he or she goes off jumps. The open face is to give the rider extra visibility for obstacles on the track.
Open face
This helmet's rear also covers the back of the skull, but lacks the lower chin armor of the full face helmet, as well as the face shield. Many offer visors of selectable length, some clear, some tinted, which may be used by the rider to block out sunlight or headlights. An open face helmet provides the same rear protection as a full face helmet, but little protection to the face, even from non-crash events. Bugs, dust or even wind to the face and eyes can cause rider discomfort or injury. As a result, it is not uncommon for riders to wear wrap-around sunglasses or goggles to supplement eye protection with these helmets.
Half helmet
The half helmet, also referred to as a "shorty", has essentially the same front design as an open face helmet but with a raised rear. The half helmet provides the minimum coverage generally allowed by law in the US. As with the open face, it is not uncommon to augment this helmet's eye protection through other means. Unlike open face and full face helmets, half helmets are also prone to shifting and sometimes coming off of the rider's head during an accident.
Others
There are other types of headwear - often called "beanies" or "novelty helmets" (a term which arose since they can not legally be called "motorcycle helmets") - which are not certified and generally only used to provide the illusion of compliance with mandatory helmet laws. Such items are often smaller and lighter than DOT-approved helmets, and are unsuitable for crash protection because they lack the energy-absorbing foam that protects the brain by allowing it to come to a gradual stop during an impact. A "novelty helmet" can protect the scalp against sunburn while riding and - if it stays on during a crash - might protect the scalp against abrasion, but it has no capability to protect the skull or brain from an impact.
Visibility
Although black helmets are popular among motorcyclists, they offer the least visibility to motorists. A rider wearing a plain white helmet rather than a black one reduces his or her chance of collision by 24%[6][7] because it is so much more visible — day or night. Nevertheless, black helmets — as shown in the photo of an open-face helmet above, right — outsell white ones (photo, right) by 20:1. Helmets of other colors vary in the visibility they provide to motorists by where they fall on a scale from black to white.
Construction
Modern helmets are constructed from plastics. Premium price helmets are sometimes reinforced with kevlar or carbon fiber. They generally have fabric and foam interiors for both comfort and protection. Motorcycle helmets are generally designed to break in a crash (thus expending the energy otherwise destined for the wearer's skull), so they provide little or no protection after their first impact. Note that impacts may, of course, come from things other than crashing, such a dropping a helmet, and may not cause any externally visible damage. For the best protection, helmets should be replaced after any impact, and every three or so years even if no impact is known to have occurred.
Function
This article may requirecleanup to meet Wikipedia's quality standards.Please improve this article if you can.(December 2006)
The conventional motorcycle helmet has two principal protective components: a thin, hard, outer shell typically made from polycarbonate plastic, fiberglass, or Kevlar and a soft, thick, inner liner usually made of expanded polystyrene or polypropylene foam. The purpose of the hard outer shell is:
to prevent penetration of the helmet by a pointed object that might otherwise puncture the skull, and
to provide structure to the inner liner so it does not disintegrate upon abrasive contact with pavement. This is important because the foams used have very little resistance to penetration and abrasion.
The purpose of the foam liner is to crush during an impact, thereby increasing the distance and period of time over which the helmet stops and reducing its deceleration.
To understand the action of a helmet, it is first necessary to understand the mechanism of head injury. The common perception that a helmet's purpose is to save the rider's head from splitting open is misleading. Skull fractures are usually not life threatening unless the fracture is depressed and impinges on the brain beneath and bone fractures usually heal over a relatively short period. Brain injuries are much more serious. They frequently result in death, permanent disability or personality change and, unlike bone, neurological tissue has very limited ability to recover after an injury. Therefore, the primary purpose of a helmet is to prevent traumatic brain injury while skull and face injuries are a significant secondary concern.
The most common type of head injury in motorcycle accidents is closed head injury, meaning injury in which the skull is not broken as distinct from an open head injury like a bullet wound. Closed head injury results from violent acceleration of the head which causes the brain to move around inside the skull. During an impact to the front of the head, the brain lurches forwards inside the skull, squeezing the tissue near the impact site and stretching the tissue on the opposite side of the head. Then the brain rebounds in the opposite direction, stretching the tissue near the impact site and squeezing the tissue on the other side of the head. Blood vessels linking the brain to the inside of the skull may also break during this process, causing dangerous bleeding.
Another hazard, susceptibility of the brain to shearing forces, plays a role primarily in injuries which involve rapid and forceful movements of the head, such as in motor vehicle accidents. In these situations rotational forces such as might occur in whiplash-type injuries are particularly important. These forces, associated with the rapid acceleration and deceleration of the head, are smallest at the point of rotation of the brain near the lower end of the brain stem and successively increase at increasing distances from this point. The resulting shearing forces cause different levels in the brain to move relative to one another. This movement produces stretching and tearing of axons (diffuse axonal injury) and the insulating myelin sheath, injuries which are the major cause of loss of consciousness in a head trauma. Small blood vessels are also damaged causing bleeding (petechial hemorrhages) deep within the brain.
It is important that the liner in a motorcycle helmet is soft and thick so the head decelerates at a gentle rate as it sinks into it. Unfortunately, there is a limit to how thick the helmet can be for the simple reason that the helmet quickly becomes impractical if the liner is more than 1–2 inches (2.5–5 cm) thick. This implies a limit to how soft the liner can be. If the liner is too soft, the head will crush it completely upon impact without coming to a stop. The liner is a hard plastic shell and beyond that is whatever the helmet is hitting, which is usually an unyielding surface, like concrete pavement. Consequently, the head cannot move any further, so after crushing the liner it comes suddenly to an abrupt stop, causing high accelerations that injure the brain.
Therefore, an ideal helmet liner is stiff enough to decelerate the impacting head to an abrupt stop in a smooth uniform manner just before it completely crushes the liner and no stiffer. The required stiffness depends on the impact speed of the head, which is unknown at the time of manufacture of the helmet. The result is that the manufacturer must choose a likely speed of impact and optimize the helmet for that impact speed. If the helmet is in a real impact that is slower than the one for which it was designed, it will still help but the head will be decelerated a little more violently than was actually necessary given the available space between the inside and outside of the helmet, although that deceleration will still be much less than what is would have been in the absence of the helmet. If the impact is faster than the one the helmet was designed for, the head will completely crush the liner and slow down but not stop in the process. When the crush space of the liner runs out, the head will stop suddenly which is not ideal. However, in the absence of the helmet, the head would have been brought to a sudden stop from a higher speed causing more injury. Still, a helmet with a stiffer foam that stopped the head before the liner crush space ran out would have done a better job. So helmets help most in impacts at the speeds they were designed for, and continue to help but not as much in impacts that are at different speeds. In practice, motorcycle helmet manufacturers choose the impact speed they will design for based on the speed used in standard helmet tests. Most standard helmet tests use speeds between 4 and 7 m/s (9 and 16 mph).
Standards testing
Most motorcycle helmet standards use impacts at speeds between 4–7 m/s (9–16 mph) At first glance, this is confusing given that motorcyclists frequently ride at speeds higher than 20 m/s (45 mph). This confusion is relieved by understanding that the perpendicular impact speed of the helmet is usually not the same as the road speed of the motor cycle and that the severity of the impact is determined not only by the speed of the head but also by the nature of the surface it hits. For example, the surface of the road is almost parallel to the direction the motorcyclist moves in so only a small component of his velocity is directed perpendicular to the road while he is riding. Of course, other surfaces are perpendicular to the motorcyclist's velocity, such as trees, walls and the sides of other vehicles. The other vital factor in determining the severity of an impact is the nature of the surface struck. The sheet metal wall of a car door may bend inwards to a depth of 7.5–10 cm (3–4 inch) during a helmeted head impact, meaning that it generates more stopping distance for the rider's head than the helmet itself. So a perpendicular impact against a flat steel anvil at 5 m/s (11 mph) might be about as severe as a 30 m/s (67 mph) oblique impact against a concrete surface or a 30 m/s perpendicular impact against a sheet metal car door or windscreen. Overall, there is a very wide range of severity in the impacts that could conceivably happen in a motorcycle impact. Some of these are more severe than the impacts used in the standard tests and some are less so.
The speeds are chosen based on modern knowledge of the human tolerance for head impact, which is by no means complete. It is possible to deduce how well the 'perfect' helmet outlined in the Function section of this page would perform in an impact of a given severity. If currently available data suggest that the rider is unlikely to survive in such an impact, regardless of how well his helmet performs, then there is little point in demanding that helmets be optimized for this impact. On the other hand, if an impact is so mild that the rider is unlikely to be injured at all so long as he is wearing a helmet than that impact is not a demanding test. Modern standards setters choose the severity of the standard test impact to be somewhere between these two extremes, so that manufacturers are doing their best to protect the riders who can be helped by their helmet during a head impact.
Function
This article may requirecleanup to meet Wikipedia's quality standards.Please improve this article if you can.(December 2006)
The conventional motorcycle helmet has two principal protective components: a thin, hard, outer shell typically made from polycarbonate plastic, fiberglass, or Kevlar and a soft, thick, inner liner usually made of expanded polystyrene or polypropylene foam. The purpose of the hard outer shell is:
to prevent penetration of the helmet by a pointed object that might otherwise puncture the skull, and
to provide structure to the inner liner so it does not disintegrate upon abrasive contact with pavement. This is important because the foams used have very little resistance to penetration and abrasion.
The purpose of the foam liner is to crush during an impact, thereby increasing the distance and period of time over which the helmet stops and reducing its deceleration.
To understand the action of a helmet, it is first necessary to understand the mechanism of head injury. The common perception that a helmet's purpose is to save the rider's head from splitting open is misleading. Skull fractures are usually not life threatening unless the fracture is depressed and impinges on the brain beneath and bone fractures usually heal over a relatively short period. Brain injuries are much more serious. They frequently result in death, permanent disability or personality change and, unlike bone, neurological tissue has very limited ability to recover after an injury. Therefore, the primary purpose of a helmet is to prevent traumatic brain injury while skull and face injuries are a significant secondary concern.
The most common type of head injury in motorcycle accidents is closed head injury, meaning injury in which the skull is not broken as distinct from an open head injury like a bullet wound. Closed head injury results from violent acceleration of the head which causes the brain to move around inside the skull. During an impact to the front of the head, the brain lurches forwards inside the skull, squeezing the tissue near the impact site and stretching the tissue on the opposite side of the head. Then the brain rebounds in the opposite direction, stretching the tissue near the impact site and squeezing the tissue on the other side of the head. Blood vessels linking the brain to the inside of the skull may also break during this process, causing dangerous bleeding.
Another hazard, susceptibility of the brain to shearing forces, plays a role primarily in injuries which involve rapid and forceful movements of the head, such as in motor vehicle accidents. In these situations rotational forces such as might occur in whiplash-type injuries are particularly important. These forces, associated with the rapid acceleration and deceleration of the head, are smallest at the point of rotation of the brain near the lower end of the brain stem and successively increase at increasing distances from this point. The resulting shearing forces cause different levels in the brain to move relative to one another. This movement produces stretching and tearing of axons (diffuse axonal injury) and the insulating myelin sheath, injuries which are the major cause of loss of consciousness in a head trauma. Small blood vessels are also damaged causing bleeding (petechial hemorrhages) deep within the brain.
It is important that the liner in a motorcycle helmet is soft and thick so the head decelerates at a gentle rate as it sinks into it. Unfortunately, there is a limit to how thick the helmet can be for the simple reason that the helmet quickly becomes impractical if the liner is more than 1–2 inches (2.5–5 cm) thick. This implies a limit to how soft the liner can be. If the liner is too soft, the head will crush it completely upon impact without coming to a stop. The liner is a hard plastic shell and beyond that is whatever the helmet is hitting, which is usually an unyielding surface, like concrete pavement. Consequently, the head cannot move any further, so after crushing the liner it comes suddenly to an abrupt stop, causing high accelerations that injure the brain.
Therefore, an ideal helmet liner is stiff enough to decelerate the impacting head to an abrupt stop in a smooth uniform manner just before it completely crushes the liner and no stiffer. The required stiffness depends on the impact speed of the head, which is unknown at the time of manufacture of the helmet. The result is that the manufacturer must choose a likely speed of impact and optimize the helmet for that impact speed. If the helmet is in a real impact that is slower than the one for which it was designed, it will still help but the head will be decelerated a little more violently than was actually necessary given the available space between the inside and outside of the helmet, although that deceleration will still be much less than what is would have been in the absence of the helmet. If the impact is faster than the one the helmet was designed for, the head will completely crush the liner and slow down but not stop in the process. When the crush space of the liner runs out, the head will stop suddenly which is not ideal. However, in the absence of the helmet, the head would have been brought to a sudden stop from a higher speed causing more injury. Still, a helmet with a stiffer foam that stopped the head before the liner crush space ran out would have done a better job. So helmets help most in impacts at the speeds they were designed for, and continue to help but not as much in impacts that are at different speeds. In practice, motorcycle helmet manufacturers choose the impact speed they will design for based on the speed used in standard helmet tests. Most standard helmet tests use speeds between 4 and 7 m/s (9 and 16 mph).
Standards testing
Most motorcycle helmet standards use impacts at speeds between 4–7 m/s (9–16 mph) At first glance, this is confusing given that motorcyclists frequently ride at speeds higher than 20 m/s (45 mph). This confusion is relieved by understanding that the perpendicular impact speed of the helmet is usually not the same as the road speed of the motor cycle and that the severity of the impact is determined not only by the speed of the head but also by the nature of the surface it hits. For example, the surface of the road is almost parallel to the direction the motorcyclist moves in so only a small component of his velocity is directed perpendicular to the road while he is riding. Of course, other surfaces are perpendicular to the motorcyclist's velocity, such as trees, walls and the sides of other vehicles. The other vital factor in determining the severity of an impact is the nature of the surface struck. The sheet metal wall of a car door may bend inwards to a depth of 7.5–10 cm (3–4 inch) during a helmeted head impact, meaning that it generates more stopping distance for the rider's head than the helmet itself. So a perpendicular impact against a flat steel anvil at 5 m/s (11 mph) might be about as severe as a 30 m/s (67 mph) oblique impact against a concrete surface or a 30 m/s perpendicular impact against a sheet metal car door or windscreen. Overall, there is a very wide range of severity in the impacts that could conceivably happen in a motorcycle impact. Some of these are more severe than the impacts used in the standard tests and some are less so.
The speeds are chosen based on modern knowledge of the human tolerance for head impact, which is by no means complete. It is possible to deduce how well the 'perfect' helmet outlined in the Function section of this page would perform in an impact of a given severity. If currently available data suggest that the rider is unlikely to survive in such an impact, regardless of how well his helmet performs, then there is little point in demanding that helmets be optimized for this impact. On the other hand, if an impact is so mild that the rider is unlikely to be injured at all so long as he is wearing a helmet than that impact is not a demanding test. Modern standards setters choose the severity of the standard test impact to be somewhere between these two extremes, so that manufacturers are doing their best to protect the riders who can be helped by their helmet during a head impact.
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