Motorcyclists are vulnerable to head injuries. A helmet cannot guarantee protection in all crash scenarios. Often in motorcycle cases, the issue of helmet use arises as to whether the helmet was used properly, whether the helmet was defective or whether would have prevented the injury and its effect on comparative negligence are issues of a motorcycle crash case. The science of helmets is complex area. This article cannot fully cover all aspects of helmets but, here are ten things you should be aware of in handling motorcycle cases. Different types of motorcycle helmets offer different levels of protection for certain injuries and not for other types of injuries. There are other variables as discussed below.


  1. In the United States, there are two recognized standards. They are the DOT certification and Snell Foundation certification standards for motorcycle helmets in the United States. Each motorcycle helmet has a sticker on the outside or inside, if it is a DOT or Snell Foundation certified helmet. The date of manufacture and the age of the helmet will always be shown and can be important. But as per the discussion below, just because there is a DOT sticker on the helmet does not necessarily mean it is safe to use by a motorcycle rider. Be aware there are also “novelty helmets” that are neither DOT nor Snell Foundation approved and are not legal for street use. Louisiana, La. R.S. 32:190 require that a motorcycle helmet “shall meet such other specifications as shall be established by the commissioner”. DOT sets minimum standards that all helmets sold for motorcycling on public streets must meet. The standard is Federal Motor Vehicle Safety Standard 218 (FMVSS 218) and is known as the DOT helmet standard. The Snell Memorial Foundation is a private not-for-profit organization that sets voluntary standards for motorcycle helmets, bicycle helmets and auto racing helmets, as well as other kinds of protective headgear. Snell Standards are the world’s toughest.[i] Some DOT only approved helmets can be bought at PepBoys such as the Chinese made MHR GTX full coverage helmet for $38.00 and is DOT but not Snell approved. Other higher end helmets like Shoei and Arai cost over $800 or more and are made of hand laid fiberglass and composite materials in layers to offer more protection. Most race professional agree the higher end helmets offer greater protection and last longer even though they all meet DOT standards.
  2. It is important to realize that helmet testing does not seek to precisely reproduce real life situations, rather it attempts to define a set of requirements that is analogous to the types of situations that might be encountered while engaged in a prescribed activity. Look at this video from the Snell Foundation as to how helmets are tested at You can see the test is very limited and does not test for all or even common conditions the head will experience in a crash. Snell Foundation does several tests that include the impact test, positional stability (roll-off) test, dynamic retention test, chin bar test, Snell penetration test, face shield penetration test, and flame resistance test.[ii]Even Snell Foundation helmet testing does not include responses of the neck or body as they react with the head during a crash. It is strictly a measurement of how a helmet reacts during an event.[iii] As discussed below, a helmet will not protect a rider from certain brain injuries even though it meets DOT or Snell Foundation standards.
  3. Certification using actual helmets is not done by DOT but is done by Snell Foundation. While a DOT certified helmet might have a DOT sticker on it, that helmet was never actually tested by the DOT. DOT trusts the manufacturer in China or wherever it may be. The manufacturer merely certifies to DOT that it has tested the helmet and it passed the DOT test criteria federal standards. The Snell Foundation does things different and actually tests helmets in the market itself and has one of the few certified helmet-testing labs to do so. Snell Foundation does test actual helmets submitted by the manufacturer, unlike DOT. Then Snell Foundation goes further and pulls helmets off retail shelves to make sure the quality control is there for consumers to insure the Snell certified helmets pass the more rigorous Snell Foundation Standards. There have been some articles about helmets not in fact passing DOT tests yet certified that they do pass DOT tests. Snell Foundation has found problems with helmets later Snell Foundation tests of some helmets have led to the conclusion that model was, indeed, non compliant. Therefore, the Foundation imposed corrective action upon the manufacturer according to the terms of the Licensing Agreement.[iv]
  1. A DOT approved helmet is not tested to the same standards as a Snell Foundation approved helmet. There is a good argument to be made that the Snell Foundation Standards are far stricter than DOT standards. A comparison of the two shows the Snell standards are more comprehensive. Snell Foundation does checks for helmets actually in the market pulling them off shelves and testing them. Snell uses certified machines. The Snell Standards are tougher than DOT standards. Snell requires that helmets withstand substantially larger impacts than DOT does.[v] If you are going to hit an object like a curve with your head, the Snell helmet probably offers more protection for skull fractures. But none of the two standards will protect the rider’s brain from rotational accelerations.
  1. The age and use of a helmet is important because a motorcycle helmet is only good for a limited time, due to deterioration with age and use. Some manufacturers recommend replacing a motorcycle helmet every 5 years.[vi] Some recommend replacing a helmet every 3 years. Sunlight exposure, heat and sweat will reduce the safe use protective lifespan of a motorcycle helmet. A helmet that has been used daily in hot sun and sweat exposure will not last as long nor offer the level of protection it should to be effective. The helmet must fit tightly and the chinstrap properly secured. A loose helmet from another rider, or worn in by use that is loose, or the wrong size is purchased will not work properly.[vii] Shoei helmet manufacturer warns consumers as follows: The right size and correct fitment are of enormous importance for the safety and wearing comfort of a helmet. Customers should be aware that helmets are subjected to an aging process. For that reason, the way that a helmet is cared for makes a big difference in how long it lasts. Helmets can lose their ability to provide proper safety after a crash or due to aging, in which case they should be replaced.”
  1. Once a helmet sustains an impact, it must be replaced or inspected by the manufacturer. All helmet manufacturers and Snell Foundation warn that a helmet that sustains an impact must be replaced and is not safe to use. All helmet manufacturers will inspect a helmet sent back to them at no charge. They all recommend the helmet is never to be continued to be used after any impact. This is because even dropping a helmet on concrete may compromise the helmet by crushing the foam liner and shell layers.
  1. Present certified DOT and Snell Foundation certified helmets do not protect against rotational accelerations that are know to cause brain injury.

While motorcycle helmets offer increased levels of protection, they do not protect against acute subdural hematoma (ASDH) with is the most important cause of death in severely head injured patients. The most common type of ASDH results from tearing of veins that bridge the subdural space as they travel from the brain’s surface to the various dural sinuses.[viii] High strain-rate acceleration of the head is the cause of ASDH.[ix] In Biomechanics of Acute Subdural Hematoma, by Thomas A. Gennarelli, M.D. and Lawrence E. Thibault, Sc. D., Journal of Trauma, 198, the authors concluded that new tolerance criteria of each type of head injury should be established, rather than continued reliance upon previous held concepts of head injury based on biomechanical theories. [x] Present certified DOT and Snell Foundation certified helmets do not protect against rotational accelerations that are known to cause brain injury. One study is known as the COST-327 report, published in 2001 as collaboration between several European agencies, which investigated fatalities among helmeted motorcyclists. The report concludes, “rotational acceleration is an important cause of injury and helmet design should ensure that the potential for rotation is minimized”.[xi] A new helmet 6D is not Snell nor DOT approved but it is designed to protect the brain from rotational acceleration.[xii] Better protection is offered for rotational acceleration and concussions by the 6D helmet unlike DOT or Snell helmets, which do not offer such rotational acceleration protection.

What this means is no one can design a helmet that will protect a motorcycle rider in all conditions. If you know how the crash will occur you can design and wear the right helmet for that crash but not another type of crash. Predicting how one will crash of course is not possible. 6D helmets are an attempt to offer more protection for rotational acceleration brain injuries than Snell and DOT helmets. Ironically they would not be legal to use on the streets in Louisiana, which requires DOT approved helmets. All Snell Foundation helmets meet DOT standards. But the 6D helmet is not DOT approved. More work is being done to prevent fatal brain injuries in motorcycle accidents, as the present Snell and DOT helmets are not designed to prevent rotational acceleration brain injuries.

  1. There are different standards for different helmet uses. For example for just Snell Foundation motorcycle helmet there are several motorized motorcycle and moped standards. There is the M2010 Snell Standard for motorcycle helmets. Then there is the CMR/CMS 2007 standard for child motorsports. There are also the L-99 helmet standard moped riders. There are various DOT standards. Make sure you research the right helmet standard for the helmet and use involved.
  1. There is no research to show helmets cause neck injuries. This is a myth that has no scientific support according to NHTSA. [xiii]
  1. Noise generated by motorcycle helmets can cause premature deafness.[xiv] In the COST 327 report it was recommended that measuring noise as part of a motorcycle helmet standard be implemented. Sound levels of over 90 db were found in the COST 327 study.



Helmets offer protection in the event of certain crash scenarios but the above factors, including type of impact, type of helmet, type of certification, fitting of the helmet, age of the helmet and other factors above can vary how effective a helmet is in protecting from certain motorcycle injuries. Helmet technology is always evolving. 6D just introduced a helmet that helps prevent concussions in low speed crashes such as motocross and brain damage from angular acceleration.[xv] Team Honda riders were the first to use the new 6D helmet due to motocross riders suffering from brain injury and concussions, which DOT and Snell Helmets do not prevent. 6D plans to introduce another model for high-speed road type crashes to protect from angular acceleration type brain damage, which present helmets do not. How this will be possible with DOT and Snell standards met remains to be seen. The 6D street helmet is not available as of date.


[ii] Snell Memorial Foundation at

[iii] Snell Memorial Foundation at

[iv] Snell Memorial Foundation at



[vi] See. Shoei helmets website at



The life of a helmet depends on how it is used. A helmet should be replaced if one or more of the following points apply:

  1. There was a fall that resulted in an impact on the helmet.
  2. The helmet fits looser than when it was purchased due to frequent use.
  3. The EPS liner has come away from the helmet shell.
  4. The EPS liner shows signs of wear and is beginning to break up, or if it has been exposed to heat or a solvent and has melted.

SERVICE: SHOEI helmets are covered by a five-year, limited warranty, and SHOEI will repair or replace the helmet if it is found to suffer from flaws in materials or workmanship.

Shoei offers a free impact and safety inspection service for any SHOEI helmet.*


[viii] Biomechanics of Acute Subdural Hematoma, by Thomas A. Gennarelli, M.D. and Lawrence E. Thibault, Sc. D., Journal of Trauma, 1982, Vol. 22, No. 8.

[ix] Biomechanics of Acute Subdural Hematoma, by Thomas A. Gennarelli, M.D. and Lawrence E. Thibault, Sc. D., Journal of Trauma, 1982, Vol. 22, No. 8. Helmeted rhesus monkeys were tested with head injuries produced in a laboratory so the effects of acceleration were studied in isolation for the first time. Single acceleration-deceleration pulse to the head form 5 to 25 milliseconds.,p. 680.

[x] Biomechanics of Acute Subdural Hematoma, by Thomas A. Gennarelli, M.D. and Lawrence E. Thibault, Sc. D., Journal of Trauma, 1982, Vol. 22, No. 8., p. 685

[xi] COST 327 Motorcycle Safety Helmets, Final Report of the Action, 2010 published by the European Commission for Directorite General for Energy and Transport



[xiv] COST 327 Motorcycle Safety Helmets, Final Report of the Action, 2010 published by the European Commission for Directorite General for Energy and Transport, executive summary p. x.