This document is no longer current and only maintained for historic purposes.
Released : 25/07/2015
Updated : 26/09/2016
Version : 2.5
Prepared by: Tim Kelly
If you ride a motorcycle and consider your helmet to be an integral part of your safety equipment then I implore you to read the entire document as I believe the research I’ll highlight will demonstrate why wearing an helmet meeting the AS1698 standard may not offer you the best protection available in decreasing your risk of serious injury or fatality in the event of an accident based on the research quoted.
I would also add this document does contain medical terminology and does describe some of the types of trauma the head may experience in an accident and therefore, reader discretion is advised
Australian Standard (AS) 1698 was created in the 1974 as an amalgamation of previous helmets standards with the second edition being released in 1980, the third in 1988 and the fourth and most current version being released in 2006 as AS/NZS 1698:2006.
As such, whilst we are able to view the 1988 version of the standard, the latest version (2006) is not freely available to members of the public as the rights to these standards were sold to an international corporation and therefore, in order to access a copy of the standard there is a requirement to pay a fee in order to access the standard.
Update: It would appear that the 1698:1988 version is also controlled by SAI GLOBAL as per this watermark taken from AS 1698 (1988) (English): Protective helmets for vehicle users [Authority: Australian Government Gazette of 14/12/2007]
Criticisms of AS1698
Over the past 25 years a significant body of both national and international research has been undertaken in the field of motorcyclist accidents which have allowed researchers to highlight and determine the key characteristics a helmet design should incorporate in order to provide maximum protection to the wearer in the event of an accident.
As a result of this deeper understanding of how helmets should be constructed was formed, numerous researchers during this time have called into question the significant shortcomings of the AS1698 standard in regards to either be behind or in direct contrast to known science in the field of motorcycle helmet development research & Standards.
The key points raised by researchers have been
- The failure in AS1698 to provide any form of chin bar testing in full face helmets.
- The AS1698 requirement for helmets to pass the energy attention test and its impact on helmet liner weight and stiffness.
- The AS1698 requirement for helmets to pass the spear penetration test and its impact on helmet weight and stiffness.
Chin Bar Testing
The chin bar as the name suggests the bar which runs across the chin of a full face helmet and its primary safety purpose is to protect to the lower face and jaw from injury.
Roughly 80% of all motorcyclists wear this type of helmet.
From the 2007 report titled ‘Helmet protection against basilar skull fracture’ sponsored by the Australian Transport Safety Bureau (ATSB) by Gibson et.al.
A review of available field data on the incidence and causation of BSF to motorcyclists was completed and the findings compared with crashes collected in the CASR Head Injury Database. This database contains in-depth investigations of 174 mainly fatal motorcycle accident cases collected in South Australia between 1983 and 1994. It includes autopsy data, including an investigation of neck injury, the helmet and a detailed crash report. The CASR data was found to be representative of fatal crash studies in the literature and to consist of high severity crashes. In 70% of the cases full face helmets were worn. BSF was seen in 59% of these cases. Almost 50% of the severe impacts to the head were in the facial region and 42% of these impacts were to the chin bar. The prevalence of BSF was found to be mainly due to the migration of the skull fracture to the base of the skull due to the severity of the impact to the face (and other regions of the head)
A key finding was
The study shows that the protection offered by the Australian motorcycle helmet needs to be extended to cover the facial area, with the aim of reducing facial fractures
These results mimic a similar finding to the 1988 NSW study by Dowdell et al. as described by Whyte et. al. ‘HEAD INJURY AND EFFECTIVE MOTORCYCLE HELMETS’
A comprehensive review of the performance of Australian market motorcycle helmets in crashes was performed by Dowdell et al. in NSW, Australia. Cases were included on the basis that the crash was of sufficient severity to have the motorcyclist admitted to hospital and that the motorcyclist was wearing a helmet approved to the current Standard. 200 cases were collected, of which 72 were fatal and 128 non-fatal. More than two thirds of the impacts to the helmet in these cases were tangential. In the cases where a head or neck injury occurred, 50% of impacts were to the general frontal area of the helmet. Local skull fractures (vault fractures) were associated with impacts adjacent to the fracture site.
Gibson et.al describes the outcome
A recommendation was made that specifications be developed for a test aimed at reducing the effect of frontal impacts to the face by improving the energy absorption of helmets in this area.
In 1995, the European Commission Directorate General for Energy and Transport initiated a Cooperative Scientific and Technical Research (COST) program to investigate Motorcycle Safety Helmets across several countries including Finland, France, Germany, Hungary, Italy, The Netherlands, Switzerland and United Kingdom using a total of 253 accident cases collected over a 3 year period between 1995 and 1998 with the report being released in 1999.
A key finding from this study was
Most injuries are sustained at the front of the head, with more then two thirds of skull fractures involving chin impact (and that) a high proportion of fatalities with head injuries sustained base of the skull fractures, almost always caused by direct impact, through the chin guard, to the facial skull, and in turn through the skull base. Thus the chin guard is an area of the helmet that requires particular attention.
In 2015, Whyte et. al. (2015) using data collected by Neuroscience Research Australia as part of an in-depth case-control study of 88 non fatal motorcycle crashes in NSW found that the majority of riders (86.4%) wore a full face type motorcycle helmet which included a chin bar and the remainder wore an open face “jet” style helmet (13.6%).
Injury data showed that in 21 of the 88 cases, head injury was sustained with superficial head injuries being the most common with the face sustaining the majority (80.8%) and ‘of the 9 fractures to the head 1 (11.1%) involved the skull vault and the remaining 8 (88.9%) involved the facial bones or teeth’
Of the 88 accidents studied, ‘there was observed or reported damage to the helmet in 76 cases (86.4%), 10 helmets (11.4%) were undamaged and the condition was not known for 2 (2.2%)‘. Using this data ‘the location of the damage on 65 inspected helmets was mapped on a schematic of the helmet divided into zones based on the crown, front, sides and rear of the helmet at varying levels of elevation from the helmet rim’.
This image is shown below and it’s important to note that it only shows helmet helmet damage assessed. Impacts attributed to the visor and chin bar zones cannot be displayed for 11 open face helmets (of these, 5 without a visor) as there is no structure available to assess damage.
The outcome of this body of work which 27 years ago first highlighted the need for a chin bar test, was summarised by Whtye et.al. as follows
…in the distribution of impacts shown… a high frequency of impacts occurred to the front and facial area of the helmets of crashed riders. This is in agreement with previous major crash investigation studies in Europe , the US  and Australia [21,22]. Despite this, the chin and facial region is outside the require region of protective coverage required by many motorcycle helmet standards, including the Australian Standard AS 1698.
Opposed to this, the ECE developed chin bar test derived on the research from the COST 327 project has since been adopted in the FIA 8860-2004 Advanced Helmet Test Specification, which is designed for use in Formula 1 motor racing along with being part of the ECE 22.05 helmet standard. A standard used in over 50 countries worldwide including New Zealand, Germany and the UK as well as 1 of only 3 allowed standards in the ultimate test of motorcycling equipment safety, MotoGP.
Energy Attenuation Test
From the 2001 report ‘Improved Shock Absorbing Liner for Helmets’ sponsored by the ATSB Morgan et. al.
For helmets to be certified to the Australian/NZ Standards, they must satisfy the requirements of two performance tests (a) the energy attenuation test and (b) the penetration test. Both tests require the use of a solid magnesium headform that endeavours to simulate the human cranium. The only resemblance is the shape. The helmet is attached to the headform and dropped from standard heights onto either a flat or hemispherical steel anvil.
The report described the testing methodology and the implications on helmet liner foam choice
It should be noted that the magnesium headform used in testing is more rigid than the human skull and is more capable of producing a crushing effect on the helmet liner. Researchers (Corner et.al., 1987; Mills and Gilchrist, 1991) have demonstrated that this rigid headform should be replaced with one that can more reasonably simulate the human cranium, e.g. the Wayne State University Hodgson Headform. The magnesium headform produces more severe damage to the helmet liner than would be the case for a real head in a similar impact (Corner et. al., 1987). To satisfy the requirements of the Australian/NZ attenuation test (incorporating the magnesium headform) manufacturers and designers have had to provide a relatively stiff polystyrene-foam liner with high densities, from 70 to 90 kg/m3. Due to the stiffness of the liner, the human head deforms elastically on impact, causing cranium distress. A distortion of 1-2 mm of the skull is the threshold of intracranial damage (Viano, 1985).
The report found
The stiffness and hardness of helmet liners are directly related to the stringent performance requirements of the Australian/New Zealand Standard’s impact attenuation test (AS1698 and AS/NZS2063).
The authors also highlighted (with bold text in the document)
Irrespective of the type of headform used in trials, researchers have concluded that helmet liners should be less stiff and ideally be made of lower density foam to absorb impact forces rather than transfer the forces to the cranium vault.
Again, from the same report and as quoted from Gilchrist et. al. (1994)
The second impact test required by some standards prevents the optimisation of the liner foam density for the first impact and leads to higher yield stress and stiffer foams. They have explained that the major impact damages about 100mm area of the helmet which it is about 5% of the whole protecting area of the helmet. It was concluded that the second impact test is unnecessary and possibly detrimental
Spear Penetration Test
The Australian Standard requires motorcycle helmets to withstand a penetration test which Morgan et. al. briefly describes below
A steel conical striker with a mass of 3kg is dropped from 3m onto a helmet fitted headform. The helmet will only pass this test if the point of the penetrator does not make contact with the magnesium headform…Only the crown of the helmet is tested.
In the 4 year review ‘Comparison of safety helmet testing standards’ undertaken between 2006-2010 on behalf of the Department of Aeronautics, Imperial College London, authors Ghajari et. al stated that the in regards to penetrating testing
The penetration test is not prescribed in the European Standards, since statistical analysis has shown that impact with penetrating objects are very unlikely (COST 327)
This finding was also determined to be an agreement with earlier research performed by Gilchrist et. al. (1994 a, 1996) that found
the thickness of the helmet shell is largely determined by the penetration test which is felt as irrelevant since it corresponds to a very rare phenomenon in real accidents.
Further to this, the research also concluded
Penetration tests lead to thick composite helmet shells that behave in a very stiff way when striking rigid flat surfaces and as a consequence stiff shells designed to pass penetration tests provide a worse protection than more flexible shells in the much more common cases of impacts with flat or curved surfaces
In regards to crash configurations between Australian and European motorcyclists, the results are shown below using the COST 327 classification and include results from COST 327, MAIDS, CASR and NSW datasets (when the cause was known). The reader should also note the COST 327 study focused specifically on head injuries in motorcyclists and CASR dataset prominently contained fatalities (94%) and therefore these datasets maybe bias towards object orientated collisions whilst the NSW dataset contained no fatalities.
COST 327: n = 218, Avg Speed 55kph, 38% fatality rate
MAIDS: n = 921, Avg Speed 53.6kph, 11.1% fatality rate
NSW: n = 88, Avg Speed 52.3kph, no fatalities included in dataset
CASR: n = 174, Avg Speed 80kph, 94% fatality rate
Why Helmet Weight Matters
In the 2007 report produced by Gibson et. al. sponsored by the ATSB the authors noted that
A correlation has been demonstrated between BSF and helmet weight (when >1.6kg) (Konrad et al. 1996).
Unfortunately, this summerised key point may be considered misleading and as such the actual conclusion of the study by Konrad et al. was that ‘helmets weighing more than 1,500 grams increase the risk of a basal skull fracture‘ and this was clarified later in the report which also stated the following in regards to helmet weight
Konrad et al. (1996) retrospectively studied 122 fatally injured motorcyclists. The overall incidence of BSF was 9.2%. There was a positive correlation between the incidence of complete or partial ring fractures of the base of the skull and the weight of the involved helmet. There was a significant increase (p = 0.012) in incidences of this type of fracture when the helmet weighed more than 1,500 grams. Five helmets in the study weighed more than 1,600 grams; in this subgroup, only one patient’s skull base was intact.
* n = 122. Statistical tests were performed using ANOVA, Fisher’s exact test, Student’s t test, and the chi 2 test. A p < 0.05 was considered significant
The authors also added
Some researchers have found that in specific circumstances, full-face helmets may promote injuries. Reported helmet associated injuries include disruption of the head and neck junction where no signs of impact against the head could be detected (Krantz 1985). Further, BSF due to inertia loading of the skull base by the head and helmet was reported by Konrad et al. (1996). In both of these injury types, the mass of the involved helmet appears to have significance.
The other way to consider the how helmet weight affects your safety is to consider an accident at 100kph where your body comes to a complete stop in .3 of a second wearing a 1.6kg helmet. This is a deceleration figure of 333.28kph with G force applied to the body of around 9.47g’s. With some quick maths we can see that at 9.4 x 1.6kg, your helmet now weighs 15kg and it’s your neck that needs to stop that weight from wanting to continue moving forward at 100kph on initial impact.
Causes of Basal Skull Fracture (BSF)
Gibson et al 2007 stated that
Basilar skull fractures have been attributed to various mechanisms including impacts to the mandible or face and the cranial vault, or due to inertial loading by the head (often called whiplash type injury). Such inertial loading occurs, for example, when the chest of the motorcycle rider comes to a sudden stop on contact with an object such as a vehicle or guard rail. The head is then slowed by loading of the neck. Ring fractures may also result from vertically directed contact forces applied either inferiorly to the crown (compressive forces) or from superiorly directed forces applied to the occiput or the mandible.
But to put it simply, impacts to the face, particular the chin or any other incident that causes the neck to become the primary object for deceleration of the head will result in a BSF injury. So for instance, if your helmet shell is too stiff and the liner too stiff, it will be the necks responsibility for absorbing the brunt of the impact… or if you helmet is too heavy, the helmet weight will contribute towards pushing you head forward under extreme deceleration.
The other common form of BSF according to research is from impacts to the chin bar, which then transfer the force through the helmet shell, into the helmet liner and then onto the chin.
AS1698 Helmet Weights
http://www.crash.org.au/ is an Australian based Consumer Rating and Assessment of Safety Helmets (CRASH) program run by a consortium of government agencies and a motorist organisation which share a common interest in improving motorcycle safety. The program is funded by Transport for New South Wales, NRMA Motoring & Services, and the Transport Accident Commission (TAC).’
The CRASH data provides a number of key safety and ergonomic metrics on their site in relation to an individual helmet meeting the AS1698 standard with a total of 89 Full Face, Flip Up, Dual Sport, Motocross and Open Faced Helmets reviewed at the time of access. Of interest to this document is the helmet weight metric which is based on the average weight of (usually) 3 Large helmets.
Using this data in conjunction with the weight limit research by Konrad et al. 1996 which found that helmets greater then 1500g (1.5kg) increase the risk of BSF I was able to isolate all helmets exceeding this weight threshold and from that we find that a staggering 66% of helmets reviewed on the site exceed this recommended threshold and as such, only 34% being deemed light enough not the contribute towards a BSF injury.
However, this initial figure is somewhat skewed in that if we then isolate the data set to full face helmets only which are the most common types of helmets used in Australia as previously noted, we find that 85% of all helmets currently tested and available on the CRASH website exceed the recommended weight threshold and therefore, only 15% of helmets are below a known scientifically verified safe weight limit… or roughly, 8 and out every 9 helmets tested on the CRASH website having received AS1698 accreditation have a total weight which as per the research suggests, will contribute towards a rider sustaining a BSF injury in the event of an accident.
ECE 22.05 Helmet Weights
http://sharp.direct.gov.uk/ SHARP is the safety rating for motorcycle helmets set up by the British Department for Transport in November 2007 and provides an independent assessment of how much protection a helmet can offer in an impact.
The Sharp data provides a number of key safety and feature metrics on their site in relation to an individual helmet meeting the AS1698 standard with a total of 310 Full Face and System helmets reviewed at the time of access . Of interest to this document is the helmet weight metric which is based on the average weight of large helmets.
Using this data in conjunction with the weight limit research by Konrad et al. 1996 which found that helmets greater then 1500g (1.5kg) increase the risk of BSF I was able to isolate all helmets exceeding this weight threshold and from that we find that only 4 out of every 10 helmets reviewed on the site exceed this recommended threshold in comparison to the AS1698 standard.
AS1698 Helmet Weights vs ECE 22.05 Helmet Weights
Using the data available from the CRASH and SHARP websites, there were a total of 21 suitably matched helmets available for weight data comparison between the AS1698 Standard and the ECE 22.05 standard. This data is shown below with the red area showing helmets over the BSF weight threshold limit.
As such, from the graph above we can see that in roughly 75% of the helmets compared, the AS1698 version was required to be made heavier for the standard then its ECE counterpart and on average this was 123 grams.
Further to this, the data demonstrated for 48% of all ECE versions of the helmets that were below the BSF threshold when certified for ECE 22.05, the need for a thicker shell and stiffer helmet liner of the AS1698 standard now placed them above the BSF threshold.
In summation, the research presented in this document has clearly demonstrated
- a correlation between helmet shell weight and stiffness and BSF injuries
- helmet liner stiffness and head injury
- the critical importance that chin bar testing has in relation to BSF injuries
This document is also the first (I believe) to actually perform a weight comparison against the AS1698 standard in relation to BSF injuries using the weight threshold limit and as such, given the unacceptably high ratio of helmets that exceed this limit as a result of having to have a thicker shell and stiffer helmet liner in order to gain AS1698 accreditation, motorcyclists should be now be asking themselves if they still want to be wearing a helmet that uses a standard that is in direct opposition of all known science in regards to the safest helmet design possible.
Morgan, D.E. and L.S. Szabo. ‘Improved Shock Absorbing Liner For Helmets’. Web. 18 July 2015.
Ghajari, M., Caserta G.D. And Galvanetto U. ‘Comparison of safety helmet testing standards’. Web. 18 July 2015.
Gibson T.J. and Thai K. ‘Helmet protection against basilar skull fracture’. Web. 18 July 2015.
Helmet protection against basilar skull fracture Web. 18 July 2015.
Konrad C.J., Fieber T.S., Schuepfer G.K. and Gerber H.R. 1996. Are Fractures of the Base of the Skull Influenced by the Mass of the Protective Helmet? A Retrospective Study in Fatally Injured Motorcyclists – The Journal of Trauma: Injury, Infection, and Critical Care Issue: Volume 41(5), November 1996
Whyte T., Gibson T., Brown J., Milthorpe B. and Eager D. ‘Mechanisms of head and neck injuries sustained by helmeted motorcyclists in NSW, Australia.’
COST 327 Web. 18 July 2015.
Whyte T, Gibson T, Milthorpe B and Stanford G. Web. 29 July 2015.
CRASH Web. 18 July 2015.
SHARP Web. 18 July 2015.