Observations on Impact Attenuation Criteria for Playground Surfaces by Professor David Ball

I reprint in full an important and helpful paper by David Ball, Professor of Risk Management at the Centre for Decision Analysis and Risk Management. The paper, ‘Observations on Impact Attenuation Criteria for Playground Surfaces, discusses some of the questions and tensions that inevitably arise whenever risk management decisions need to be made.

The paper – prompted by the American Society for Testing and Materials’ (ASTM) proposal to revise downwards the Head Impact Criterion for playground impact absorbing surfacing – is of wide relevance in that it sets out a way of thinking about risk in the context of wider social policy goals. I urge anyone involved in making decisions about children and teenagers’ play and learning to read the succinct and clear paper that follows.

The paper has been sent to ASTM.

Centre for Decision Analysis and Risk Management


David J. Ball, Professor of Risk Management, 

Centre for Decision Analysis and Risk Management


1.  This note is prompted by a proposition, originating from the ASTM in the USA but which was also considered by CEN in Europe in 2014, to revise the Head Impact Criterion (HIC) for playground impact absorbing surfacing (IAS) downwards from 1,000 to 700. The stated aim is primarily to reduce the risk of brain injury from headfirst falls to the ground, though some also refer to a reduced risk of long bone fractures as another benefit.

2.  Although on the face of it the proposition sounds entirely rational it is a cause of controversy. On the one hand, in support of the proposition, there is evidence from road traffic accidents and other non-play environments that children may sustain brain injury at a HIC of 1,000 or less. For some this immediately implies that action is needed in all settings where children are potentially at risk of head injury. On the other hand, there is concern that an intervention of this nature might have significant and unintended consequences for play provision with knock-on implications for overall child welfare because play is an essential constituent of growing up.

3.  Both concerns are legitimate. It can be assumed that all parties want the best for children, but it has not been agreed how this is to be achieved. This discord might be attributable to deficiencies in communication between the parties involved. The situation does indeed appear to resemble a classic stand-off between parties who seek the same ultimate goal – the welfare of children and young people – but approach it from different perspectives.

4.  It may be worth pointing out that such situations are relatively common in risk management decision making. For example, Professor John D. Graham, Dean of Indiana University School of Public and Environmental Affairs, wrote a book about it citing numerous examples.[1] The problem is that any one intervention, be it to promote safety from injury, improve health, protect the environment et cetera, may adversely affect the achievement of different goals important to other people.

5.  In the context of the present example of IAS, it is likely that one element of the controversy revolves around the pursuit of lower head injury rates versus the quest by others for improved physical and emotional health through greater uptake of what they regard as enhanced play opportunities. Some would argue that these two things can be pursued independently, but others see them as connected such that actions to promote one affect the other. The late Howard Margolis, Professor of Public Policy Studies at the University of Chicago, explained such clashes as coming about because some participants in a debate see their quest from an absolutist perspective, that is, ‘Nothing can be more important than this,’ whereas others believe that all decisions involve tradeoffs and compromises.[2]

Approaches to public policy decision making 

6.  It is relevant to be aware that attitudes to public policy decision making have changed markedly over the last half century. In the 1950s there was a tendency to believe that decisions about public policy were best left to technical experts. This is no longer seen as valid nor acceptable in policy making circles, on either side of the Atlantic. The position now, in N. America and Europe, is that decisions that have significant impacts on society should encompass all stakeholder views and be sensitive to the variety of concerns and needs. While it is entirely appropriate that the best technical evidence should be used to inform policy decisions, those decisions should not be driven by purely technical inputs. For example, who would want a hospital to provide patient care with only technical input being permitted in the determination of patient health choices? This shift in thinking is set out by the US National Research Council in its influential book ‘Understanding risk – Informing decisions in a democratic society.’ In Europe, one finds equivalent messages in the publications of the Lausanne-based International Risk Governance Council, and in policy documents by individual Member States.

7.  This change in approach to decision making has been recognised and adopted within international Standards such as ISO 31000 (2009) which states that risk management: takes human and cultural factors into account; recognizes the capabilities, perceptions and intentions of external and internal people; is transparent and inclusive; incorporates appropriate and timely involvement of stakeholders and, in particular, decision makers at all levels of the organization, ensuring that risk management remains relevant and up-to-date; involvement also allows stakeholders to be properly represented and to have their views taken into account in determining risk criteria.

The importance of play and changing understandings of what constitutes optimal play

8.  Promoting physical activity is now seen by many health exponents and policy makers as not only important but even as “the best buy in public health.”[3] Achieving this within a population means starting at an early age and one of the best opportunities is through appropriate play provision. Play providers and some researchers additionally recognise the emotional and social necessity of play for developing children and young people. Play is not just about having fun and nice times, though that is obviously important, but also about behavioural experimentation and the asking of sometimes scary questions. Coupled together, these understandings emphasise the need for far more forthright policies on the provision of appropriate play opportunities.

9.  A second important shift is the recognition that an essential ingredient of play is actual provision of exposure to risk and challenge.[4] After several decades of what has occasionally been described as the ‘dumbing down’ of play opportunities, the underlying quest has changed from one of the pursuance of lower injury rates to one of how, in the wider public health interest, to optimise the balance between risk exposure and safety.

10.  Other factors include the recognition that children of all ages, including older teenagers, need play opportunities i.e. it is divisive to think of play as an activity solely for toddlers or, say, under-twelves. One implication of the latter is that more challenging circumstances are warranted in some situations, and possibly less in others. One size does not fit all. A further shift in thinking which may be observed involves the growing recognition of the importance of exposure to nature.[5] In time, this too is likely to impact on thinking about optimal play provision.[6]

11.  Taken together, these developments point to a changing landscape of play provision which is only gradually beginning to take place, together with an enhanced requirement for carefully crafted policy making if these important opportunities are to be realised.

12.  In para. 5 it was noted that policy decisions may be approached from different perspectives. The example given was of a single-minded approach focused upon one objective (injury prevention in that case), and the other of trying to optimise amongst a number of sometimes competing objectives. From a public policy perspective the latter approach is invariably the correct one. This is because the aim is to maximise the total good, even if this means tolerating some risk. This is the way public policy decision makers would approach the evaluation of any significant policy intervention. It would not be sufficient, for example, and to use a medical analogy, to automatically sanction the use of a drug X on a National Health Service even if research showed it to reduce the risk of, say, cancer by 90% without first asking a number of important questions. These would include, ‘What is the baseline risk of the type of cancer under consideration?’ (if it is small, then even a 90% reduction becomes less imposing) and ‘What are the other implications of adopting this treatment?’ For example, some drugs are enormously expensive and would drain resources from other programs, and some have serious side effects.

Technical arguments and counter-arguments 

13.  In the case of IAS, basic information on its performance has been available for decades and much of what is now being said in support of a revised HIC value is not new although it may not have been common knowledge simply because most people do not have time to read academic tracts or perhaps are disconcerted by the research jargon. For example, in a 1989 publication on playground safety[7] which was widely disseminated in the UK and to some extent abroad, it was reported that a HIC of 1,000 in no way guaranteed a safe playground should you fall on your head. According to the scientific evidence the percentage of the population expected to experience severe brain injury at a HIC of 1,000 was given as 15% (confidence interval of 3-35%) based on the then research.[8] Even at a reduced HIC of 500 the risk of serious brain injury was still present. It has thus been no secret all along that IAS Standards writers had knowingly accept a certain level of risk and, if you believe the percentages, quite a high level. However, the fact has always been that serious head injuries of this kind were exceedingly rare on playgrounds, so the choice of a HIC with a high associated risk would not have had an observable consequence in terms of a statistically significant increase in TBIs (traumatic brain injuries) or fatalities[9] and this may be why it was considered reasonable to select a HIC value which forecast a 15% rate of severe brain injury. Otherwise, it would have been totally unacceptable.

14.  In an ASTM document dated 18 November 2013 (WK44118)[10] is an account of the new ASTM rationale for reducing HIC. It has to be said that this document as written lacks clarity from the perspective of an outsider. It seemingly conflates the science behind the relationship between HIC values and the risk of TBI with the value-based policy decision about what level of risk is tolerable. This suggests the author may be unfamiliar with the US approach to risk-related decision making as described above (para. 6) which separates these functions. The two are quite different things and the issue is not to do with scientific accuracy, as is also inferred, but about the tolerability of a risk. A second issue is that the risk of a TBI is not dependent upon the impact attenuating properties of the surface alone, but upon that in conjunction with a host of other factors which are not mentioned in the ASTM memorandum. For example, how many children get into that situation in the first place? The answer to the latter question must be very, very few. This has been demonstrated by detailed studies of playground accident statistics.[11]

15.  Unfortunately, the acceptance of a 15% risk factor for TBIs (and a higher factor for lesser injuries) did not prevent the use of the epithet ‘safe’ as in ‘safe playground’ in connection with playgrounds fitted with IAS. The consequence has been a popular notion that playgrounds can be made risk-free. Such notions, wherever encountered, are known to be dangerous because they can instil a lower level of care amongst those exposed, in this case parents, guardians and children themselves, who believe they have been assured of their safety whatever they do or neglect to do. From an educational and safety perspective this is the antithesis of what is needed, for behaviour is a major determinant of risk.

16.  Some research published in 2007 has found that during the period when IAS were being installed (1988-2002) the main discernible trend in injuries was not in fact a decrease in injuries, but an increase in the number of lower arm injuries on playgrounds.[12] Although not conclusive on its own, it is consistent with a behavioural change predicated upon false beliefs about safety. IAS were of course not designed to reduce the risk of limb injuries, although research has found that they do have some positive effect (in the absence of behaviour change) in this regard.[13] Evidence from both Europe and N. America shows that even young children are aware of hazards and respond to changes in the environment which may amount to compensatory behaviour. Thus, seeking to bring about safety by purely engineering adaptations has the potential to fail, which may be why playground injury numbers have remained relatively constant even while all of these safety interventions have been made.

17.  Perhaps more important, the target risk which is addressed by IAS is that of life threatening brain injuries attributable to falls from height onto the forehead in playgrounds. As mentioned in para. 13, even before the advent of IAS there were very few such cases and consequently the prior risk, as it can be called, of this type of event was very small. This raises questions about the utility of IAS from a public policy perspective. If the prior risk is very small there is far less to be gained from adopting the measure than if that risk were high. Coupled with the high cost of IAS, the issue of its practicability as a universal requirement is thus called into serious question.[14]

Concluding remarks

18.  It is not easy to argue against any measure which purports to increase safety from injury, especially so when children are involved. The facts are, however, that there are many desirable goals and there is always competition for resources. In this situation, the appropriate path is to seek to maximise overall benefit and in this context of play one must think about health and developmental opportunities as well as safety from injury.

19.  As research and experience have progressed, so have the times changed and the significance for children and young person’s health of having regular exercise, experiencing and learning to cope with real risk, and encountering natural surroundings, has gained in prominence on the policy agenda. This has major implications for the approach to play provision and although safety from injury will rightly continue to be an important issue it is eclipsed by matters related more to health and wellbeing in the round.

20.  Given the lack of direct evidence that a change in HIC would lead to a tangible public health gain, or one which is in any way commensurate with the cost and other implications of such a policy, it is questionable that this route should be taken. Essentially the pursuance of a lower HIC is a conservative strategy which is founded in existing ideologies about the objectives of play, whereas the paradigm which now challenges it seeks to bring about a greater benefit by shifting and broadening the focus.

DARM   16 March 2015

[1] J D Graham and J Wiener, ‘Risk versus risk – tradeoffs in protecting health and environment,’ Harvard University Press, 1985.

[2] H Margolis, ‘Dealing with risk – why the public and experts disagree on environmental issues,’ University of Chicago Press,1996.

[3] e.g. http://www.ukactive.com/downloads/managed/Dr_David_Walker_Deputy_Chief_Medical_Officer_ukactive_Summit.pdf

[4] Play Safety Forum, ‘Managing risk in play provision – position statement,’ 2004 & 2013.

[5] e.g. Richard Louv’s ‘The last child in the woods.’

[6] Something of this tendency may be observed in ‘Design for play,’ published by the National Children’s Bureau, 2008.

[7] K L King and D J Ball, ‘A holistic approach to accident and injury prevention in children’s playgrounds,’ London Scientific Services, 1989. See, in particular, Figure 7 p104.

[8] Essentially the same figure of 15% is reported in the 2011 BSI publication ‘Head and neck impact, burn and noise injury criteria – A guide for CEN helmet standards committees.’

[9] The underlying rate of fatalities from falls on US public playgrounds is about 1 per annum according to the CDC (http://www.cdc.gov/homeandrecreationalsafety/playground-injuries/playgroundinjuries-factsheet.htm). In the UK the underlying rate is about 1 fatality per three or four years from all playground causes.

[10] http://www.astm.org/DATABASE.CART/WORKITEMS/WK44118.htm

[11] A UK reference is: http://www.hse.gov.uk/research/crr_pdf/2002/crr02426.pdf

[12] D J Ball, ‘Trends in fall injuries associated with children’s outdoor climbing frames,’ International J Injury Control and Safety Promotion, 14(1): 49-53, 2007.

[13] D J Chalmers et al., ‘Height and surfacing as risk factors for injury in falls from playground equipment,’ Injury Prevention, 2: 98-104, 1996.

[14] D J Ball, ‘Policy issues and risk-benefit trade-offs of ‘safer surfacing’ for children’s playgrounds,’ Accident Analysis & Prevention, 35(4), 417-424, 2004.


7 responses to “Observations on Impact Attenuation Criteria for Playground Surfaces by Professor David Ball

  1. Pingback: Can we go too far when it comes to children’s injury prevention? | BCIRPU

  2. It would appear that replies to items 2-6 of Prof. Ball’s paper did not get to the post. Therefore they appear here.

    Reply 2; There is a world of safety systems based on simulations as we hesitate to put real humans at risk of death in a real study. Try to get that one past a university ethics committee. So what been done in the past is; Col. John Stapp voluntarily strapped himself into a rocket sled and was sent off at high accelerations until he experienced 40 g’s and broke ribs, and experienced temporary blindness, it was decided that Col. Stapp needed to live so he is replaced in the rocket sled by a pig and they die at a sustained 80 g or 125 g depending whether they are forward or backward facing, we then subject non-human primates outfitted with accelerometers to their heads and have metal slammed into their heads to see what kills them, for the naysayers on the non-human primates, we take cadaver heads, fit them with accelerometers and drop them on a steal anvil to see what will kill them again, or we question what it takes to scramble brains and sit non-human primates in a fixed position and cause their heads to move quickly to see if brain damage occurs without any sign of damage to the skull or scalp. None of these have anything to do directly with automotive or the playground, but the ability of the human body to withstand linear or rotation acceleration. This did result in the automotive industry developing first the WSTC, the SI and then HIC, which we are discussing today. This did get adopted by the automotive industry, the helmet industry, the turf industry and yes playgrounds to measure impacts that are injurious at various magnitudes. The Abbreviate Injury Scale (AIS) that has been adopted in assessing magnitude of injury around the world become the descriptor. Mixing the removal of hazards with the “unintended consequences” and the benefits of play provision does not even begin to make sense.

    Reply 3; This may well be; however it assumes that the people wanting to remove hazards from playground and prevent a 16% risk of death and a 10% risk of skull fracture are anti-play or anti-accessibility. That could not be further from the truth. These are people who believe in play and volunteer their time and funds forms of advancing play such as; the US Play Coalition, ASTM and other play opportunities through work with the US Access-Board and the National Center on Accessibility. The welfare of children is based on the provision of good play challenge that is age appropriate and does not expose them to hazards beyond the injury thresholds stated in various standards.

    Reply 4; Playground surfacing is a passive system that should only be active when required, the child landing on it. The protective surfacing has very little to do with play value other than when it is on a hill or rumble strips for wheelchairs users outside the use zone. The surface is just there to give the falling child something to land on. There are some people, believing in the play value of sand, suggest children should play in the sand wherever they want – not true. The USE ZONE is meant for children to fall into and there is a situation in Canada where child played with a toy in the sand within the use zone and another child, not knowing there was an obstacle in the use zone, jumped over the railing and landed on the child breaking the bottom child’s leg in a number of places requiring surgery, pins and a few years of rehabilitation.

    Reply 5; Surfacing standards have been in place since the early 1980s with the publishing of the CPSC Handbook. The evolved into ASTM, CSA and CEN standards that have used the same HIC and Gmax values since the early 1990s and have not reduced injuries by their efforts, but rather the number, severity and costs are going up. Obviously the old values are not working and it is time to re-evaluate the prevention by lowering the impact values. Putting the removal of hazards vs play value and challenge as being mutually exclusive is not logical as the innovation in play structure and play environment designs over the years would demonstrate.

    Reply 6; Injury prevention in children is seen as a societal concern and for this reason we have the US Consumer Safety Improvement Act, the Canadian Consumer Product Safety Act and the European Consumers Directives, which all include products destined for play by children. These all require the prevention of “Serious injury or Serious risk” which is AIS 3 and not even close to the injury thresholds provided for in playground standards. Moving from AIS >4 down to AIS >3does not gain compliance to the laws and regulations even through it is a move in the right direction. Interestingly the EN1177 states “a HIC of 1000 is equivalent to a 3% chance of critical injury (MAIS 5) and 18% probability of a severe (MAIS 4) head injury. The Hayes Forensic Engineering Group found that for those diagnosed with AIS>5 53.1-58.4% died and AIS>4 7.9-10.6% died. The referenced “shift in thinking” is an adult, governance discussion and we cannot expect children to make informed decisions regarding the threshold of injury they are willing to sustain.


  3. Here are comments to each of Prof. Ball’s items

    Reply 1; ASTM has been moving toward this change for the past 10 years. This is not in isolation of the review of the failure of international standards to meet their stated scopes to protect children from harm at a level of fatality or debilitating injury. 1000 HIC has been demonstrated to have a 10-15% risk of death as outlined in CEN/TR 16148, Head and neck impact, burn and injury criteria – A Guide for CEN helmet standards committees 10% risk of skull fracture, as demonstrated by Harold J. Mertz in 1997. The CEN/TR 16148 also points out that a Peak Acceleration (g) of 100-150g results in Abbreviated Injury Scale (AIS) of 2 and 150-200g is AIS 3. AIS 2 is major laceration or minor blood loss to the scalp, contusion, laceration, loss of cranial function, unconscious for 20% or total scalp loss, swelling, contusions, hemorrhage of the brain, 1-6 hours unconscious or 4 down to AIS >3does not gain compliance to the laws and regulations even through it is a move in the right direction. Interestingly the EN1177 states “a HIC of 1000 is equivalent to a 3% chance of critical injury (MAIS 5) and 18% probability of a severe (MAIS 4) head injury. The Hayes Forensic Engineering Group found that for those diagnosed with AIS>5 53.1-58.4% died and AIS>4 7.9-10.6% died. The referenced “shift in thinking” is an adult, governance discussion and we cannot expect children to make informed decisions regarding the threshold of injury they are willing to sustain.

    Reply 7; The failure here is in taking ISO 31000 as the lead document for risk management when there are documents at the ISO level that specifically related to children such as ISO Guide 50, Safety aspects – Guidelines for child safety in standards and other specifications, which has been in circulation for more than 15 years, or ISO Guide 51, Safety aspects – Guidelines for their inclusion in standards. Specifically Guide 50 states under relevance of child safety.
    “Child safety is a major concern for society, because child and adolescent injuries are a major cause of death and disability in most countries. The joint WHO/UNICEF World Report on Child Injury Prevention[21] identifies unintentional injury as the leading cause of death for children over the age of 5. More than 830 000 children die each year from road traffic crashes, drowning, burns, falls and poisoning.

    Children are born into an adult world, without experience or appreciation of risk but with a natural desire to explore. They can use products or interact with environments in ways not necessarily intended, which are not necessarily regarded as “misuse”. Consequently, the potential for injury is particularly great during childhood. Supervision might not always prevent or minimize significant injury. Therefore, additional injury prevention strategies are often necessary.

    Intervention strategies aimed at protecting children recognize that children are not little adults. Children’s susceptibility to injury and the nature of their injuries differ from those of adults. Such intervention strategies ideally also consider reasonably foreseeable use of products or surroundings. Children interact with them in ways that reflect characteristics of child behaviour, which will vary according to the child’s age and level of development. Intervention strategies intended to protect children therefore often differ from those intended to protect adults.”

    Both Guide 50 and 51 define harm as “injury or damage to the health of people, or damage to property or the environment”, and Guide 51 defines reasonable foreseeable misuse as “use of a product or system in a way not intended by the supplier, but which may result from readily predicable human behaviour” and note 1 provides – “Readily predictable human behaviour includes the behaviour of all types of human beings, e.g. the elderly, children and persons with disabilities.”

    Failure to take the user of the play structure or play environment as a child rather than imposing adult experience and conclusion on the child it to provide a failed play provision.

    Reply 8; No one is saying that play is one of the most important activities in a child’s life, the point is they must survive the play experience. ISO Guide 51 explains that standards, formal or informal, must determine an injury threshold that is acceptable to society and then prevent that harm through the removal of hazards and hazardous situations. The En1176, ASTM F1487, CSA-Z614, CPSIA, CCPSA, EU Consumer Directives, have laid out the societal thresholds as from worst to least, prevention of death or fatality, debilitating injury, serious injury and serious risk. The HIC of 1000 outcome risk does not meet any of these thresholds and the benefits of play will be lost to those children who are unfortunate enough to experience this 1000 HIC performance.

    Reply 9; Again no one is saying that challenge should be eliminated from the playground. This is how the child learns their own abilities, expands their capabilities and engage with their peers to complete a particular challenge. However asking a child to perform risk analysis is misguided in the context of documents being quoted. Guide 51 defines risk analysis as “systematic use of available information to identify hazards and to eliminate the risk” and risk reduction measure as “any action or means to eliminate hazards and reduce risk”. Given that measurement of the impact attenuation of the surface is performed with a sophisticated electronic device with accelerometers, digital filters and complicated software or that once the testing is performed no standard provides labeling the height to which a surface performs to, even though it was a recommendation of the COMSIS Corporation in 1990, how is the child or better still the parent or other adult caregiver to even start the “exposure to risk” that is presented. Saying that we are “dumbing down” the playground by allowing or hiding hazards in at best negligent and at worst abuse.

    Reply 10; Playgrounds are built in the premise of providing age-appropriate challenge and that is why standards clearly state the age group the structures are intended. In North America, for public playgrounds, this is 2 years to 12 years, while in Europe the EN1177 is to protect children, which is Guide 50 are defined as being 0-14 years. In North America there is a very clear requirement that each play structure have a permanently affixed label outlining the age 2-5 or 5-12 that it is intended for. The fact that other people might be using the play environment is outside the scope of the standards and if the user is older, they might be better able to make some risk assessment or if they are younger than 2 they are likely to be attended by an adult parent or caregiver also more capable of some risk assessment.

    Reply 11; Obviously we will learn from our experiences and make changes to our environments that enhance quality of life for all both in personal growth and prevention of injury.
    Reply 12; The lowering of the HIC from 1000 to 700 takes into consideration the need to provide challenging play. There is nothing in the ASTM proposal to limit play or play value. There is no limit to the height of play structures as in Europe, just the requirement that when the fall occurs from the height the child falls from, the injury risk is less than AIS>4. Although many suppliers provide both a line of play structures and protective surfacing options, the blending of the two is the concern. In Europe (to belabor the point) the EN1177 states “a HIC of 1000 is equivalent to a 3% chance of critical injury (MAIS 5) and 18% probability of a severe (MAIS 4) head injury. The Hayes Forensic Engineering Group found that for those diagnosed with AIS>5 53.1-58.4% died and AIS>4 7.9-10.6% died.

    Reply 13; There is no argument that HIC is a complicated, sophisticated and elegant formulation that needs considerable computing power. The ASTM F1292-93, which introduced HIC also provided a 6 page appendix for the computer program required to calculate the HIC. From immediately above the HIC of 1000 is a 15% risk of severe (AIS>4, life-threatening with survival probable) and from ASTM F1292-04 an HIC of 500 is a 79% risk of a minor head injury and a 38% risk of a moderate head injury. First the 1000 again exceeds that stated scopes of all of the playground standards around the world. In the medical world there is a huge difference between minor, moderate, serious, severe and critical head injuries, that is why the categories exist.

    Reply 14; If there is ambiguity, it is at a number of levels in the information. The standards state their scope as being the prevention of fatality, life-threatening, and debilitating injuries. Anyone can go on the internet to the appropriate standards organization and for free get a copy of the scope and reading the stated injury threshold be satisfied that having their child play on a playground that is compliant to the standard will prevent a level of injury. Nowhere is there a clear discussion of the risks a parent will put their child at other than is the Appendixes of ASTM F1292 (page 17). If there is ambiguity, it is in not using plane language and then mixing the injury risk that is higher as being acceptable.

    Reply 15; We are not talking about a 15% risk of TBI. King and Ball (1989) stated below 50 g one can be fairly confident no permanent brain injury would occur. That is a far cry for 200 g and 1000 HIC. We are talking about a 15-16% risk of AIS>4 and 10% risk of skull fracture. To trivialize this, particularly in relation to the reference to the “much circulated paper”, is clearly a disservice to the injury prevention community.

    Reply 16; The first and foremost injury prevention is that of the head injury as this can have significant and long-term consequences. Since long-bone injury resulting from a fall and landing on the surface will be the result of both the magnitude of the force and the speed of loading, any improvement in the impact attenuation of surfacing will lower the magnitude. The speed of loading is also a function of velocity or the height from which the child falls. That is why testing of playground protective surfacing is to be from the height a child is expected to fall.

    Reply 17; Children have died recently from head injuries sustained falling the playground. It is ludicrous to think that one of a few deaths are okay and therefore the severity of all other injuries are also ok. Again, the standards have a state scope and 1000 HIC does not make it. Also suggesting that impact absorbing surface is expensive would suggest that a little is more than none. The predominate surface in the United States is Engineered Wood Fiber (EWF) that has a very low cost and depending upon the installation technique and the maintenance can be made to meet the requirements of the ADA. Therefore the cost of the change is negligible and when considering that the addressable annual cost of injuries in playgrounds in 2002 as stated in a 2004 CPSC Hazard Screening Report for the United States was approximately US $8.2 BILLION, any change that can reduce severity of injury is well worth the change.

    When we are supposedly considering cost, while there is nothing said about the adoption and cost of swing seats at 50g. Previously there was the wooden swing as a single user seat and it was decided by one manufacture that to get to what King and Ball (1989) stated that below 50 g one can be fairly confident no permanent brain injury would occur, they would produce a swing and this was advanced all the way to AIS 1 passing AIS 2, 3, 4 and 5 and not a mention of the cost of these swing seats along the way. Where were the complaints on cost when this was adopted in 2008 into EN1177-2, moderating of eliminating a maximum of 3% of playground injuries while ignoring 72-78% of the injuries related to falls to the surfaces.

    Reply 18; Effectively the overall benefit is raised through the provision of play equipment that provide challenge and play value for children and reduction of injury will reduce unwarranted suffering and reduce costs. The change from 1000 HIC to 700 is a playground win all around.


    • Rolf,

      There is no question that ‘evidence’ has a critical role to play when considering how the health and well-being of children and teenagers might best be secured. And you have offered a veritable cascade of ‘evidence’ that persuades you to support the proposal to reduce HIC values from 1000HIC to HIC700.

      To be clear, there is, I think, no dispute that ‘evidence’has an important role to play in reaching decisions about, in this case, whether a reduction in HIC values is justified. But that position is insufficient in itself to reach an informed, reasonable decision. In brief, as the papers of Professor Ball and the BC Research and Prevention Unit adequately demonstrate, what counts as evidence require critical scrutiny, the ‘facts’ do not simply speak for themselves – their relevance and applicability are not ‘givens’ but matters for consideration.

      The question here is ‘what counts as evidence’, and what weight it should be accorded, in the matter we are discussing.
      Many will want to question, for example, whether it is in fact straightforwardly obvious that tests on the effects of acceleration and impact using non-human primates, cadavers and the brave, but perhaps foolhardy, Colonel Stapp can simply be read across to children and teenagers behaviours at play.

      Then there are the wider, value-based considerations that form the context, the framework, within which decisions about ‘acceptable levels of risk’ must be taken. These include,but are not limited to, the risks that society is prepared to tolerate because of the potential benefits that accrue from potential exposure to those risks. Thus, the prevention of accidents and injuries is only one goal among many, and a too narrow and uncritical focus on that goal may in practice limit or prevent access to other, significant benefits.

      What is clear is that what counts as evidence, its meaning and applicability, and the context within which it should judged, is in dispute. Authoritative, informed voices have raised questions about the ‘evidence’. Those authoritative voices go beyond those named above and include, for example: those who daily work with children and teenagers in play settings; those who design play settings; educators; psychologists; the British Standards Institute; the International School Grounds Alliance; the UK Play Safety Forum, to name but a few.

      In the light of this, it seems to me hard to deny that it is reasonable to demand – and unreasonable not to acquiesce to the demand – that before a decision is made about HIV values that, in the words of the International School Grounds Alliance, in accord with the UK Play Safety Forum that:

      ‘…a proper, impartial, publicly available review of the proposal is undertaken before any conclusion is reached as to the desirability of the proposed reduction in HIV values. Such a review should include:

      • a clear statement of aims of the measure / intervention

      • the scientific evidence

      • an account of the financial costs of the measure and who would bear them

      • a comprehensive risk-benefit analysis including consideration of wider implications e.g. effects on play value, health and well
      being of children and the probable effects on the amount of play provision.

      A decision should then only be taken after comments have been received, published and considered by a wide range of stakeholders.

      Would you not agree?


  4. Pingback: Can we go too far when it comes to children’s injury prevention? - BC Injury Research and Prevention Unit

  5. I would also like to reblog this on accessibleplayground.net This is such an important issue for people dealing with disabilities. If we limit the types of surfacing because of increased cost or because they no longer meet regulations, we will have less and less playspaces that welcome everyone. Please let me know at mara@letkidsplay.com if I have permission. Thank you!


  6. Reblogged this on Rethinking Childhood and commented:
    This post shares a most helpful paper on playground surfacing from David Ball, Professor of Risk Management and a long-term collaborator of mine. It is taken from the website of our mutual collaborator Bernard Spiegal.
    As Bernard says, the value of David’s paper is that it places the playground surfacing debate in the wider context of social values and policy. What is more, it does this in a clear, concise, balanced and thoughtful way. It also offers some helpful historical insights. It should be of interest to anyone who wants to get a wider perspective on this complex topic.


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