RECURRENT SYSTEMIC SLIPS?
Richard Bowman
Intertile Research, 32 Robinson Street, Brighton East, VIC 3187, Australia

In reviewing recent developments in slip resistance standardisation and building
regulation proposals, it becomes obvious that there are many reforms that still need
to be made in order that premises remain sufficiently slip resistant throughout
economically reasonable working lives. When will bureaucrats stop slipping up?

Introduction
Should minimisation of slip-related injuries be a global priority? Has anyone determined how
many non-occupational falls on the level are due to environmentally caused slips, having
determined the available traction, and at the time of the incident? Has any country benchmarked
the available traction that is available in publicly accessible and residential settings? The European
Union has sensibly legislated that floors should be safe at the end of an economically reasonable
working life, but which flooring providers can reliably indicate the anticipated long term slip
resistance of floor finishes over multiple environmental usage scenarios? Since slip resistance will
decrease due to wear and soiling, do published recommendations for new floors overestimate therequired slip resistance? Can mandated floors be cleaned as expected? What guidance exists forthe realistic interpretation of slip resistance audits? Many residential and hotel bathrooms have a
wet coefficient of friction of less than 0.18 – if the theoretical risk of slipping is 1 in 2 when
walking on a level surface with a coefficient of friction of 0.19, why do relatively few bathroom
accidents occur? Is there a realistic scientific basis for establishing slipping risk that factors in
relevant accidental circumstances? Do expert reports in litigious matters provide sufficient
information to help judges make appropriate decisions? When most falls in the elderly are related
to biomedical causes, are governments well advised when told the elderly need highly slip resistantfloors (that promote stumbles)? Is government falls prevention research funding sensibly directed?
Surely slips and falls conferences should start to focus on some of the bigger issues in order todevelop collaborative research efforts? What, if anything, is done differently now than five or ten
years ago? If we were to address the recurrent public slip resistance challenges what initiatives
should be implemented?

The Cost of Slips, Trips and Unintentional Falls and the Regulators’ Responses
The high costs of falls injuries has caused Governments great concern due to a perception of
epidemic hospitalisation costs associated with the ageing of the population. Significant funding
has been provided to delay the onset of biomedically induced falls, essentially trying to improvethe balance, strength and fitness of the elderly, through voluntary participation in appropriate
activities. Limited home modification assistance has also been provided so people can remain at
home, but any associated slip resistance evaluations are subjective rather than objective.

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The Australian Building Codes Board (ABCB) commissioned Monash University Accident
Research Centre (MUARC) to undertake a study of the incidence of slips, trips and falls and thedesign and construction of buildings. Ozanne-Smith et al (2008) produced MUARC report 281,
“The relationship between slips, trips and falls and the design and construction of buildings”.
While this was a useful first step in publicly understanding the dimensions of the problem andcosts of falls in Australia, the epidemiologist researchers and the project’s ‘expert panel’ lacked
specialist slips, trips and falls expertise. Such expert knowledge should have identified thecritical issues that might then have enabled the ABCB to best determine the provisions thatwould reduce slips trips and falls in buildings. Hence the understanding necessary to improve
the safe use of buildings is still missing, as well as some required data.
The most common falls hazards MUARC identified included: the wide range of allowed
stair riser/going measurements and the often insufficient illumination found in many domestic
stairways; the possible absence of handrails for stairways in domestic buildings; and a lack ofdefinitive measurement or requirement for slip resistance for flooring surfaces.
In 2010, the ABCB proposed five falls prevention changes to the Building Code ofAustralia (BCA) including a handrail requirement in private stairways; and stair riser and going
dimensions to be subject to a narrower range with a minimum going of 280 mm. A regulatory
impact statement (ABCB, 2011) only found the new handrail requirement to be cost effective.
Ozanne-Smith et al (2008) identified that 80% of stair accidents occur during descent andthat the narrow going width currently permitted by the BCA could potentially encourage falls
during descent. However, they found little detailed relationship between slips, trips and falls andthe design and construction of buildings. The available Australian accident data was predictably
pitiful from a falls prevention perspective: hospitals seek and keep no data on stair geometry intheir case files. The ABCB (2011) concluded that “No research has been conducted to identify
the contribution that individual building components make to the incidence of slips, trips andfalls relative to other contributing factors or how specific changes to some building components
can reduce the incidence of slips, trips and falls”. Although regulators need to identify the extent
of fall and injury reduction that can be attributed to any proposed change, Ozanne-Smith et al(2008) failed to include the need for such research in their recommendations.
While Ozanne-Smith et al (2008) referenced the work of Roys & Wright (2003), they failed
to highlight its most significant findings: “The effect of going size on slipping is so dramaticthat it should be possible to walk with a reduced chance of slipping, even on highly
contaminated stairs, if the going is large enough”; and “Where the going is less than 300 mm,
the material and design of the nosing contributes to the likelihood of a slip”.
When walking down stairs, the first contact between the shoe and the step is with the toes or
midsole of the shoe. An overstep is twenty thousand times more likely to occur when the goingis 250 mm compared to 325 mm. Although it can be calculated {based on Roys & Wright(2003)} that an increase in the going from 250 to 280 mm should reduce the incidence of large
oversteps by 94%, the effectiveness of the stair riser and going dimensions proposal was
assumed to be only 30% (ABCB, 2011) although no data was provided to support thisassumption. Even though 63% of new residential stair goings appear to be less than 280 mm (DiMarzio, 2010), the proposal for a minimum going to 280 mm was dismissed on the perceived
cost benefit analysis (ABCB, 2011). Expert reanalysis of the data by a falls specialist would
seem most appropriate. The only successful (handrail) proposal was assessed with an assumed
30% effectiveness, where that assumption was based on a published study.

Stair Nosings

Since the ABCB has dismissed the stair geometry proposal, the pressure for stair safety is now
literally on the stair nosing, and how its slip resistance may change due to wear, even if these
aspects might not be effectively determined by the new Australian slip resistance standards.
The highest risk of a dangerous slip occurring on a stairway will generally be due to that ofoverstepping of a nosing during stair descent, particularly when the stair has a high pitch (highrisers and short goings). As the going decreases, it becomes harder to place a substantial part of
the foot on the step, leading to potential oversteps in descent. With goings less than 300 mm,- 184 -

people tend to rotate their feet in descent to ensure that enough of the foot remains on the tread.
However, some continue without sufficiently rotating their feet on stairs with smaller goings;
this increases the amount of overhang and hence the risk of slipping. While there are various
nosing geometries, the position of slip resistant nosing should extend from the step tread up to
the vertical front face of the nosing, as Hunter (2013) has confirmed.
The ABCB (2013) now proposes to quantify “slip resistance”. The proposed changes to“slip resistance” also apply to the terms “nonslip”, “non-skid” and “slip-resistant” in the
National Construction Code (NCC) – the new title of the BCA. It is proposed that the existing
slip resistance code requirements for stairways, landings and ramps be changed from the format“The surface of a {ramp} must have a non-slip finish” to “The surface of a {nosing strip} musthave a slip-resistance classification complying with Table 1 when tested in accordance with AS
4586”. The nosing strip requirement would apply to all building classes and stair geometries. Achange to the wording “The surface of a {nosing} must have a non-slip finish (such as a slipresistance classification complying with Table 1 when tested in accordance with AS 4586)”
would sensibly allow appropriate alternative design solutions, such as longer goings, contrasting
nosings and safer illumination provisions. This phrasing would also enable recognition andapplication of the work of Hunter (2013) on nosings, a term that the ABCB has yet to define.
Table 1 Proposed NCC 2014 Slip-Resistance Classifications
Application
Surface conditions
Dry
Wet
Ramp steeper than 1:14
P4 or R11
P5 or R12
Ramp not steeper than 1:14
P3 or R10
P4 or R11
Tread or landing surface
P3 or R10
P4 or R11
Nosing or landing edge strip
P3
P4

New Australian Standards
AS 4586:2013, Slip resistance of new pedestrian surface materials, and AS 4663:2013, Slip
resistance measurement of existing pedestrian surfaces, have both adopted the use of lapping
film for preparing the rubber test feet. This provides better differentiation between surfaces atthe slippery end of the slip resistance spectrum, since the floor surface results are no longer
dominated by the rubber slider roughness. The old class X products (35 - 44 BPN) will now
variously fall into new classes P3 (35 - 44 BPN), P2 (25 - 34 BPN) and P1 (12 - 24 BPN). In
practical terms the difference between a P3 floor surface that has a 35 BPN mean and a P2 floor
surface that has a 34 BPN mean, in terms of the risk of someone slipping over, is virtually nil.
Yet there is a real risk that the proposal will declare there to be a significant difference.
Merchants and consumers have still to re-educate themselves that some class X products
they perceived as being safe are unlikely to now be regarded as safe, even though their intrinsic
slip resistance remains the same. The converse view is that this reorientation explains why slips
would sometimes occur on products that were deemed safe ( 39 BPN) by AS/NZS
3661.1:1993, Slip resistance of pedestrian surfaces: Requirements. AS/NZS 3661.1 is still thebasis of the slip resistance provisions in the New Zealand Building Code. However, theAccident Compensation Corporation (ACC), which provides comprehensive, no-fault personal
injury cover for all New Zealand residents and visitors to New Zealand, is currently
investigating “good practice” for testing the slip resistance of bathroom and kitchen flooring.
Since class P3 might be regarded as non-slip and class P1 as noticeably slippery, the greater
differentiation between ‘non-slip’ and ‘slippery’ products will enable new design guidance to beprovided. However, Standards Australia Handbook 197 (Bowman, 1999) is still current (with its
dubious notional interpretations of the “contribution of the floor surface to the risk of slipping
when water wet”.
The proposed Table 1 (above) would require a product to have either a R10 oil wetclassification or a wet pendulum class P3 (35 - 44 BPN) for a dry residential stair tread surface- 185 -

(that is not normally wet or likely to be made wet by an accidental spill). While either option
appears excessive, class R10 products have been found to yield pendulum classifications fromP5 (ш 55 BPN) to P1. Given that the pendulum is used to conduct audits and accident
investigations, it is somewhat nonsensical to rely solely upon oil wet ramp classifications for
public locations (and particularly private homes) where smooth soled footwear is worn. The oil
wet ramp test requires the use of profiled footwear to determine the physical-interlock-slipresistance. Singular reliance on oil wet ramp classifications entails a frequently observed riskthat pendulum results would subsequently indicate a specified product was never fit for its
intended purpose.
AS 4586 still requires that stair nosings and treads be tested in a direction that is normal toany strips, grooves and profiles, even though a similar requirement for tactile ground surface
indicators (TGSIs) has been amended to require an offset of 10 degrees to prevent grooving of
the rubber test feet when testing linearly profiled directional TGSIs; and an offset of 30 degrees
to ensure that only the chamfered edge of the rubber test foot contacts the warning TGSIs.

Figure 1 A castellated metallic stair nosing
Figure 1 shows a castellated metallic stair nosing that rapidly grooves and shreds Four S rubber
test feet (slider 96), such that the nosing needs to be tested at an offset angle in order to getreliable consistent results. There are other hard ribbed nosing profiles that also destroy thechamfered edges of pendulum test feet. While manufacturers may engineer nosing and tread
designs in order to obtain high slip classifications, pendulum testing is based on the principle oftesting in the direction that gives the lowest results. There is an unstated assumption that any
testing will be consistent with the correct pendulum operational principles, where the rubber test
foot condition is fundamental to the hydrodynamic theory of squeeze film formation.
AS 4586 also now allows carpets to be tested with the pendulum in both wet and dry
conditions. While it is desirable that other surfaces should also be permitted to be tested with thedry pendulum, the use of the wet pendulum classifications for the dry carpet pendulum test
results is mystifying: materials that have very low wet pendulum results typically have dry
results that are much higher than materials that have high wet pendulum results. Although dry
results are best considered in the context of wet results, separate classification schemes are
required to avoid any confusion between P5 and P5dry.

Specification of slip resistant pedestrian surfaces
The European Construction Product Regulations (CPR) now require that products will be safe
(i.e. slip resistant) at the end of an economically reasonable working life. This position
recognises that slip resistance tends to decrease, and is consistent with occupational health andsafety (OHS) needs and sensible risk management practices.
Various approaches can be taken towards specifying the slip resistance of pedestriansurfaces. The German occupational health and safety (OHS) system requires that new workplace
floors comply with prescribed oil wet ramp slip resistance and volumetric displacement
requirements. These requirements were published as recommendations in Standards Australia- 186 -

Handbook 197 (Bowman, 1999). Unfortunately some flooring manufacturers have chosen toignore the volumetric displacement requirements, overlooking the fact that German practice isto require a higher classification if the volumetric displacement requirements are not fulfilled.
HB 197 also makes some recommendations for new floors in terms of the now superseded
pendulum classifications. These recommendations contain some safety factor, to allow for slip
resistance lost due to the polishing wear of foot traffic, although the amount of slip resistancelost varies considerably between materials. This causes over-specification of slip resistance:
property owners have difficulties cleaning floors that are rougher than desired, whereupon
aggressive cleaning practices can then significantly reduce the inherent slip resistance.
Another approach is to specify a minimum long term performance requirement based on the
anticipated use of a facility and the intended risk management approach, bearing in mind thatthe slip resistance of the floor is only one component of safe pedestrian surface design. Thus if
25, 30 or 35 BPN was specified as the nominal limit for an area in service, a manufacturer
would need to indicate that a product would have sufficient slip resistance at the end of areasonable working period, on the basis that the floor would be maintained in accordance with
their instructions. This minimum acceptable slip resistance approach provides a basis forinterpreting periodic audits. As the floor nears the specified limit, any workplace controller must
obviously obtain staff feedback to ensure that existing safety provisions are adequate, whereby
values less than the specified limit might be found to be acceptable.
Appropriate accelerated wear tests (AWT) can provide a basis for determining the likely
long term slip resistance. Such tests need to be standardised where pads that contain highlyabrasive media need to be used with caution. There has been some European research using
commercial scouring pads for accelerated wear conditioning of ceramic tiles, even though one
would not expect these pads to be used for tile maintenance procedures, Bowman (2012).
Building codes should not rely on regulations that provide transitory slip resistance for newbuildings. They should require economically reasonable life cycle slip resistance performance.
It is anticipated that in 2014 the ABCB will propose mandatory slip resistance for most floors.

Interpreting Slip Resistance Test Data
With the change in rubber test foot preparation, the slip resistance of some polished porcelaintiles has fallen from 26 to 11 BPN, i.e., from class Y (25-34 BPN) (that was considered too
unreliable to use in terms of HB 197 recommendations) to P0 (< 12 BPN). While the measured
slip resistance may have fallen, the inherent slip resistance is unchanged. Such tiles would havebeen considered to make a high contribution to the risk of slipping when water wet, or a very
high risk (20 BPN) in the unlikely event of 100 cycles of AWT being commissioned.
Should Australia now adopt the UKSRG (2011) criteria, for high (< 25 BPN), moderate(25 – 35 BPN) and low (> 35 BPN) slip potential? These criteria were based on Pye’s analysis(1994). This suggested that for unencumbered, reasonably active pedestrians aged between 18
and 60, a pendulum result of 36 BPN or above represented an acceptably low risk (one in a
million) of slipping when walking in a straight line on a level surface. A 24 BPN result has beenequated with a risk of 1 in 20, and 20 BPN with a risk of 1 in 5. Since much lower results would
seemingly predict epidemic accident levels (that have not occurred), do such analyses provide
an appropriate basis for determining slip resistance design (or liability in the case of accidents)?
Burnfield & Powers (2003) determined mean peak utilised coefficient of friction (COFU) fora medium walking pace was 0.23 for men and 0.24 for women. The considerable difference
between their data and that of the Building Research Establishment {0.17 for men and 0.16 forwomen, Harper, Warlow & Clarke (1961)} is probably due to measuring protocols. Burnfield &Powers found the peak COFU for their 60 subjects ranged from 0.13 to 0.44 when walking fast.
Chang, Matz & Chang (2013) have undertaken extensive new walking trials and force platestudies, where their calculated statistical slip probabilities differ slightly from those of Pye.
There is a 5% risk of slipping with a 0.26 COF for people under the age of 55, and a 0.25 COF
for people over the age of 55. How do we best apply these findings to real world situations?

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Since the mean slip resistance in many domestic bathrooms has been determined to provide
available traction of 0.12 to 0.17 COF (13 to 18 BPN according to AS/NZS 4663:2004), and AS
4586 and AS 4663 will tend to yield results lower than these, why aren’t more residents fallingover? The residents have obviously modified their gait and reduced their traction demand. Since
they are no longer walking freely (as asked of the force plate study subjects) the analyticaloutcomes of such free walking studies rapidly become of diminished relevance in residential
settings, where familiarity with the surroundings induces gait restraints.
Closing remarks
Why so many introductory questions and so few definitive answers? Sometimes we need to ask
many questions to determine we know the real facts, rather than assuming that some seemingly
established facts are universal truths. While nations should invest funds to protect their elderly
from biomedically induced falls, there should be a greater investment in protecting the wholecommunity from environmentally caused accidents, as there is a far greater cost associated withthe temporary and permanent disability of younger productive people, particularly workers andhome carers. If only Governments were to seek to become better informed about how tointerpret slip resistance and falls related data when investing funds and drafting regulations.

References
ABCB (2011). Regulation Impact Statement for a Proposal to revise the Building Code ofAustralia to reduce the risk of slips trips and falls in buildings. Australian Building Codes
Board. June 2011.
ABCB (2013). Overview of proposed changes for slip resistance. Australian Building Codes
Board. Retrieved August 8, 2013, from http://www.abcb.gov.au/~/media/Files/Download%
20Documents/Consultation/NCC2014/Slip-Resistance_Note%20for%20PCD.pdf.
Bowman, R. (1999). An Introductory Guide to the Slip Resistance of Pedestrian Surface
Materials.Standards Australia Handbook 197: 1999.
Bowman, R. (2012). Slip resistance – planning for a green future. In Proceedings of the 12th
World Congress of Ceramic Tile Quality. Retrieved August 8, 2013, fromhttp://www.qualicer.org/recopilatorio/ponencias/pdf/2012216.pdf.
Burnfield, J.M., & Powers, C.M. (2003). Influence of age and gender on utilized coefficient offriction during walking at different speeds. In Metrology of Pedestrian Locomotion and Slip
Resistance, ASTM STP 1424: pages 3-16.
Chang, W.R., Matz, S. & Chang, C.C. (2013). The available coefficient of friction associatedwith different slip probabilities for level straight walking. Safety Science, 58, 49-52.
Di Marzio Research Pty Ltd (2010). Trips, Slips and Falls Project prepared for Australian
Building Codes Board. Study No. 10/02/1355, February 2010.
Harper, F.C., Warlow, W.J. & Clarke, B.L. (1961). The forces applied to the floor by the foot inwalking: Walking on a level surface. National Building Studies Research Paper 32, HMSO.
Hunter, R.A. (2013). Contribution of Nosing Shape, Nosing Texture and Tread Texture to
Stairway Slip Resistance. In Proceedings of International Conference on Fall Prevention
and Protection 2013.
Ozanne-Smith, J., Guy, J., Kelly M. & Clapperton A. (2008). The relationship between slips,
trips and falls and the design and construction of buildings. Monash University Accident
Research Centre Report No. 281.
Pye, P.W. (1994). A Brief Review of the Historical Contribution Made by BRE to Slip
Research. In Slipping – Towards Safer Flooring, Paper 7, Seminar held at Rapra
Technology Ltd, Shawbury, Shrewsbury, England, 29 September 1994
Roys, M. & Wright, M. (2003). Proprietary nosings for non-domestic stairs, (BRE IP 15/03),
Building Research Establishment, UK, October 2003
UKSRG (2011) The Assessment of Floor Slip Resistance – The UK Slip Resistance Group
Guidelines. UK Slip Resistance Group.

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