ASTM F2508-11
(Practice)Standard Practice for Validation and Calibration of Walkway Tribometers Using Reference Surfaces
Standard Practice for Validation and Calibration of Walkway Tribometers Using Reference Surfaces
SIGNIFICANCE AND USE
To be meaningful, walkway tribometer results must correlate the slip characteristics of a surface or contaminant, or both, to the actual propensity for human slips. To achieve this goal, walkway tribometer models must be validated against a standard with relevance to human ambulation.
This practice prescribes a series of reference surfaces with known relative slip potential ranging from very high to low (as defined by laboratory conditions only) upon which walkway tribometer models can be validated. The relative slip potential of each reference surface was established from human subject walking trials.
The following should be considered in applying the validation and calibration obtained by this practice:
The scientific study upon which the validation process is based was conducted with a select population of young adults (mean age 26 years) who were free from gait deviations while walking in a straight path on a level surface with a mean walking velocity of 2.18 m/s. This walking velocity is faster than the average walking velocity for the general population which includes a much wider age range with greater variability; thus, the study sample population of pedestrians and conditions is not representative of the larger general population of pedestrians.
All subjects walked in Oxford-style shoes whose soles were constructed of smooth styrene butadiene rubber (SBR) with 75A Shore hardness. The shoe style and sole material is not representative of all combinations available in the marketplace.
The reference surfaces defined in this practice are not representative of all walkway surfaces. The outcome of the validation practice reflects performance on the type of reference surfaces and surface conditions defined in this practice only. Validation and calibration of a walkway tribometer as defined by this practice does not imply validation and calibration under all combinations of test foot materials and walkway surfaces.
The validation and calibration proced...
SCOPE
1.1 This practice is intended to establish the parameters for validation and calibration of walkway tribometers.
1.2 This practice provides a walkway tribometer supplier with a procedure and suite of reference surfaces to validate his walkway tribometer by properly ranking and differentiating the surfaces.
1.3 This practice provides the user of a walkway tribometer with a procedure and suite of reference surfaces to test calibration of his instrument.
1.4 This practice describes the necessary materials, specifications, and the cleaning process for reference materials, as well as the requirements for the validation of a supplier’s walkway tribometer and calibration of a user’s walkway tribometer.
1.5 This practice applies to walkway tribometers without reference to the nature of the scale of the readings produced by them. The scale used in the reports of validation and calibration must be the same, and are to be those of the instrument or defined for the instrument.
1.6 The values stated in SI units are to be regarded as standard. The values given in parentheses are for information only and are not considered standard.
1.7 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: F2508 − 11 AnAmerican National Standard
Standard Practice for
Validation and Calibration of Walkway Tribometers Using
Reference Surfaces
This standard is issued under the fixed designation F2508; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope D1349 Practice for Rubber—Standard Temperatures for
Testing
1.1 This practice is intended to establish the parameters for
D3244 Practice for Utilization of Test Data to Determine
validation and calibration of walkway tribometers.
Conformance with Specifications
1.2 This practice provides a walkway tribometer supplier
F1646 Terminology Relating to Safety and Traction for
with a procedure and suite of reference surfaces to validate his
Footwear
walkwaytribometerbyproperlyrankinganddifferentiatingthe
surfaces.
3. Terminology
1.3 This practice provides the user of a walkway tribometer
3.1 Definitions:
with a procedure and suite of reference surfaces to test
3.1.1 For terms used in this practice not identified herein,
calibration of his instrument.
refer to Terminology F1646.
1.4 This practice describes the necessary materials,
3.1.2 paired t-test, n—a test of statistical significance based
specifications,andthecleaningprocessforreferencematerials,
on the use of student’s t-distribution and used to compare two
as well as the requirements for the validation of a supplier’s
sample means (see Appendix X2).
walkway tribometer and calibration of a user’s walkway
tribometer. 3.1.3 supplier, n—any individual, agent, company,
manufacturer, or organization responsible for the walkway
1.5 This practice applies to walkway tribometers without
tribometer prior to receipt by the user. D3244
reference to the nature of the scale of the readings produced by
them.Thescaleusedinthereportsofvalidationandcalibration
3.1.4 test foot, n—shoe bottom material or surrogate
must be the same, and are to be those of the instrument or
mounted on the walkway tribometer that comes into contact
defined for the instrument.
with the surface being tested.
1.6 The values stated in SI units are to be regarded as
3.1.5 walkway tribometer, n—any apparatus used to mea-
standard. The values given in parentheses are for information
sure the frictional forces acting at an interface between a
only and are not considered standard.
walkway surface and shoe material.
1.7 This standard does not purport to address all of the
3.1.5.1 Discussion—A judgement of the adequacy of these
safety concerns, if any, associated with its use. It is the
frictional forces acting on a walkway surface/shoe surface
responsibility of the user of this standard to establish appro-
interface is the basis for an assessment of slip properties
priate safety and health practices and determine the applica-
relative to human locomotion.
bility of regulatory limitations prior to use.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 calibration, n—the set of operations that establishes,
2. Referenced Documents
under specified conditions, the relationship between the values
2.1 ASTM Standards:
obtained by a walkway tribometer and the corresponding
supplier reference values.
1 3.2.2 reference surfaces (RS’s), n—specifiedmaterials,iden-
This practice is under the jurisdiction ofASTM Committee F13 on Pedestrian/
Walkway Safety and Footwear and is the direct responsibility of Subcommittee tified in Section 7, that have an experimentally demonstrated
F13.10 on Traction.
slip properties for a select population of pedestrians and serve
Current edition approved March 15, 2011. Published March 2011. DOI:
as references for walkway tribometer measurements.
10.1520/F2508-11.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
3.2.3 validation, n—the set of operations that establishes,
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
under specified conditions, the proper ranking and differentia-
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. tion of reference surfaces by a walkway tribometer.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F2508 − 11
4. Summary of Practice ity; thus, the study sample population of pedestrians and
conditionsisnotrepresentativeofthelargergeneralpopulation
4.1 This practice establishes a procedure to: (1) validate
of pedestrians.
walkway tribometer models against a human gait-based refer-
5.3.2 All subjects walked in Oxford-style shoes whose soles
encesystem,and (2)calibrateeachindividualwalkwaytribom-
were constructed of smooth styrene butadiene rubber (SBR)
eters of a validated model against published suppliers’ refer-
with 75A Shore hardness. The shoe style and sole material is
ence values (as defined in 9.1, Eq 4).
not representative of all combinations available in the market-
4.2 This practice provides for validation and calibration of
place.
walkway tribometers as a means of verifying their relationship
5.3.3 The reference surfaces defined in this practice are not
to reference surfaces and verifying a particular device contin-
representative of all walkway surfaces. The outcome of the
ues to produce consistent results.
validation practice reflects performance on the type of refer-
4.3 The method of ranking walkway surface slip properties ence surfaces and surface conditions defined in this practice
only. Validation and calibration of a walkway tribometer as
using a limited population of ambulating human subjects is
supported by a peer-reviewed study. defined by this practice does not imply validation and calibra-
tion under all combinations of test foot materials and walkway
4.4 Validation consists of a series of 40 tests on each
surfaces.
reference surface from this practice. A walkway tribometer
5.3.4 The validation and calibration procedure defined by
model is considered valid if it ranks the four reference surfaces
this practice is not intended to establish a “safe threshold”
from this practice in the proper order with statistically signifi-
value for any walkway surface.
cant differentiation between results obtained for each surface.
Validation is intended to be accomplished for each walkway
6. Apparatus
tribometer model when it is initially introduced and is to be
6.1 The walkway tribometer shall be free of defects and
accomplished by or on behalf of the supplier and made
operational throughout its range. Refer to the walkway tribom-
available to each user.
eter instruction manual to ensure proper operation and instru-
4.5 Calibration for a specific walkway tribometer requires a
ment condition before the validation and calibration process.
series of 16 tests on each of the reference surfaces from this
6.2 Test Foot Designation and Condition:
practice. A specific walkway tribometer is considered within
6.2.1 The supplier must provide test foot material,
calibration if the bias of the mean test values for each surface
dimension, storage, and service life specifications. The speci-
falls within the 95 % confidence interval for the walkway
fications shall be sufficient to permit procurement of an
tribometer model as established by the validation tests (as
exemplar test foot.
defined in 9.1, Eq 4).
6.2.2 Auniquely numbered test foot, meeting the supplier’s
material and dimensional specifications shall be provided with
5. Significance and Use
the walkway tribometer being tested.
5.1 To be meaningful, walkway tribometer results must
6.2.2.1 The calibration results shall apply only to the walk-
correlate the slip characteristics of a surface or contaminant, or
way tribometer/test foot combination tested.
both, to the actual propensity for human slips. To achieve this
6.2.3 Prepare the test foot as prescribed by the walkway
goal, walkway tribometer models must be validated against a
tribometer supplier or by a fully documented procedure in-
standard with relevance to human ambulation.
cluded in the validation or calibration report.
5.2 This practice prescribes a series of reference surfaces
with known relative slip potential ranging from very high to
7. Reference Surfaces (RS’s)
low (as defined by laboratory conditions only) upon which
7.1 Reference Surfaces:
walkway tribometer models can be validated. The relative slip
7.1.1 RS A—Polished black granite whose surface beneath
potentialofeachreferencesurfacewasestablishedfromhuman
the test foot is covered with a continuous film of 0.04 % by
subject walking trials.
volume solution of Triton X-100 (nonionic surfactant) in
5.3 The following should be considered in applying the
distilled water (that is, 200 µL of Triton X-100 per 500 mL of
validation and calibration obtained by this practice:
distilled water).
5.3.1 The scientific study upon which the validation process
7.1.2 RS B—Porcelain whose surface beneath the test foot is
is based was conducted with a select population of young
covered with a continuous film of distilled water.
adults (mean age 26 years) who were free from gait deviations
7.1.3 RS C—Vinyl composition tile whose surface beneath
while walking in a straight path on a level surface with a mean
thetestfootiscoveredwithacontinuousfilmofdistilledwater.
walking velocity of 2.18 m/s. This walking velocity is faster
than the average walking velocity for the general population
which includes a much wider age range with greater variabil- 4
Available from ASTM International Headquarters. Order Adjunct No.
ADJF2508. Original adjunct produced in 2011.
The sole source of supply of the apparatus known to the committee at this time
is Gallade Chemical, Santa Ana, CA. If you are aware of alternative suppliers,
Powers, C. M., Blanchette, M. G., Brault, J. R., Flynn, J., and Siegmund, G. P., please provide this information to ASTM International Headquarters. Your com-
“Validation of Walkway Tribometers: Establishing a Reference Standard,” Journal ments will receive careful consideration at a meeting of the responsible technical
of Forensic Sciences, Vol. 55, No. 2, March 2010, pp. 366–370. committee, which you may attend.
F2508 − 11
7.1.4 RS D—Ceramic whose surface beneath the test foot is area of each of the four reference surfaces that have been
covered with a continuous film of distilled water. prepared in accordance with 8.2. Of the 40 tests, perform 10 in
each of 4 orthogonal directions, that is, at 0, 90, 180, and 270°
7.2 Each RS shall be permanently marked to designate its
relative to an arbitrarily defined direction on the reference
reference class (that is, “A”, “B”, “C”, “D”).
surface. Record the results of all tests as specified in Section
7.3 Reference surfaces shall be stored in a manner that
10.
prevents deformation and contamination.
9. Analysis of Results and Walkway Tribometer
7.4 Reference surfaces should not be used for validation or
Validation
calibration testing after 5 years from date of purchase.
9.1 For the 40 tests on each reference surface, calculate the
8. Procedure ¯
mean ~X!, standard deviation (SD), standard error (SE)ofthe
8.1 Environment—The validation and calibration test shall mean, and 95th percentile confidence interval (CI) for the
walkway tribometer test results for each reference surface
be performed at a humidity level of 50 6 5 % and a
temperature range of 23 6 2°C (73.4 6 3.6°F) (derived from using Eq 1 through Eq 4, respectively:
Practice D1349).
n
¯
X 5 x (1)
~ !
( i
8.2 Reference Surface Preparation—The reference surface
n
i51
shall be free from visible dents, cracks, voids, or other
where:
significant blemishes.
n = number of measurements (40), and
8.2.1 Cleaning:
x = test result
i
8.2.1.1 No surface treatment except as specified in this
section is permitted.
n
8.2.1.2 Prepare a 0.05 % by volume solution of liquid
SD 5 · x 2 xH (2)
Π~ !
( i
n 2 1
i51
sodium lauryl sulfate in distilled water (that is, 250 µL of
SD
sodium lauryl sulfate per 500 mL of distilled water).
SE 5 (3)
8.2.1.3 Dip a clean soft-bristled nylon brush in the cleaning
=n
solution and gently scrub in a circular pattern the entire
¯ ¯ ¯
95th percentile CI 5 X6~1.96 3SE! 5 X 2 ~1.96 3SE! to X1~1.96
reference surface for a minimum of 10 s. Reapply the cleaning
3SE! (4)
solution and repeat the minimum 10-s scrubbing two times.
8.2.1.4 Rinse the surface thoroughly with distilled water,
9.2 A valid walkway tribometer must properly rank the
ensuring that no visible suds or soap residues remain.
friction between the test foot and reference surfaces and
8.2.1.5 Dry the surface with dry and oil-free compressed air
provide a statistically unique slip resistance measure for each
or air dry if compressed air is not available. The reference
surface. A valid walkway tribometer model shall satisfy the
surface shall exhibit no visible moisture film or droplets.
following two compliance criteria:
8.2.1.6 Prepare an ethanol solution containing equal parts
9.2.1 Rank Order—The rank order of the mean walkway
denatured ethanol in distilled water.
tribometer results for each reference surface shall be the same
8.2.1.7 Dip a clean soft-bristled nylon brush, different from
as shown in Appendix X1.
thatusedin8.2.1.3,intheethanolsolutionandgentlyscrubthe
9.2.2 Differentiation—Using the mean and standard
reference surface for 10 s.
deviation, paired t-tests as described in Appendix X2 shall
8.2.1.8 Dry the reference surface with dry and oil-free
produce significantly different results (p < 0.05) for all adja-
compressed air or air dry if compressed air is not available.
cently ranked reference surfaces (that is, between RSAand RS
Any visible contamination remaining after this step will
B, RS B and RS C, and RS C and RS D).
disqualify the reference surface for use.
9.3 Failure to meet the two validation criteria shall be
8.2.1.9 Ensure that handling of the reference surface does
considered an unsatisfactory result. The supplier’s guidelines
not introduce contaminants to the surfaces, including exposing
fortroubleshootingshallbefollowed,andthewalkwaytribom-
the surfaces to contact of human skin.
eter validation repeated. If the results are still not satisfactory,
8.2.1.10 The cleaning procedure should be performed be-
the walkway tribometer fails the validation.
fore each testing session.
8.3 Reference Surface Mounting—Mount the reference sur-
10. Walkway Tribometer Validation Report
face onto a flat and rigid substrate that prevents movement of
10.1 The report shall include information about the walk-
the reference surface parallel to the test plane of the walkway
way tribometer, test foot, referenc
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