How do you KNOW if a walkway is too slippery?

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Frequently Asked Questions:

  • Is the Slip-Test Mark II or Mark IIB still available?
    • The Mark II was superseded by the re-engineered Mark IIB; both use a 10 pound weight for actuation (rather than the spring used in the Mark IIIB), but the Mark IIIB is better for most tribometry.  Because of this, and due to lack of demand for the Mark IIB, these are no longer in production.
  • The NFSI floormat test method 101-C, referenced in the NFSI floormat "high-traction" certification process in NFSI B101.6, specifies the use of the Mark II or Mark III tribometer.  What is the relationship between Slip-Test and NFSI in terms of this NFSI standard?
    • Slip-Test has had no relationship with NFSI and does not support the methodology or reliability of their floormat certification process.  The Mark II and Mark III (and Mark IIB / Mark IIIB) tribometer designs require a fairly stiff testfoot material, above approximately Shore 35A durometer.  The tribometer will not work correctly with softer rubber, foam, or textile substrates below Shore 35A that are used on floormats.  It would be necessary to basically disable the normal functionality of the Mark II / III / IIB / IIIB when testing such softer materials - measurements will not be reliable.  
  • There is a lot of information on the internet about the Mark II tribometer and the withdrawn ASTM F1677 standard for it.  What is the relationship between the re-engineered Slip-Test tribometers and the withdrawn F1677?
    • The F1677 Standard Test Method as written described the original Slip-Test Mark II PIAST tribometer produced by Robert Brungraber.  The Mark III tribometer and the re-engineered Mark IIIB and Mark IIB tribometers all operate similarly and can be used per F1677.  The F1677 standard was withdrawn by ASTM in 2006 for two reasons: 
      • The F1677 test method referred to a "proprietary device", which is not allowed by ASTM where "alternatives exist".  But experts know that due to the nature of friction testing and its dependence on the operational characteristics of the tribometer, there are no "alternatives" to the Mark II - not the English XL, not even the Mark III.  These devices are not alternates to each other.  They operate differently and will provide different results on the same surface - this is expectable, and does not diminish their individual capabilities.
      • The ASTM-required precision and bias statement was never published in the F1677 test method.  A precision and bias (P&B) statement is derived from an Interlaboratory Study, involving multiple tribometers and operators, and statistical analysis of the results.  It is widely asserted that the lack of a published P&B statement in F1677 proves a critical deficiency in the performance of the Mark II.  However, numerous Interlaboratory Studies had been conducted using the Mark II,  prior to 2006 - some of these studies are discussed in ANSI/ASSE Technical Report TR-A1264.3-2007, available from  Nevertheless, there is a difference between having a P&B statement and actually getting it published in a standard - procedural and political issues can significantly hamper standards creation. The results of those past Interlaboratory Studies speak for themselves, regardless of whether an associated P&B statement was able to be published in ASTM F1677. 
    • Our re-engineered Slip-Test Mark IIIB tribometers, though operationally identical to the original Mark III designed by Robert Brungraber, use improved materials and manufacturing methods, and provide different results (compared to the originals) on the same walkway surface.  Both the Mark IIIB and the (now out of production) Mark IIB have successfully passed ASTM F2508 Validation - a distinction that few tribometer designs have achieved.  Further, the Mark IIIB has a precision and bias statement as part of its achievement of Certification to ASTM F2508 - see the P&B statement in our Certification Report here!  The report also contains the test method Slip-Test recommends - which significantly differs from ASTM F1677.
  • What is the status of the NBS/NIST-Brungraber Mark I, as used in the ASTM F462 test?
    • Slip-Test does not manufacture, rent, sell, or service Mark I tribometers, which were last sold new in 1993.  Slip-Test offers for purchase full-scale scans of 17 original Mark I manufacturing drawings, circa 1975.

A few of the technical publications that reference Slip-Test tribometers:

  • Chang WR et al.  Development of an objective determination of a slip with a portable inclineable articulated strut slip tester (PIAST). Safety Science 48 (2010), 100–109.
  • McCorry RW et al.  The anatomy of a slip: kinetic and kinematic characteristics of slip and non-slip matched trials. Applied Ergonomics 41 (2010), 41–46.
  • Powers CM et al.  Validation of walkway tribometers: establishing a reference standard. Journal of Forensic Sciences, March 2010, Volume 55, Number 2, 366-370.
  • Leffler JP.  Forensic engineering use of walkway traction testing. Journal of the National Academy of Forensic Engineers, Volume XXVI, No. 1, June 2009, 121-138.
  • Li KW et al.  Evaluation of two models of a slipmeter. Safety Science 47 (2009), 1434–1439.
  • ANSI/ASSE Technical Report TR-A1264.3-2007, Using Variable Angle Tribometers (VAT) for Measurement of the Slip Resistance of Walkway Surfaces. American Society of Safety Engineers, Des Plaines IL, 2007.
  • Li KW et al.  Friction measurements on three commonly used floors on a college campus under dry, wet, and sand-covered conditions. Safety Science 45 (2007), 980–992.
  • Li KW et al.  Relationship between the measured friction coefficients of floors on a horizontal surface and on a 10 degree ramp. International Journal of Industrial Ergonomics 36 (2006), 705-711.
  • Li KW et al.  Slips and Falls - Employee experience and perception of floor slipperiness: a field survey in fast-food restaurants. Professional Safety, September 2006, 34-38.
  • ASTM F1677-05 (Withdrawn) Standard Test Method for Using a Portable Inclineable Articulated Strut Slip Tester (PIAST) ASTM International, West Conshohocken PA, 2005.
  • Li KW et al.  Floor slipperiness measurement: friction coefficient, roughness of floors, and subjective perception under spillage conditions. Safety Science 42 (2004), 547–565.
  • Chang WR et al.  The role of friction in the measurement of slipperiness, Part 2: Survey of friction measurement devices. Ergonomics, 2001, Volume 44, Number 13, 1233–1261.
  • Chang WR, Matz S.  The slip resistance of common footwear materials measured with two slipmeters.  Applied Ergonomics 32 (2001), 549–558.
  • Chang WR.  The effect of surface roughness on the measurement of slip resistance.  International Journal of Industrial Ergonomics 24 (1999), 299-313.


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