ASTM F2508 and the pendulum slip resistance tester

ASTM F2508 is based on a rigorous scientific study of 11 tribometers (or floor slip resistance test devices) that was held at the University of Southern California Medical Center. The peer-reviewed results were published in 2010 in the Journal of Forensic Sciences. Four tiles were tested with the 11 slip test devices, and later a walking experiment was conducted with these same 4 tiles to see which ones caused the greatest amount of slips. The only devices to correctly rank these four tiles were the two pendulum testers, and Brungraber Mark II and Mark IIIB devices.

ASTM F2508 requires the slip test device to rank these four tiles in order of slip resistance now that the answers are already known and have been published. It’s like taking a very basic test with the answers written down on the back of your hand. Now a tribometer can be manipulated to get the correct results once they know the correct results.

This test does not VALIDATE a tribometer at all…it only addresses half of what is necessary for a slip test device to be considered a valid scientific instrument. Not only must an instrument be able to tell the difference between a slippery floor and a more slip resistant one, but it also must have repeatability and reproducibility. In other words, different users must get the same answer on the same tile…or very close to the same answer…when using a particular slip test device.

ASTM F2508 is extremely popular amongst users of instruments that either have NO official test method anywhere in the world, or with users of instruments that have had their test method withdrawn because of their lack of ability to provide the standard publishing agency with a reasonable precision statement. The Brungraber Mark II and English XL are two instruments that very briefly had an ASTM standard, but both of those test methods were withdrawn after it was found that every different user of these instruments can get a completely different answer on the exact same tile samples, making these instruments far from “scientific”. The Mark IIIB has the same reproducibility issue, and therefore does not have an official, peer-reviewed test method anywhere on planet earth. The English XL and the Brungraber Mark III are  two instruments that are widely used by full-time slip and fall expert witnesses who are paid to get the results the lawyer hiring him needs to get to win a lawsuit…so these instruments can be easily manipulated by the user to get the desired result.

The British pendulum device, on the other hand, has an official test method in at least 49 nations, and has been in continuous use for 50 years now. It has acceptable reproducibility and repeatability, and is used to give clients the TRUTH as to what the actual real-world slip risk is for a particular flooring.

The pendulum can and does pass the ASTM F2508 test all the time, every time, but verifying the pendulum on a regular basis uses a much more stringent procedure. The pendulum is verified by a procedure similar to ASTM F2508, but it goes way, WAY further because not only must the pendulum be able to tell the difference between slippery surfaces and slip resistant ones, but it must give the same answer each time these reference surfaces are tested. The zero point, which many tribometers don’t have, is established first. Then float glass is tested, which must have a reading of 7, give or take a couple of points. Then a standard Pavigres tile is tested, which must give a reading of 34, give or take two points. And finally a product known as 3M Pink Polishing paper is tested, and it must have a pendulum test value of 61, give or take a couple of points.

So validating a tribometer using only F2508 is really not validating and verifying it as a valid scientific instrument at all, whereas the pendulum device uses a MUCH more rigorous verification procedure. So don’t be fooled by so-called expert witnesses who say that either the pendulum hasn’t passed F2508, or the pendulum needs to pass it annually. It passed F2508 in the original study it is based upon, it passed it in a subsequent study published in 2013 (“A Study on the Improvement of Validation and Application for Slipmeters using Reference Surfaces” by Kim, Jung-Soo), and you can witnessed it pass this very basic test again by watching the video below.

Slip and fall lawyers and their expert witnesses often use unscrupulous practices and spread misinformation to win lawsuits, whereas we here at Safety Direct America are here for accurate slip risk assessment data – so that architects, insurance companies, tile manufacturers and specifiers can know the truth as to how slippery a particular flooring is…so it can be used in an appropriate area and not be the cause of numerous costly slip and fall accidents and lawsuits. Want to know the truth about your flooring or flooring sample based on 50 years of scientific research? Give us a call or visit us at We’re here to help.

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