View English XL and Mark IIIB Floor Friction Data with Suspicion

A recent paper published by Siegmund et al. called “Quantifying the uncertainty in tribometer measurements on walkway surfacesstates that data from the English XL and Brungraber Slip-Test Mark IIIB are “less accurate than they appear.” This is in part because the user is “a key component to the system,” influencing the numerical outcome of a test. “Every operator gets a different result.” This helps explain why these “instruments” have been primarily used by expert slip and fall “liars for hire” for decades.

English XL (VIT)

English XL “Tribometer”

The Experiment:
In this study, the researchers asked four individuals to test the slipperiness of four floor samples using two types of tribometers: the Brungraber Slip-Test Mark IIIB and the English XL. Their goal was to understand how accurate these devices were and what factors might affect their measurements. (The Brungraber and/or Slip-Test Mark I, Mark II, Mark III, Mark IIIB and other versions of the instrument shown below all seem to be very similar, and seem to all get miraculous readings for their users when used in slip and fall lawsuits.)

Brungraber Mark II and Mark IIIB Tribometers

Brungraber Mark II and Slip-Test Mark IIIB

The Not-So-Startling Findings:
What they discovered was not at all surprising to anyone who has slipped and been injured on a floor, only later to find that one of these “expert slip and fall court liars” have reported that the floor wasn’t slippery at all (and got paid lots of money by a slick lawyer to produce the report saying so). The research paper, written mostly by people who have made their living testifying in slip and fall cases for big money, revealed that the results obtained from these tribometers were not very reliable.

In fact, a significant portion (around 51% to 82%) of the differences in measurements were due to factors other than the person conducting the test. These factors included the specific tribometer used and how well the person and the machine worked together. This means that the measurements obtained from these two tribometers are not as precise as should be necessary to be allowed in court. Even if the same person tests the same floor multiple times, the results can vary due to these other factors.

Why It Matters:
Why should we be concerned about the uncertainty reported in this research? Well, when we use tribometers to assess the safety of floors, we want to make sure our results are accurate and based on internationally peer-reviewed real-world slip and fall research. If we ignore the uncertainty and unreliability of these two instruments, we might mistakenly believe a floor is safe when it’s actually slippery.

That could lead to accidents and injuries to innocent pedestrians, which we definitely want to avoid! But it also leads to expert court liars being able to make fantastic living lying in American courtrooms, saying that slippery floors aren’t slippery, and vice versa. Readings from the English XL and Mark IIIB can be used to say polished floors and floors that have had multiple serious slip injuries occur on them aren’t slippery at all, and creating reports for the wealthy owner of the property saying so can make a “slip and fall expert witness” very popular with defense attorneys indeed!

The test methods for these two instruments were withdrawn by the ASTM and rejected by OSHA almost 20 years ago now, and this recent research helps explain why: the results from these tribometers are too unreliable. With this amount of uncertainty, it appears that it is not prudent to use readings from these instruments to draw scientific conclusions, or to trust conclusions by others based on the English XL or Brungraber Mark IIIB.

Ensuring Safety:
In conclusion, this research paper highlights the unreliability of the results obtained from these tribometers. The findings remind us to be skeptical of the accuracy of these devices and to consider the uncertainties associated with their measurements. By using instruments that have international acceptance, published test methods in multiple nations, and decades or research finding the instrument to be reliable in assessing safety such as the pendulum dynamic coefficient of friction (DCOF) tester, we can ensure that the floors we walk on are as safe as possible.


ASTM E303-22 was just updated and re-published in 2022 (the first version was originally published by the ASTM in 1993) to reflect the pendulum floor safety standards used across the European Union, the United Kingdom, Australia, New Zealand, and dozens of other nations around the world. Remember, it’s important to question and verify the reliability of the tools we use to ensure a secure environment for all! The pendulum tester has decades of published research saying it’s a reliable and useful tool. All evidence about the English XL and Brungraber Mark IIIB points towards the fact that these tribometers are about as reliable as a paper bathing suit.

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