New Study Shows Sotter Engineering to be one of World’s Most Accurate Pendulum Floor Slip Test Labs

A recent global interlaboratory program “Slip Resistance Proficiency Testing — Pendulum Friction Tester,” showed Sotter Engineering Corporation’s Safety Direct America (SDA) floor slip resistance testing laboratory to be one of the world’s most accurate in use of the pendulum skid tester. The pendulum is a national standard for pedestrian floor and tile slip resistance testing in at least 50 nations.

The program, supervised by Carl Strautins of Safe Environments Pty Ltd. in Australia, included 39 dynamic coefficient of friction (DCOF) floor slip test facilities in eight countries throughout North America, Europe, Asia, and Australia and New Zealand.

Each tile slip coefficient laboratory tested identical samples of five surfaces, as shown in Table 1 below. The pink lapping film (PLF) and P400 abrasive paper are reference surfaces widely used in pendulum testing. The tiles were samples that were chosen in part because they had consistent slip resistance from one sample to the next.

The results in Pendulum Test Value, PTV, are shown for both hard rubber (Slider 96) and soft rubber (Slider 55) sliders. A video demonstrating the pendulum tester is available online.

Pendulum DCOF rating values - pendulum slip resistance proficiency test

Table 1. Samples tested in the study; and SDA Z-scores for each sample

In Table 1, Z-scores are a measure of the number of standard deviations that the study participant is from the assigned consensus value of the PTV for a particular sample. For the absolute value of Z-score:

< 2 is considered satisfactory

2-3 is considered a warning signal

> 3 is considered an action level where corrective action is required.

As the Table shows, SDA’s Z-scores were all well within the “Satisfactory” range, having absolute values from 0.21 to 0.75. Twenty of the 39 participating labs — more than half — had one or more Z-scores of 2.0 or higher, outside of the satisfactory range.

Summing the absolute values of the ten Z-scores of the labs that tested all ten surfaces and had only Z-scores of less than 2 indicates that SDA was in the top three of the 39 worldwide floor friction laboratories in terms of accuracy.

Laboratories that want to participate in further pendulum DCOF tester proficiency testing and characterization studies can contact Mr. Strautins at

The pendulum DCOF floor friction tester has been in continuous use for 50 years now in assessing the slip resistance of floors. It is easily the most widely-accepted field floor slip resistance test device in the world today, and is backed by sound scientific research into tens of thousands of real-world slips and falls. If you need to know the slip resistance of your tile or other hard flooring surface, preferably before it is installed, then contact Safety Direct America for a floor slip resistance test right away. Knowing whether or not a flooring sample’s slip resistance is appropriate for its intended use can save lives, help avoid slip and fall lawsuits, and save property owners the hassle and expense of replacing the flooring or applying a remedial solution to slippery floors after they’re installed.

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