There are a number of floor slip test methods established by standards-setting organizations that assess pedestrian slip resistance. Here we’ll review the most widely known and current ones. They are distinguished by the devices used in the testing. Terms such as DCOF rating, coefficient of friction, slip coefficient, slip resistance rating, and friction coefficient all refer to the same thing – a scientific measure of the slip resistance of a flooring surface for pedestrians.
The Brungraber Mark II and English XL tribometers briefly had standards published by the American Society for Testing and Materials (ASTM). They never met the ASTM requirements for precision, and the ASTM withdrew them soon after publishing with no replacements. A more recent version of the Mark II, the Mark IIIB, has never been the subject of an official published or peer-reviewed standard. These devices seem to be used now mainly by “expert witnesses” who wish to somehow make a case for their client. The gadgets do not have applicable official standards in other countries either, and thus are not backed by any standards-setting organization anywhere in the world.
The BOT-3000E slip test device has standards issued by the American National Standards Institute (ANSI). The current one favored by the manufacturer of the instrument, and by Tile Council of North America (TCNA), is ANSI A326.3. Previous standards (still being sold) for the device include B101.1, B101.3, and A137.1. ANSI A326.3, it should be noted, is only intended for use on indoor, level floors, and does not yet have a standard using a softer rubber that would be helpful for measuring barefoot areas.
The most widely accepted test method is known as the “British” Pendulum tester, which was invented by the U.S. National Bureau of Standards and has been in constant use for pedestrian traction since 1971. It is the subject of ASTM Standard E303, has been endorsed by Ceramic Tile Institute of America since 2001, and was validated against human traction testing by the University of Southern California Medical Center’s Department of Biokinesiology & Physical Therapy.
The pendulum has for years been established as an official national standard for pedestrian traction in at least 50 nations including (but not limited to) Australia, Belgium, Czech Republic, Denmark, Dubai, Egypt, France, Germany, Greece, Hungary, Iceland, Ireland, Israel, Italy, Luxembourg, Netherlands, New Zealand, Norway, Poland, Portugal, Romania, Russia, Singapore, Spain, Sweden, Switzerland, Tunisia, Turkey, Ukraine, the United Kingdom, and the United States of America.
An advantage of the pendulum is that its safety standard — the minimum wet Pendulum Test Value that is considered safe — is not “one size fits all”, but has some 40 long-standing situation-specific minimums, for example for external level surfaces, external ramps (mild and steep), commercial kitchens, swimming pool decks, external stairways, hospital bathrooms, etc. What is safe for a 10th-floor indoor elevator lobby may not be safe for a communal shower room or pool deck. This is floor slip resistance testing for the 21st century.
The rubber the pendulum uses to simulate shoe heels or bare feet can be hard or soft, with appropriate safety standards for each. Hard rubber is obviously not a good medium for representing bare feet. Soft, flexible media (like skin) can flow around the micro-rough features of a surface that give it good wet slip resistance when hard media (standard shoe soles) are concerned. Therefore a swimming pool deck, for instance, should be tested with soft rubber as well as a hard rubber to see what the real-world slip resistance will be for people wearing shoes as well as people walking barefoot.
The pendulum is also used in the test for Sustainable Slip Resistance established by McDonalds Restaurants after years of research. This test assess how durable wet slip resistance of flooring is likely to be after many pedestrians have walked it. Another use of the pendulum is for dry testing of gym floors used for basketball, volleyball, etc.
It is extremely important to consider precision when deciding which slip resistance test instruments offer valid results for assessing real-world pedestrian safety. There are instruments that have been developed only to aid in legal defense, and these instruments allow the user to get whatever answer they are being paid to get for the lawyer who has hired the “expert.” Valid instruments will have international acceptance, have published, peer-reviewed official test standards, and will have been shown to have acceptable precision in interlaboratory studies. The BOT-3000E and pendulum slip resistance tester meet these criteria, whereas the Brungraber Mark IIIB and English XL devices do not. Want to win a lawsuit at any cost? Hire someone with a Brungraber Mark IIIB. The device has no published standard anywhere on earth and can get you the result you need to put together an unscrupulous case. Want to know if your floor is actually slippery or not using real science? Use a device with an official published standard for its use, such as the BOT-3000E or the pendulum skid tester.