Slip Resistance Testing Standards in 2014
Updated May 29, 2014
Sotter Engineering Corporation, Mission Viejo, CA USA
At present the BOT-3000E, modern British pendulum tester, and Tortus are the most useful and reliable floor friction testers to aid in accident prevention. Each has its own appropriate safety standard(s), e.g. 0.42, 36, or 0.50 for a level floor. The information below discusses these slip resistance test instruments and slip test safety standards as well as some others that have been used. Safety Direct America can run slip resistance tests both in the lab or at your site with these instruments (and other test methods upon request), and can also sell you your own slip resistance test instruments.
Testing Standards and Safety Criteria
For slip resistance testing wet or dry
ANSI B101.1, B101.3, and A137.1 are essentially for use of the BOT-3000E digital tribometer. This device is not patented. It is presently made in the USA by a single manufacturer. The BOT-3000E and the corresponding ANSI standards are for wet testing of floors using hard rubber sliders (test feet). ANSI B101.1 measures static friction, which should not be used on its own for assessing anti-slip safety. ANSI B101.3 measures dynamic friction at a lower speed than the modern pendulum. The ANSI dynamic method is sometimes used, without water, to assess dry friction. Leather and other test foot materials are also available for this instrument.
The BOT-3000E performs a test without human input except for setup and the pressing of an electronic button. The instrument includes many features that help in validating a test as to time, date of last calibration by the manufacturer, date and time of last verification by the user, date and time and location number of test run as well as test foot (slider) used, age of and number of runs on that test foot, etc. These features help establish courtroom credibility. See a video demonstration of the BOT-3000E.
The safety standards ANSI specifies for a level floor using the B101.3 dynamic test method is a “high slip resistance” minimum dynamic coefficient of friction (DCOF) of 0.43 and a “low slip resistance” minimum DCOF of 0.30. When DCOF is assessed for a floor or sample, it is probably not necessary to assess SCOF. The Tile Council of North America and the Concrete Polishing Association of America both specify that their members use the BOT-3000E to do a DCOF test only; they don’t even mention SCOF. (Static friction is applicable to a pedestrian who is standing still. An anti-slip floor or slip resistant floor will be anti-slip for someone who is in motion moving across the floor. Static coefficient of friction slip testing is therefore irrelevant.) Both the BOT-3000E and the Tortus (see below) are capable of making significantly more slip tests per hour than the pendulum.
The 2012 International Building Code states that ceramic tile shall conform to the requirements of ANSI A137.1, the current version
of which (September 2012) says that testing shall conform to a BOT-3000
dynamic coefficient of friction test. ANSI A137.1 states that tile
expected to be walked on wet indoors shall have a minimum DCOF of 0.42.
It does not provide a minimum DCOF for outdoor areas or ramps. However,
the test method also states that this modified B101.3 test "can provide a
useful comparison of tile surfaces, but it does not predict the
likelihood a person will or will not slip on a tile surface." The
official ANSI B101.3 test method, and its safety recommendations, are
based on actual slip and fall research in a laboratory under controlled conditions using numerous human subjects. The modified test outlined in
ANSI A137.1 apparently is not.
The ASTM E303 slip resistance test standard defines the British pendulum tester that is now a national standard for pedestrian floor slip resistance in 49 nations on five continents and has been endorsed by Ceramic Tile Institute of America since 2001. It is the most widely used pedestrian slip resistance test method worldwide. The most common safety standard for a level floor is a minimum Pendulum Test Value (PTV) of 36. The pendulum is the basis of the Sustainable Slip Resistance standard that has been specified by McDonalds Restaurants since 2006. Here is a video demo of the modern pendulum slip resistance tester.
hard and soft rubbers are specified for the pendulum, with soft rubber
being applied primarily to barefoot situations such as showers, bathroom
floors, and swimming pool decks.
Test results are usually
quoted as Pendulum Test Values to avoid the confusion that results when
different devices are used to give different values of coefficient of
Australia HB 197:1999 gives detailed recommendations of minimum wet
Pendulum Test Values for many different situations: e.g. external ramps,
54; external walkways and pedestrian crossings, 45; shopping center
food courts, 35; and elevator lobbies above external entry level may be
25 or less. There are also barefoot area recommendations based on
pendulum tests with a soft rubber slider. The Australian
recommendations, published in 1999, are the world’s most detailed and
sophisticated standards for pedestrian wet slip resistance. They have also been used by cruise ship companies and others outside of Australia.
SlipAlert (left) is a roller-coaster type tribometer that is designed to mimic the readings of the modern pendulum. It has been used for field testing, but is of limited utility in laboratory testing because it requires a long path length of flooring. Click here to see a SlipAlert Video Demonstration
The Sigler Pendulum Tester is an older version of the pendulum tester. The Sigler was invented in the mid-20th century by Percy Sigler of the U.S. National Bureau of Standards (now NIST). British workers modified Sigler’s design to produce the modern pendulum (called the TRRL pendulum tester in the UK), which is for that reason sometimes known in the USA as the “British Pendulum.” The Sigler pendulum is rarely used now because the modern pendulum exists. The Sigler is no longer commercially available, but a few survive.
The Tortus digital tribometer slip resistance test method is based on a proprietary or patented device, which makes it ineligible to become an ASTM standard. The Tortus has been endorsed as a secondary standard by Ceramic Tile Institute of America (CTIOA) since 2001, with the pendulum being the primary standard. The advantage of the Tortus, compared to the pendulum, is that it can perform many slip tests in a short period of time, dry and wet, using both hard and soft rubbers. CTIOA has endorsed a minimum dynamic coefficient of friction for level floors of 0.50 using the Tortus slip resistance test method. Tortus video demonstration
former ASTM F1677 applies to the Brungraber Mark II (also known as
Portable Inclinable Articulated Strut Tribometer or PIAST) test device. ASTM
withdrew this standard in 2006, with no replacement. (It is still
available from ASTM as a withdrawn or historical standard.) The reasons for
withdrawal included poor precision in interlaboratory studies, which made it
impossible to present a reasonable precision statement as required by ASTM.
The former ASTM F 1679 applied to the English XL Variable Incidence Tribometer (VIT), which according to its inventor William English was designed primarily for wet testing. ASTM also withdrew this standard in 2006 with no replacement. Again, the reasons included poor precision, which made it impossible to present an acceptable and reasonable precision statement as required by ASTM.
The English XL’s actuating valve pressurizes the actuating cylinder and drives the test foot onto the surface being tested. The ASTM slip resistance test procedure required the operator to “fully depress the actuating valve for approximately 1/2 second”. This valve is sensitive to the amount of force or speed used by the operator to depress it (no doubt a part of the precision problem), which raises the possibility that the operator can unwittingly (or wittingly) influence the result according to his or her preconceived notion of whether the floor is slippery or non-slip.
English XL users often cite that their instrument has passed the ASTM F2508-13 standard called the "Standard Practice for Validation, Calibration, and Certification of Walkway Tribometers Using Reference Surfaces". Although it is necessary for a tribometer to pass this test, it is not sufficient in validating a scientific slip test instrument. This test is often conducted and interpreted by people who have a vested interest in their tribometer having passed the test, and it should not be solely relied upon in deciding whether a slip tester is trustworthy in predicting human traction. An internationally accepted, reliable slip test device will have been found to correlate well with Variable-Angle ramp tests of human traction, have an official (not withdrawn) test method, and be able to provide a reasonable precision statement as required by all official standard-creating agencies.
Usefulness of dry slip resistance testing
Dry slip testing can also be useful with or without wet testing. There are several reasons: (1) dry tests followed immediately by wet tests on the same floor can help demonstrate that the slip resistance test method is capable of measuring both high and low values on the subject flooring; (2) a floor may be dry and appear clean, but be slippery due to a thin film of contaminant, for instance grease in or near a restaurant kitchen or parking structure; (3) dry data can help diagnose problems such as furniture polish overspray, inadequate maintenance, airborne cooking fat that settles to the floor overnight, etc.; (4) a rare small spill on a normally dry floor might have occurred too recently for the defendant reasonably to have discovered it and cleaned it up; and (5) many claims of slips and falls are made that involve dry floors. The actual cause of the slip and fall might be footwear, substance abuse, illness, or many other factors unrelated to the floor. Dry testing — particularly before the alleged accident and on a periodic monitoring basis (traction auditing) — can help establish that the floor was safe (or anti-slip) when dry.
For dry slip resistance testing only
ASTM F609 applies to the Horizontal Pull Slipmeter (HPS), which was an early electrically-operated dragsled meter, and does not permit wet slip testing. The HPS is no longer commercially available. The method applies only to the HPS and not to any other device.
ASTM F1678 has to do with the Portable Articulated Strut Tribometer (PAST) which is also known as the Brungraber Mark I. It is a static slip tester (essentially a portable version of the James Machine — see below) and because it suffers from a stiction problem it is not useful for wet testing. ASTM withdrew the standard in 2005.ASTM C1028-07 for the Horizontal Pull Dynamometer has now officially been withdrawn as a test method and was intended for quality assurance testing of ceramic tile in and out of the factory. It is a 50-pound drag sled that is pulled by a hand-held force meter (dynamometer), and the coefficient of friction (COF) is calculated from the horizontal and vertical forces. This method is not capable of valid pedestrian safety testing under wet conditions. It was once cited by the U.S. Department of Justice Access Board as a potential test method for compliance with the Americans with Disabilities Act (ADA). The Access Board later withdrew this citation, and now provides no suggested test method or safety standard. Please see www.C1028.info for extensive detail and letters of confirmation from the Access Board.
It is reported that ASTM will not renew method C1028 when it comes up for re-approval in 2014, which will doom it to a quiet death after a specified number of years. In ANSI A137.1, the method has been replaced by a test method similar to ANSI B101.3, the BOT-3000 dynamic coefficient of friction slip resistance test, and the safety standard for a level indoor floor is a minimum DCOF of 0.42. This is now part of the International Building Code.
ASTM D2047 is the basis of the testing of floor “waxes” (floor finishes) for slip resistance under laboratory conditions. It involves the James Machine with a leather friction pad, and specifies that all testing must be performed dry. It is a laboratory machine that tests flooring samples and due to its design is not usable on an actual floor. Leather is not suitable for wet slip testing, as its properties change unpredictably and permanently when it becomes wet.
UL410 is an Underwriters
Laboratories (UL) standard. It provides for rating of various materials and
surfaces as “slip resistant.” Materials or coatings may be listed by UL as slip-resistant
if they achieve an index of 0.50 or higher on a James Machine with a
three-inch-square leather pad. Again, the James Machine is measuring static
COF, which is the measure of how slippery a floor is when someone is standing
still on it. This is irrelevant to measuring pedestrian walking floor slip
resistance. Because the test method uses a dry leather pad, it gives lower COF results than if a Neolite or rubber pad were used. Therefore the 0.50 safety criterion is not applicable to friction tests of any kind in which a non-leather pad is used. Unfortunately it has often been applied in this way, indicating that the floor complies with a safety standard when in fact it does not.
The Technical Products Model 80 is a static slip tester as well and therefore is not suitable for wet testing to assess anti-slip pedestrian safety.
The American Slip Meter ASM 725 and 825A are also static friction testers, and therefore not suitable for wet testing to assess pedestrian safety. Slip testers such as these can, however, be somewhat useful in determining whether floor maintenance practices are affecting slip resistance over time by using it as a regular monitoring device on dry floors. Note that despite the similarity of the abbreviations, “ASM” is not related to ASTM and the ASM 725/825A test method is not an ASTM standard.
The Bottom Line for the Property Owner
Those who suffer from slip-and-fall accidents are the accident victims, their family members, and the property owners/managers who are often involuntarily the cause of the accident and must pay damages — either directly or through increased insurance premiums and additional policies written. Many other parties benefit financially from these accidents or sale of the slippery flooring that often causes them: flooring vendors, hospitals, physicians, physical therapists, lawyers, expert witnesses, and (through increased premiums) property insurers. Having a valid method of assessing floor safety would therefore seem to be of most immediate value to property owners/managers.
The United States OSHA has long recommended a minimum coefficient of friction (COF) of 0.50 for workplace safety without specifying how the COF is to be determined. This unfortunately is counterproductive. Different slip resistance test methods give different results, particularly under wet conditions. Thus the same floor could have coefficients of friction of 0.4, 0.5, 0.6, or 0.7 (or anywhere in between) depending entirely on what test method was used. The OSHA recommendation is therefore meaningless, but has caused confusion for many years.
The slip testers that are valid for the appropriate purposes today are
BOT-3000E for cost-effective, rapid and automatically
documented wet testing, both static and dynamic, with various available
test foot materials
Pendulum Tester for dynamic testing wet and dry with hard and/or soft rubber sliders, outdoor area testing, barefoot area testing, Sustainable Slip Resistance Testing, and application of long-established detailed situation-specific standards (swimming pool deck, outdoor ramp, etc.)
Tortus for testing where pedestrians are not likely to be running, and where numerous wet and dry tests are needed with hard and/or soft rubber sliders
No one of these slip resistance testers is capable of doing all the tasks that might be needed. However, the three slip test devices listed above allow the user ample capability for prevention and analysis of slip and fall accidents in almost any situation.
We here at Safety Direct America can slip test your flooring in our lab or on site, or sell you your own slip resistance tester. Feel free to contact us with any questions. Our knowledge and experience in the field of floor slip resistance testing is unmatched in the Americas.