Winter 2001-2002
It has been eight years of hard work and determination to complete ANSI/ASSE A1264.2 Standard for Provision of Slip Resistance on Walking/Working Surfaces, there were times when I thought this standard was just a pipe dream. However, due process does reign after all, and now America's walkways will finally have a standard that addresses safety issues that have never before been codified in voluntary consensus standards, government standards or private standards.
There has been a lot of interest in the promulgation of this standard by OSHA, ASTM, Building Code Administrators, the flooring industry, the footwear industry, and the safety profession. As an accredited standard developer, ASSE was approved to act as secretariat for the development of the standard. Many regional model building codes, OSHA regulations, and other ANSI Standards use the term "slip resistance." The perceived need for this standard was to further define the term "slip resistance," and to set forth common and accepted practices for providing reasonably safe walking/working surfaces. A1264.2 has taken a step in addressing this need and formalizing a minimum consensus standard that would allow industry to provide safer workplaces. ASSE owns the copyright on the standard, and it is currently available from ASSE for a very reasonable price ($38 to members). This standard should be in the library of every risk manager, safety director, property manager and corporation.
I think it is important to convey why a slip resistance guideline of 0.50 was selected. The ANSI A1264.2 subcommittee knew from the beginning of the project that the establishment of a slip resistance guideline would create controversy, opposition, and criticism from various factions within industry. The selection of a guideline was something all members of the committee believed to be of significant importance from the very inception of the project. The following was jointly written by several members of the A1264.2 subcommittee during the course of the project.
History and Background
During his important pioneer work at the National Bureau of Standards (NBS) in the WW II era, Percy Sigler observed that dry surfaces are not slippery, and he set about to develop a slipmeter that could validly measure available traction on lubricated floors. Despite his very respectable studies many tribometric devices have been subsequently invented, patented and marketed which cannot meter wet surfaces because of the sticktion phenomenon, which causes instruments with a residence time (where the horizontal and vertical forces are not applied simultaneously) to give artificially high readings on wet surfaces so as to be misleading.
In the current decade slipmeters operating at velocities commensurate with those encountered in ambulation (and which can avoid sticktion by avoiding residence time) have become available. For these devices to be useful in determining compliance with performance?based guidelines, a slip index guideline that affords a reasonable measure of safety must be specified. To discuss what that number should be, we must look at historical investigations and guidelines.
Underwriters Laboratories
Sidney James, working at Underwriters' Laboratories, modified the original dynamic friction tester Hunter had developed at NBS, resulting in the massive static coefficient of friction (SCOF) measuring machine that bears his name to this day. It became the standard for rating polish-coated floor surfaces.
Mr. James is said to have conducted experiments by walking on polished surfaces that were thought to be adequately slip resistant, taking increasingly long strides until his heel slipped. By performing the trigonometric calculations recognized at NBS and in physics texts as the formula for static coefficient of friction (as measured by the articulated strut principle), he came up with the 0.5 SCOF as the threshold of safety for normal ambulation.
In 1992 Underwriters Laboratory issued UL 410 "Standard for Slip Resistance of Floor Surface Materials", the performance portion of the standard requires an average SCOF of 0.5, as measured by the James Machine, for walkway materials.
The recommendations put forth by this committee have been an attempt to be fair to the floor industry as well as workers, by prescribing the use of Neolite as a test pad. Although the recommended testers cannot be correlated to the James Machine, committee members, through investigations and studies, feel confident that the 0.5 criterion chosen can be achieved by manufacturers of flooring products. The committee members are also confident that workers will be afforded a safer walking /working surface given this criterion.
American Society for Testing and Materials (ASTM) D?21 Committee on Floor Polish
This longstanding group has followed Sidney James' doctrine religiously and continues to support his 0.5 threshold of safety in connection with D?2047. D-2047 is the "Test Method for Static Coefficient of Friction of Polish-Coated Surfaces as Measured by the James Machine." This test method prescribes a minimum criterion of 0.5 SCOF as the threshold of safety, and has done so since 1974. However, no one has been able to produce research or hard data showing the basis for the 0.5 criterion put forth in this standard.
ASTM D-2047 specifies leather as the sensor material to be used. The committee, in choosing Neolite (which is generally more slip resistant than leather), believes that it has taken a conservative approach by using a material less prone to slip, on most floor surfaces and under most conditions, than leather. The committee believes this will serve both industry and workers well.
OSHA
In the April 10, 1990, Federal Register, Vol. 55, No. 69, p 13408, 29 CFR, Part 1910, "Walking and Working Surfaces and Personal Protective Equipment (Fall Protection Systems); Notice of Proposed Rulemaking", a value of 0.5 was recommended in workplaces.
These proposed amendments to the 1910 workplace safety regulations were never incorporated into the CFR, but are still on the books as a pending proposal. Many knowledgeable professionals agree that the 0.5 value could be legally enforced under the "General Duty Clause" of the OSHAct. A major flaw with the proposed rules was that they did not specify a test method, to comply with the intent of the proposed rules. OSHA generally looks for guidance from ANSI standards, and with that in mind the committee has set forth specific recommendations with regard to methods, procedures, and materials to allow any employer to evaluate a walking/working surface.
Architectural and Transportation Barriers Compliance Board (Access Board)
At the ASTM F?13 symposium on Slips, Trips, Stumbles and Falls in Denver on October 23, 1989, Dr. Frank Buczek presented a paper describing work that he and his colleagues had performed to measure required traction for various individuals having mobility impairments in locomotion. Their findings were accepted by the Architectural and Transportation Barriers Compliance Board as the basis for the thresholds of safety they subsequently specified for public access routes.
The values chosen by the ATBCB were published as recommendations and were considered unenforceable, as they were part of the appendix section of the Americans with Disabilities Act (ADA). It was also technically unenforceable due to the fact that no test method was established. These recommendations are reportedly will be withdrawn.
Values published in the Federal Register on July 26, 1991 as the Americans with Disabilities Act Accessibility Guidelines (ADAAG) called for a slip index of .60 on level walkways and .80 for ramps up to a slope of 1:12. These values are even more stringent than the 0.5 slip-resistance value suggested by the ANSI A1264.2 Committee.
Case Law and Expert Opinion
For the past half century court precedent has allowed that 0.5 is the recognized threshold of safety, without serious challenge to this number.
Although different spokesmen for pedestrian safety have disagreed on how high (or low) the threshold should be, most seem to be in approximate agreement. For example, Dr. Robert Brungraber, who has been recognized in print as the world's preeminent expert on pedestrian slip resistance has often averred in F?13 Committee meetings and elsewhere that 0.5 should be specified as the threshold of safety.
Additional Discussion
The subject of minimal traction demand for safe ambulation has been well studied over the past 60 years or so. From the start a slip index of 0.5 has been presented as a minimal value for safe walking, allowing a small margin of safety.
There has been no serious objection to the 0.5 threshold when it is applied to the safety of dry walking surfaces. But there has been heated controversy concerning the threshold of safety on contaminated surfaces, although a pedestrian's traction requirement is always the same in normal ambulation. However, there has been no significant research published in the scientific literature in modern times to seriously challenge the 0.5 threshold.
Since our consideration here (in ANSI 1264.2) is primarily for workplace safety, and since many kinds of lubricating contaminants challenge the safety of employee footing in industrial processes, we should concern ourselves primarily with slip indices of contaminated surfaces. Further, since 0.5 is a largely unchallenged value for the general public on dry surfaces, the same traction value would afford reasonable safety for workers in industrial environments for many workplace activities on level surfaces where lubricating contaminants are present. The longstanding 0.5 is adequate for normal ambulation by normal people, with some margin of safety.
Concluding Remarks
The establishment of 0.5 for general exposure would enhance workplace safety significantly. However, industry professionals would be prudent to evaluate specific circumstances where a higher threshold may be needed, such as in applications where greater physical exertion would dictate higher available traction. No guideline can contemplate every contingency, but this standard should specify a minimal level of performance that is widely supported by the present body of scientific knowledge. A minimum slip index of 0.5 would be the least controversial number to choose for workplace exposures in our context, and will produce significant benefit to the workplace.
The fact that falls account for a significant amount of workplace injuries and literally millions of dollars of loss, has created a concern amongst the experts to start somewhere. This committee feels this is a new start in a continuum of progress toward making work environments safer.
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