Q.: What's a reasonable coefficient of friction that will help to prevent slip-and-fall accidents on concrete floors? Is there a standard method for measuring the coefficient?
A: At this point, there's no answer for either of your questions. The executive summary for a 1996 National Institute of Standards workshop on evolution of slip-resistance standards cited widespread confusion about slip-resistance measurements, standards and acceptable criteria. The workshop participants represented a cross-section of interested parties, including manufacturers of flooring materials, representatives of federal agencies concerned with building safety and members of American Concrete Institute, American National Standards Institute and ASTM committees independently developing slip-resistance and related standards.At the end of the final session, those present unanimously agreed on the following:
- There is a need for improved standard test methods and performance criteria for slip resistance of floors.
- An independent, authoritative committee should be established to recommend actions needed to reduce the number of slips and falls and the seriousness of the injuries caused. Steps to be taken by the committee should include a critical review of existing information on the causes of and ways of preventing slips and falls, and an assessment of the scientific basis for existing slip-resistance measurements and their relationship to actual slips and falls.
Our interpretation of these conclusions: No standard test for slip resistance and no criterion for acceptable values of slip resistance will be available any time soon.
Geoffrey Frohnsdorff and Jonathan Martin, "Seeking Validation and Consensus on Slip-Resistance Measurements and Standards," NISTIR 5988, National Institute of Standards and Technology, Gaithersburg, Md., 1996.
While I agree that confusion exists in the industry, I believe an answer is currently available. As an engineer with Construction Technology Laboratories, I am involved in testing the slip resistance of flooring surfaces. CTL provides this service as a litigation tool as well as a test for manufacturers. With regard to the current industry standard, I typically write in my test reports that the Occupational Safety and Health Administration recommends that walking surfaces have a static coefficient of friction of 0.5. However, as specified by the Americans With Disabilities Act, the Architectural and Transportation Barriers Compliance Board sponsored research concluding that a higher coefficient of friction is needed by pedestrians with disabilities. The study recommends a static coefficient of friction of 0.6 for accessible routes and 0.8 for ramps. In my experience, the most effective test procedure for evaluating the static coefficient of friction for footwear materials is ASTM F 609, "Standard Test Methods for Static Slip Resistance of Footwear Sole, Heel, or Related Materials by Horizontal-Pull Slipmeter." The method measures the coefficient of friction for two common footwear sole materials (leather and neolite rubber) on wet and dry surfaces. For litigation cases, the material from the actual shoe worn in the accident can be used in the test.--Scott M. Tarr Skokie, Ill.