In the United States often times static coefficient of friction is used to assess a product’s slip resistance. The problem with this is US building codes and laws require flooring to be slip resistant over its life cycle, not just when it’s installed.
In an article by George Sotter of Sotter Engineering Corporation, he discusses a particular form of measuring slip resistance that is called Sustainable Slip Resistance (SSR). There are many existing methods such as the pendulum tester that has been used successfully since 1971. Regardless of the method used to measure slip resistance, wear and elements such as dirt and dust can render the surface.
This holds true to any public area pedestrians access, including sidewalks. Some cities store electrical machinery underground and they are covered by a sidewalk hatch. A sidewalk hatch should have a high coefficient of friction (slip resistance), whether wet or dry. In most cases sidewalk hatches are exposed to weather and high traffic volumes that can wear certain surfaces and make them more slippery.
The Sustainable Slip Resistance testing consists of an initial wet pendulum test; abrasion, wet for up to several thousand cycles with a standard abrasive pad under a load of 1 kg at 50 cycles per minute’ and another wet pendulum test after abrasion. Both bare feet and standard rubber soles are used for this test.
In the US, some designers look for a coefficient of friction that is 0.60 or higher by ASTM method C 1028. SLIPNOT galvanized steel tested at .93 in dry conditions and .92 in wet. SLIPNOT products are often utilized to decrease liability for property owners, designers and engineers. One product specifically is the sidewalk hatch, when the SLIPNOT coating is applied to a vault lid it creates a safe walking surface for pedestrians. Often times dimpled or diamond plate is used because it is significantly cheaper, however, the raised portions tend to wear very easily and anyone who has walked on a cover that has been there for a couple of years knows how slippery they can be.
It is important to look at all aspects of any slip resistant product, not only static coefficient of friction, but the coefficient of friction when wet and after an abrasion test. These couple of steps can save an owner or designer from the cost of having to replace failing products.
Sotter, George. “2010 International Conference on Fall Prevention and Safety”.
