Slip Resistance in Safety Footwear

In June of 2018, Work Wear Safety Shoes announced to its footwear vendors that it would no longer sell any product that did not carry at least a coefficient of friction rating of .35 oily/wet proven with tests from an accredited independent lab.

That announcement sent a wave through our vendors since it impacted a lot of the styles we were carrying at the time. Quite frankly, we did not know how to be an expert guide to our Customers and Partners on the safety and wellness of their employees without setting a standard ourselves for our selection. We felt it was irresponsible to sell products that “claimed” slip resistance, but really did not provide the necessary protection in a work environment. So we drew a line.

Unfortunately, it is very easy for a shoe to have the words “slip resistant” printed on the outsole. And the sad part is that it gives a false sense of security to the Safety or EHS Director. They believe they are protecting the employees with these shoes because they have the slip resistant marking on the outsole.
At the same time we announced this new standard for Work Wear Safety Shoes, we also joined the American Society of Testing Materials better known as ASTM. Founded in 1898, the Association of Testing and Materials (ASTM) currently publishes over 12,000 standards at use in 140 countries around the world.We joined the ASTM F30 Committee that deals specifically with setting and establishing standards and testing methods for safety footwear. We wanted to have a voice and part in bringing a standard for slip resistance to safety footwear so our Customers could have confidence in the products they were selecting to keep their employees Safe, Productive and Happy on the job.

While we do have ASTM standards for safety shoes for toe caps, puncture resistance and metatarsal guards, there is not one for slip resistance. At one time, there actually was a slip resistance method. It was ASTM F-1677 which is more commonly known as the Mark II test. However, this testing method was withdrawn by ASTM in 2006 – meaning it’s no longer valid as a standard.

While the Mark II is not a true “standard” anymore, most American brands use this method for the testing of their shoes. And while it has its imperfections, it does help you differentiate between shoes.
The new testing standard we are proposing at the ASTM is ASTM F-2913 – “Standard Test Method for Measuring the Coefficient of Friction for Evaluation of Slip Performance of Footwear and Test Surfaces / Flooring Using a Whole Shoe Tester” – or “Whole Shoe test.” Yes, that is a mouthful to say (and type) but this is how the new standard that is out for approval vote right now will be titled.

In the Whole Shoe test, the footwear sole is brought into contact with a set amount of force for a short period and then moved horizontally at a constant speed. The horizontal frictional force is measured after movement starts and the dynamic coefficient of friction is calculated. This is the coefficient of friction rating mentioned earlier. It is reported as a decimal number such as .35.

It’s possible to measure the coefficient of friction of a shoe, but when we are talking about the wearer keeping traction on the surface while working, we have to think beyond the basic surface and include other hazards that may combine with it. For example, we would concede that many of the shoes with the slip resistant marking on the outsole can provide adequate slip resistance or traction on a dry concrete floor. But the truth is, many employees do not work on a dry concrete floor. We have to consider the other hazards at play like the floor “sweating” and condensation being present or the work environment uses sprays or chemicals. Or consider the kitchen with flour on the floor or the home improvement store with sawdust or the machine shop with oil or metal shavings on the floor. All of these are typical examples of ways the floor surface becomes even more slippery and why this coefficient of friction rating is so important.

This is why we set the Work Wear Safety Shoes standard at .35 oily/wet. A surface that has a mixture of oil and water on it is the most dangerous and the most difficult to retain traction. Keep in mind, we are not referring to “standing” water, but small spills that do not cover the entire surface. It’s logical to conclude that no footwear regardless of its rating would protect someone in standing water.
A few months ago, we had a Safety Director call us about a recordable incident from a slip on the floor. They were upset because the shoes they were providing all had slip resistant on the outsole. How could this happen? They wanted to switch to us as their provider from their current one because they thought their current provider had sold them defective shoes.

“What was the test result of the shoe being worn during the recordable?,” I asked. “What is that?” was the Safety Director’s reply. I then began to explain about testing and the coefficient of friction ratings and what they mean and that it likely was not a defective shoe, but the wrong shoe for the environment. He shared that no one had ever gone through this with him before. But that it all made perfect sense. We completed a full safety and wellness assessment of his environment and then provided them the guidance on what specification they should put into their program.

Truthfully, the lack of education around slip resistance in safety footwear leaves many companies’ programs at a disadvantage. And we are trying to change that.

Now that was a great story for us, but it’s important to remember, that slip resistant footwear and the ratings provided from the test results still do not ensure that the shoe will never slip. What you can count on is the propensity to slip or lose traction based on the rating. For example, a shoe that boasts a test result of .35 dry will not be as safe as one that has a .35 oily/wet result since it takes more traction to stay safe on an oily/wet surface. In many test results, we see a result of .50 dry and a result of .35 oily/wet for the same shoe. So you can see how hard it is to remain traction as the surface becomes more treacherous.
So the higher the result, the higher propensity the shoe’s outsole has to retain traction and grip pon the surface while walking. Think of this this way. I have three elementary-aged daughters who love to play outside. The other day I told them to wear a jacket since it was cold outside. They came out wearing lightweight Gap hoodies. Now, while these hoodies will be better than no jacket, they were not enough to keep them warm in the cold temperatures. And slip resistance on footwear is the same thing. A slip resistant shoe might be good enough in some situations, but not in others. The rule is – the higher the result the better the traction. However, it’s still always possible to slip. Just like it’s still possible for my girls to go outside all bundled up and still get cold. No shoe, no matter how high the rating is guaranteed not to slip. If someone tells you it is, then run.

Another factor to consider is the material the outsole is made of. If it is not durable and wears down quickly, the slip resistance will also diminish as well. Tread patterns matter on the outsole. You need multiple contact points with the surface blended with channeling patterns to keep the dangerous water or spill from gathering under foot. The “channels” help displace the liquid on contact.

Always hold your safety footwear provider accountable for the validated slip resistance ratings of the shoes in your program. You may not understand how the ratings are established or determined, but you now understand that setting a standard for your work environment does matter and can make a big difference in your employees safety. And use the ratings for oily/wet and not simply wet. Remember, a .35 oily/wet is safer than a .35 wet and much safer than a .35 dry.