How Is Slip Resistance Tested in Safety Shoes?

Slip incidents at work cause thousands of injuries every year¹. The label on your shoe says "SRC." But do you actually know what that means — and whether it protects your workers?

Slip resistance in safety shoes is tested by measuring the coefficient of friction between the outsole and a specific surface. The EN ISO 13287 method tests two surfaces: ceramic tile with soapy water (SRA) and steel plate with glycerol (SRB). A shoe that passes both earns the SRC rating under EN ISO 20345.

I have been in the safety shoe industry for over 20 years. I have seen buyers make the same mistake over and over — they trust the label and stop asking questions. This article breaks down what the tests actually measure, what the ratings actually mean, and what happens to grip after six months of real use. If you are sourcing safety shoes for industrial use, this is the article you need to read before placing your next order.

What Standards Are Used to Test Slip Resistance in Safety Shoes?

Most buyers treat certification as the finish line. In my experience, it is only the starting line.

EN ISO 20345 requires slip resistance testing for safety footwear sold in Europe². The test follows EN ISO 13287, which measures friction on controlled surfaces in a lab³. The results are reproducible, but they only reflect performance on two specific surfaces — not the full range of floors found on real job sites.

The standard is designed to be consistent and comparable. That is its strength. But that is also its limitation. A controlled lab surface is nothing like a food processing plant floor, a steel grating platform, or a wet concrete loading dock. The standard does not separate these situations. We have to do that ourselves, before production even starts.

I remember a client from the Middle East who came to us in 2022. He had already ordered 2,000 pairs from another supplier. The shoes passed EN ISO 20345. But within three months, his client — a food processing plant — reported six slip incidents on wet ceramic tile floors. No serious injuries, but the buyer cancelled the next order immediately. That supplier lost a $180,000 contract because they never asked one simple question: what floor surface do your workers actually stand on?

When I take on a new client, that is always my first question. The standard gives you a baseline. Your client’s actual floor gives you the real requirement. These two things are often very different.

Ceramic tile with soapy water is a completely different problem from steel grating with machine oil. The standard does not separate these two situations. We have to do that ourselves, before production even starts. If your supplier is not asking about your actual floor surface before recommending a product, that is a serious gap in their process.

What Do SRA, SRB, and SRC Mean on Safety Shoe Labels?

SRC looks like the best rating. And it is — on paper. But most buyers miss what is behind those three letters.

SRA means the shoe passed a friction test on ceramic tile with soapy water. SRB means it passed on a steel plate with glycerol. SRC means the shoe passed both tests. Under EN ISO 20345, SRC is the highest slip resistance classification, but it still only covers two specific surface-contaminant combinations.

The SRC label is useful. But it does not tell you the shoe will perform on every surface in your facility. I had a client in Germany — a PPE distributor — who was selling SRC-rated shoes to food processing facilities. His end users started reporting slips on wet rubber conveyor mats. He called me frustrated, thinking the certification was wrong. It was not. The shoe simply was not designed for that surface. The SRC label told him the shoe passed two specific tests. Nobody told him those two tests did not cover rubber mats.

We spent two weeks back and forth, testing three different outsole compounds on rubber mat samples he sent to us. The third compound — a softer nitrile blend with a wider tread channel — reduced the slip rate to near zero in his facility’s own internal test. He reordered 1,500 pairs within the month.

Here is how the three ratings compare in practical terms:

The lesson is simple: match the test surface in the certification to the actual surface in the facility. If they do not match, the SRC label means very little in practice. Always ask your supplier which specific floor environment a shoe has been validated for — not just which certification it carries.

How Does Outsole Material Affect Slip Resistance Performance?

The outsole is where slip resistance is actually built. Not in the testing room. Not on the label.

Outsole material directly determines grip because it controls two things: how much surface contact the rubber makes with the floor, and how quickly the tread channels evacuate liquid. Softer rubber compounds generally provide better wet grip⁴. Wider, deeper tread channels reduce hydroplaning on wet surfaces.

Most manufacturers chase hardness because harder soles last longer and cost less to produce. But hardness kills grip. A rubber compound rated Shore A 75 holds up for 18 months. A compound at Shore A 60 gives you around 30% better wet grip but wears faster⁵. That trade-off is real, and most buyers are never told about it.

What most buyers also never see is the tread channel design. The channels need to evacuate liquid fast enough to keep the rubber in contact with the floor. If the channels are too shallow, the shoe hydroplanes — exactly like a car tire in rain⁶. I once rejected an entire batch of outsole molds in our factory because the channel depth measured 0.3mm short of our internal specification. My QC team flagged it. Some people thought I was being too strict. But 0.3mm across 3,000 pairs means 3,000 pairs that underperform in wet conditions. I sent the molds back.

We use a nitrile rubber blend for most of our slip-resistant outsoles. Pure rubber gets brittle below -10°C and loses grip fast⁷. Pure PU performs well dry but drops significantly when wet⁸. Our blend sits at Shore A 62, which we arrived at after testing 11 different compound formulas over about eight months. That number did not come from a catalog. It came from worn soles that clients sent back to us, and from our own internal wear tests. The tread design and the compound formula work together. You cannot optimize one without considering the other.

How to Test Slip-Resistant Shoes?

The formal test is useful. But it only tells you half the story.

To test slip resistance in safety shoes, the standard method is EN ISO 13287, which measures the coefficient of friction on defined surfaces under controlled load and speed. For real-world validation, accelerated wear testing and field sample collection after 6 to 12 months of use provide far more accurate performance data.

EN ISO 13287 is the method behind the SRA, SRB, and SRC ratings. It measures friction under controlled conditions — specific surface, specific contaminant, specific load. The results are reproducible and comparable across manufacturers. That is the value. But the test only captures one moment in the shoe’s life: day one, brand new, straight out of the box.

What it does not capture is what happens at month six. Tread depth on a new outsole is typically 4 to 6mm. After six months of daily use in a warehouse or factory, that can drop to 1.5mm⁹. At that depth, the channeling system that evacuates liquid is essentially gone. The coefficient of friction drops sharply — sometimes by 40% or more — but the shoe still looks fine from the outside. Workers keep wearing it. That is when accidents happen.

In our factory, we run accelerated wear tests that simulate 12 months of use before a new style goes to market. We also ask clients to send back worn pairs after six months in the field. Most manufacturers test once, certify, and move on. We have collected over 200 worn pairs from clients across eight countries in the past four years. That data tells us more about real-world performance than any lab test. It is also how we improved our current outsole compound twice in three years — without changing the design, just the formula.

Conclusion

Slip resistance testing starts with certification but does not end there. The real answer comes from the floor surface, the outsole compound, and actual wear over time. At Shoegan, we build slip resistance into every compound decision, every tread spec, and every pair — because protection that fails at month six was never really protection at all. Contact us at [email protected] to discuss the right outsole solution for your specific job site conditions.