Dynamic slip test testing is a laboratory procedure that measures the coefficient of friction between footwear outsoles and standardized floor surfaces under conditions that simulate real walking and slipping events. Performed in accordance with internationally recognized standards such as EN ISO 13287, ASTM F2913, and GB/T 3903.6, this test is essential for footwear safety certification, product development, and quality control. This article explains the technical principles, sample requirements, test items, methodologies, and typical applications of dynamic slip resistance testing.
Technical Overview
Dynamic slip test testing, also known as dynamic slip resistance testing, is a whole-shoe laboratory method used to quantify the anti-slip performance of footwear by measuring the dynamic coefficient of friction (COF) between the sole and a standardized floor surface. Unlike static slip measurements, which determine the force needed to initiate movement from rest, dynamic testing reproduces the continuous sliding contact that occurs during an actual slip, producing results that correlate more closely with real-world walking conditions.
The test principle is straightforward: a footwear sample mounted on a standardized last is pressed against a floor surface at a defined contact angle with a controlled vertical (normal) force, while the surface moves horizontally at a constant speed. The instrument records the horizontal friction force during the sliding phase, and the dynamic coefficient of friction is calculated as COF = Fh / Fv, where Fh is the measured horizontal friction force and Fv is the applied vertical force. A higher COF value indicates stronger slip resistance.
Slips, trips, and falls remain among the leading causes of occupational injuries worldwide, which makes slip resistance a critical safety and performance indicator for footwear manufacturers, PPE certification bodies, distributors, and end users. Dynamic slip testing is routinely carried out by accredited third-party laboratories in accordance with the following standards:
- EN ISO 13287 / ISO 13287 – Personal protective equipment – Footwear – Test method for slip resistance
- ASTM F2913 – Standard test method for determining the coefficient of friction of footwear on floor surfaces using a whole-shoe tester
- GB/T 3903.6 – Footwear – Test methods for whole shoe – Slip resistance (Chinese national standard)
- EN ISO 20344 and EN ISO 20345 – Test methods and requirements for safety footwear, which reference slip testing for SRA, SRB, and SRC slip resistance classification
Testing Samples
Finished Footwear (Whole Shoes)
Complete footwear is the primary test object because slip performance depends on the combined effect of the outsole compound, tread pattern, heel geometry, and overall shoe construction. Typical samples include safety shoes, occupational footwear, hiking boots, work boots, casual shoes, leather dress shoes, and sports shoes. Samples must be in unused condition and within the size range specified by the relevant standard, and they are normally conditioned in a standard laboratory atmosphere (typically 23 ± 2 °C and 50 ± 5% relative humidity) before testing.
Outsole and Sole Materials
During material development and supplier approval, molded outsole specimens and flat sole pads made of rubber, PU, TPU, PVC, TPR, EVA, or blended compounds can be evaluated. Material-level screening helps compound engineers compare tread designs and formulations before tooling investment for full shoe production.
Specialty and Professional Footwear
Chef and kitchen footwear, healthcare and cleanroom shoes, firefighter boots, military and tactical boots, oil-resistant industrial footwear, and anti-slip consumer footwear are frequently tested to substantiate performance claims and to support certification in demanding service environments.
Testing Items
Dynamic slip test programs typically include the following test items, each reported as a dynamic coefficient of friction:
- Forward heel slip resistance (FHE mode) – simulates slipping when the heel strikes the ground during walking
- Backward heel slip resistance (BHE mode) – simulates rearward loss of grip on the heel
- Flat or forepart contact slip resistance – evaluates grip over the main sole contact area
- Dry surface slip resistance – tested on dry steel plate and/or glazed ceramic tile
- Wet surface slip resistance – tested with water as the contaminant
- Contaminated surface slip resistance – tested with glycerol solution or dilute sodium lauryl sulfate solution as specified in the standard
- Slip resistance classification – SRA, SRB, or SRC marking assessment in accordance with EN ISO 20345
Testing Methods
Testing is performed on a whole-shoe dynamic slip resistance tester consisting of a rigid frame, a shoe-holding last assembly with adjustable contact angle, a force application system, a motorized moving platform carrying the floor specimen, and a data acquisition system. The general procedure is as follows:
- Sample conditioning: footwear is conditioned in the specified laboratory atmosphere to stabilize material properties.
- Surface preparation: standard floor surfaces, typically a smooth steel plate and a glazed ceramic tile, are cleaned and mounted on the moving platform; contaminants are applied where required.
- Mounting and positioning: the footwear sample is fitted onto the last and inclined to the specified contact angle for the selected slip mode (for example, 7° for heel-contact tests per EN ISO 13287).
- Force application: a defined vertical normal force is applied through the last, commonly 500 N ± 25 N for adult footwear per EN ISO 13287.
- Dynamic sliding: the platform moves relative to the shoe at a constant speed, typically 0.3 m/s, while the horizontal friction force is continuously recorded.
- Calculation and reporting: the dynamic coefficient of friction is computed as the ratio of the recorded horizontal force to the vertical force over the defined measurement zone; repeated runs are averaged for each shoe, mode, surface, and contaminant combination.
For acceptance purposes, EN ISO 20345 requires a mean coefficient of friction of at least 0.32 under the applicable test conditions for the SRA (ceramic tile with soap solution), SRB (steel with glycerol), and SRC (both SRA and SRB satisfied) classifications. ASTM F2913 and GB/T 3903.6 report measured COF values under dry and wet conditions, which are then interpreted against buyer specifications, benchmark products, or internal acceptance criteria, since these methods do not impose a universal pass/fail threshold.
Applications
Dynamic slip test results are used across the footwear value chain for multiple purposes:
- PPE conformity assessment and certification support for safety footwear under EN ISO 20345 and related regulatory frameworks
- Research and development of outsole tread patterns, heel geometry, and rubber or polymer compounds
- Incoming material inspection and production batch quality control by manufacturers
- Supplier verification and comparative benchmarking during sourcing and procurement
- Substantiation of marketing claims such as "anti-slip," "slip-resistant," and "oil-resistant" footwear
- Technical support for slip-and-fall accident investigations, forensic analysis, and product liability assessments
- Fundamental research into footwear–flooring interaction and contaminant effects on traction
FAQ
What is the difference between static and dynamic slip testing?
Static testing measures the friction force required to initiate sliding from a stationary position, whereas dynamic testing measures friction while continuous relative sliding occurs. Dynamic testing better represents the conditions of an actual slip during walking and is therefore the preferred method for whole-shoe slip resistance evaluation in most international standards.
What coefficient of friction is considered acceptable?
Under EN ISO 20345, safety footwear must achieve a mean COF of at least 0.32 in the applicable SRA or SRB test condition to qualify for SRC-level classification. In practice, many brand specifications and end users in high-risk industries require higher values, commonly 0.40 or above, for wet or oily environments. Acceptance criteria should always be agreed between manufacturer and buyer based on the intended use environment.
Which surfaces and contaminants are used in the test?
The standard test surfaces are a smooth steel plate and a glazed ceramic tile, selected to represent common industrial and commercial flooring. Tests are conducted under dry conditions or with specified contaminants, including water, glycerol solution of the specified viscosity, or a dilute sodium lauryl sulfate solution, depending on the standard and classification being assessed.
How many samples are needed and how long does testing take?
Typically two to three pairs of unused footwear in the specified size range are required to cover the intended modes, surfaces, and contaminants. After conditioning, the mechanical testing itself is usually completed within a few working days, with exact turnaround depending on the number of test conditions and the laboratory workload.
Can results from different standards be directly compared?
No. Test parameters such as contact angle, normal force, sliding speed, surface type, and contaminant differ between EN ISO 13287, ASTM F2913, and GB/T 3903.6. COF values are only comparable when generated under the same standard and the same test conditions, so the standard and configuration must always be stated alongside reported results.
