Test Method

Why IceGrip?

Every year, more than 25,000 people in Sweden are injured after slipping on ice or snow. According to a report from the Swedish National Road and Transport Research Institute (VTI), slip-and-fall accidents related to snow and ice cost society SEK 22 billion every year. Just over SEK 360 million can be attributed to direct costs such as hospital care, lost productivity and administration, while the majority is linked to psychological suffering and society’s loss of welfare in cases of fatalities.

The risk of slipping decreases significantly if you wear the right type of shoes. That is why Testfakta, together with the Swedish research institute RISE, has initiated a project focused on high-grip footwear. The test method is an international standard developed by the Swedish research institute RISE to develop and verify what qualifies as high-grip winter footwear. The test produces an Ice Grip Index.

 

How the test works

By measuring at what angle a sole pressed against a slippery surface no longer grips, it is possible to determine the shoe’s traction. The test is carried out using a tribometer in accordance with Swedish Standard 657177:2024 and can be divided into four steps:

  • • The outsole is separated from the upper and cooled to just above 0°C.
  • • The sole is placed in the tribometer, which is positioned on an asphalt slab covered with a thin layer of ice.
  • • The sole is pressed against the ice at a 0° angle, i.e. straight down onto the ice surface.
  • • The angle is adjusted and the sole is pressed down onto the ice again.
  • • This is repeated until the sole no longer grips and instead slides on the ice.

The higher the angle the sole can withstand without slipping, the higher the Ice Grip Index.

 

Testfakta has, based on the Ice Grip Index measurements, developed a labelling system for shoe traction on ice. In order to be classified as high-grip and recommended for winter conditions, the sole must have an Ice Grip Index above 5. The rating scale consists of five steps, where soles with a rating of 3 or higher (i.e. an Ice Grip Index above 5) are approved and may carry the Testfakta IceGrip label.

Betygsskala

What makes a pair of shoes slippery?

1. Hardness

A soft sole is generally considered to provide better grip against the ground than a hard sole, especially on ice. However, it must not be too soft, as it may become overly springy and uncomfortable or unstable to walk in. It is also important to consider that hardness varies with temperature. A sole that feels soft in a store can become hard when cooled down, depending on the material it is made from. That is why we have measured sole hardness both at warm temperature and in cold conditions. Hardness is measured on the Shore scale.

2. Tread pattern

A deeper tread pattern is generally considered beneficial for better grip, for example when walking off-road or in soft snow. But when it comes to slipping on ice, the contact surface area is crucial: the more tread pattern a sole has, the smaller the contact area with the ground. That is why we see that shoes with a coarse tread pattern generally perform slightly worse on black ice than shoes with a finer tread pattern. However, the sole must not be completely smooth either, as that also increases the risk of slipping.

3. Chemical composition

The chemical composition of the sole is also important for traction. This includes the rubber content as well as additives such as different types of granules, carbon or silicone, which often provide somewhat better grip on ice.

 

Thanks to participating companies and organisations

Testfakta would like to express its sincere thanks to the companies that have contributed shoes for the initial tests. The products were provided free of charge for testing purposes. Providing test samples has not influenced the selection, execution or assessment of the test. All products have been tested using the same methodology and evaluated independently and in a comparable manner.

 

The IceGrip project is partly funded through financial support from Skyltfonden, administered by the Swedish Transport Administration (Trafikverket). The positions, conclusions and working methods in the project and final report reflect Testfaktas views and do not necessarily align with Trafikverket’s positions, conclusions or working methods within the scope of the report’s subject area. 

How the test is conducted

How is a shoe’s outsole tested, and what does the Ice Grip Index mean?
Read more

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