Skid Resistance

Skid resistance refers to the contribution of the road surface to tire/pavement friction. In addition to friction, it involves the phenomena of lubrication and wear. It is therefore a field of application of tribology that involves the tire tread and the road surface as surfaces in contact, and contaminants (water, snow, ice, etc.) as lubricants at the interface of these solids.

Tyre/road grip enables a vehicle to stay on course and brake/accelerate, whatever the road surface conditions, and is therefore synonymous with safety. When the road surface is wet, snowy or icy, grip is reduced and the risk of accidents is increased by at least a factor of two compared with dry road conditions. Wear and tear caused by traffic and weather further accentuates the loss of grip.

This article looks at the influence of contaminants and wear on skid resistance. The road literature abounds in studies and research on the influence of water and polishing on skid resistance; this craze stems from the historical need to prevent accidents due to aquaplaning or excessive polishing of aggregates. Here, we attempt to address contaminants such as snow and ice, which are less well studied –despite their importance in winter conditions –, and lesser-known wear mechanisms such as the ageing of bituminous materials or deterioration due to seasonal variations. A good understanding of these aspects (physical mechanisms, influencing factors, characterization) will enable us to better plan pavement maintenance, optimize the use of material resources and inform users of the risks involved.

The article deals with the skid resistance of road pavements, but the concepts covered (generation of friction forces by hysteresis and adhesion, water evacuation, macro- and microtexture of pavements, etc.) can be applied to other types of pavement subjected to tire traffic, such as airport pavements or subway rails.