Skid resistance / Slipperiness

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Relation between skid resistance and accident rate


A resin-bound surface dressing is an example of a road surface with a strong microtexture resulting in extremely high skid resistance at moderate speeds. That is why motorway slip roads with short radii of curvature are often constructed with a resin-bound surface dressing.

Skid resistance is defined as the frictional resistance at the interface between a vehicle tyre and the road surface. It plays an important part in the safety of road users: a correlation has been demonstrated between the skid resistance of pavements and accident rates (see the diagram opposite) [of course, there are many other possible causes of accidents: human error, vehicle technical failure, weather conditions, other infrastructure-related factors, etc.]. Wet pavement skid resistance is considered here, since dry pavement skid resistance is rarely a problem. A rough contact between the road and the tyres makes it possible to utilize the friction forces in braking. These friction forces also allow easier cornering. As a result, it is obvious that road managers should pay much attention to skid resisistance and alert road users in time of any local problem with poor skid resistance, and also that they should replace the pavement as soon as possible by an adequately skid-resistant pavement.

There are several factors affecting the skid reistance of a road pavement.

When constructing a new road surface, it is often checked whether skid resistance is satisfactory. During subsequent service as well road managers tend to monitor the development of skid resistance by periodic measurements, using a contact method that simulates vehicle behaviour under the most adverse conditions.

Microtexture can be measured accurately with contactless optical methods, but this way of determining skid resistance is still in the experimental stage.