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.
HERMES – Harmonization of European Routine and research Measuring Equipment for Skid Resistance was a FEHRL-funded pre-normative project that aimed to lay the foundations for consistent European standardization of skid resistance measurement on roads and runways. Underlying the work was the idea that the project should give the initial impetus to the implementation of a common scale of friction, the so-called EFI (European Friction Index), together with an associated harmonized calibration procedure, in all European countries.