Reference section for measuring systems to record the skid resistance of road surfaces
The skid resistance affects road safety in particular
Skid resistance describes the effect of the road surface texture on the traction between vehicle tyres and the carriageway. It has a crucial influence on driving safety. The skid resistance is measured by a fast moving vehicle using the lateral force measurement procedure (SKM).
To record skid resistance in the most realistic and comparable way possible, measurements are conducted under specified conditions using special measurement tyres. Using a device that wets the road, a defined film of water is applied to the carriageway ahead of the measurement tyres. The water required for this is carried along in a storage tank. During the test run, the lateral force acting on the angled measuring wheel in the direction of the measuring wheel axle is measured using a load cell. The ratio formed from the lateral force and the wheel load (normal force) corresponds to the lateral force coefficient, which is used to describe the skid resistance.
So as to ensure a comparable measurement quality, BASt regularly checks all SKM vehicles that conduct measurements of skid resistance within the course of road monitoring and assessment (ZEB) and/or the field of construction contracts.
The reference section established in the northern part of the duraBASt consists of five subsections with different, representative levels of skid resistance. The desired level of skid resistance was adjusted by deliberately varying the grit (type of aggregate, grain size, polishing resistance) or by grinding the wearing course which enables a wide variability of the texture ranges (micro and macrotexture) which are important for skid resistance to be obtained. Due to the very low polishing effect as a consequence of the negligible traffic load on the reference section, the levels of skid resistance remain constant for a long period, and are merely masked by seasonal effects.
The implementation of the skid resistance section represents an important step towards a calibration section for SKM measurement vehicles that remains unchanged over a long period of time. The inspection within the quality assurance process can now be performed with defined and very different levels of skid resistance. This firstly increases the informative value of the test, while secondly the skid resistance test can be expected to be much more accurate, because the permitted test tolerances can be more tightly defined given the considerably more constant ancillary conditions.