Estimation of road surface roughness

Different phases of water (ice, snow and their mixes) have different resonance frequencies and it has previously been shown that these differences are greatest at near infrared wavelengths (1-2 µm). Hence, a sensor with three different laser wavelengths in this span has been developed and tested on real winter roads. The results show that it is possible to distinguish between different road conditions like snow, ice and water on an asphalt road, see figure 1. Further, to determine the surface roughness a model of light reflection from soils is applied on the reflections in different directions from the surface. This results in a measure of the roughness, which together with the surface material is the most important parameter to correctly determine road friction.

Ideas have also been evoked to combine the results from the surface measurements with additional information in order to determine the road friction more accurate. Such additional information could for example be the temperature. In this work collaboration with project 3-4 in CASTT is important.