What can be stated in this project is how a winter road is experienced when compared to snow free conditions, primarily with regard to unevenness and noise. Surveys carried out during the project show that it is possible, without too much difficulty, to measure the unevenness of a snow covered road surface. In this report is winter road defined as a snow covered road (around one day after heavy snowfall). Based on survey results, the study shows that the unevenness of section lengths between 0.05 metres and 1.0 metres are most affected by winter road conditions. Unevenness during winter road conditions is approximately five times greater than that experienced during snow free conditions. However, it is impossible to generalise for an entire road network as surface conditions during winter can be extremely variable. It is also possible to see that the surface structure described by the shortest wavelengths investigated, less than 10 millimetres, is smoother on the snow-covered surface. This is one hypothesis and indicates that measurements are reliable. The link between noise and unevenness is related to vehicle speed. The biggest sound difference between winter and summer road conditions, which could be related to the road surface measurements, was at the lower frequency range. Perceived in-car noise levels were between 3 and 6 decibel higher during winter conditions. However, for the higher frequency range the difference in noise levels was opposite - lower levels during winter conditions. A possible explanation for this is that sound may be absorbed by the snow. (Author/publisher)
Samenvatting