Effect of road texture characteristics on skid resistance: parametric study viathe DFM

Skid resistance is related to the friction generated between car tyres and the road surface. It enables drivers to shorten their stopping distances and to follow their desired trajectories along a road. It depends as much on the road surface characteristics, as on the car tyres and the operating conditions. For the road surface, texture remains the main parameter governing its contribution to skid resistance. This texture is composed of a multitude of irregularity scales, but two of them (Macrotexture and Microtexture) are mainly considered to contribute to skid resistance. The work proposed within this paper aims to proceed to a study to identify the exact role of Macrotexture and Microtexture on a road surface, by investigating the effect of different smoothing levels upon these scales using the ‘Dynamic Friction Model’ (DFM), a computational skid resistance model recently developed. The smoothing procedure of the road surface is conducted as following: •The original profile of the road surface is decomposed via an Empirical Mode Decomposition method (part of the Huang Hilbert Transform (HHT)) to a multitude of constituent fundamental profiles of different scales termed “Intrinsic Mode Functions” (IMF). •The first IMF is subtracted from the original profile to give derive to a smoother profile. •The second IMF is subtracted from that smoothed profile to derive a further second even smoother profile. Accordingly, the derived two new profiles displays the texture within different Macrotexture and Microtexture. The DFM is then applied to these new profiles to highlight the role of the respective two roughness scales. The results from these simulations show that for two wet road surfaces with the same Macrotexture, the higher the Microtexture can be maintained, the better the skid resistance will be at all speeds, even at a speed limit at which the skid resistance will start to drop. Furthermore, for two wet road surfaces with same Microtexture, the higher the Macrotexture can be maintained, the later hydroplaning will occur