Questioning the approach to predict the evolution of tire/road friction with traffic from road surface texture

The paper points out the limits of current approaches to predict the evolution of skid resistance over time from the road surface texture. Simulation in laboratory of traffic-induced polishing shows that the friction coefficient measured on an asphalt concrete first increases, reaches a maximum then decreases. In the meantime, texture parameters evolve in a scattered way and do not reflect the friction evolution. Comparison of scanning electron photos at different polishing stages reveal cracking in the bitumen layer and the aggregates and fracture at late polishing stages. These findings prove that wear of road surfaces results from more complex processes than just a modification of the surface texture. Considering asphalt concretes as a coated system, with the bitumen deposited as a coating on the substrate composed of aggregates, a more systematic approach is derived to better understand the basic mechanisms. At the micro-scale, similarities in terms of debris formation allows to assume that fatigue wear induces the damages observed in the microstructure. At the macro-scale, this process translates into an evolution of the wear depth, which also highlights the effect of the aggregate roughness in the removal of the bitumen layer. Discussions are finally made on a friction model developed for coated surfaces and its application to predict the evolution of tire/road friction. The proposed study and its first findings show that there is a need to reconsider the texture-friction relationship; this questioning allows to look at an asphalt concrete from a different perspective-considering it as a coated system-and open perspectives for future research.