Characterization of road microtexture by means of image analysis

Road-surface microtexture (sub-millimeter scale) is essential for pavement skid-resistance. However, its measurement is only possible in laboratory on cores taken from trafficked roads, and is time consuming. For an efficient road monitoring, it is necessary to develop faster methods and usable on-site. Collaboration has been developed for two years between LCPC and the laboratory Signal, Image and Communication (SIC) to develop a measurement and characterization method for road microtexture based on image analysis. This paper deals with tow complementary works: The measurement of road microtexture. Research is focused on the image measurement and extraction of roughness information from images. The prototype using a high-resolution camera is described. The procedure separating relieffrom aspect-information using a photometric model for the surface is given. Image-based relief variation is compared to relief variation obtained through laser sensor. The characterization of road microtexture. This characterization, obtained through a geometrical and frequential analysis of images, leads to descriptors related to the shape and the density of surface asperities. Experimental campaigns were carried out to validate the feasibility of measuring on-site images and to correlate surface descriptors to friction. Results are presented and discussed. Perspective for future works is given.