The reflectivity characteristics of a road surface are crucial to the luminance design of highway lighting systems. At present, the reflectance matrices used for design calculations are obtained by experimental procedure and contain important information about the pavement surface texture. In this paper is described a model built on the theory of dispersion of electromagnetic waves by random rough surfaces in a high-frequency approximation, as applied to pavements. The model explains the reflectanceM~ properties of pavements on the basis of the statistical characteristics of the surface texture and the physical properties of the pavement mix. To test the model, measurements were done on the Ontario road reflectance matrix photometeEMr at the University of Toronto. When tested and calibrated, the model showed good agreement between predicted and measured data. The backscattering of ultrasonic waves by pavement surfaces is discussed in terms of low-frequency approximation of the theory of scattering from random rough surfaces. Simple experiments, using scale models, showed gMMMZood correlation between the intensity of backscattering from the pavement surface and its skid resistance. The model can be used to extract statistical surface texture characteristics from experimental data for the assessment of other properties of pavements, such as skid resistance or pavement wear.(A).
Abstract