Theoretical Study on Recognition of Icy Road Surface Condition by Low-Terahertz Frequencies

Recognition of road surface conditions should always be at the forefront of intelligent transportation systems for the enhancement of transportation safety and efficiency. When road surfaces are covered by ice or snow, accident rate would increase due to the reduction of road surface roughness and also friction between tire and road. High-resolution recognition of natural and man-made surfaces has been proved to be achievable by employing radars operating at low-terahertz (low-THz) frequencies. In this work, we present theoretical investigations on surface condition recognition of an icy road by employing low-THz frequencies. A theoretical model combining integral equation method (IEM), radiative transfer equation (RTE), and Rayleigh scattering theory is developed. Good agreement between the calculation results and measured data confirms the applicability of low-THz frequencies for the evaluation of icy road surface in winter. The influence of carrier frequency, ambient temperature, impurities inside the ice layer, and frozen soil surface conditions on the efficiency of this method is presented and discussed.