ROAD PROFILES, VEHICLE DYNAMICS, AND HUMAN JUDGMENT OF SERVICEABILITYOF ROADS - SPECTRAL FREQUENCY-DOMAIN ANALYSIS

The serviceability rating of roads has been an interesting and importa nt subject ever since it was introduced to measure the road performanc e. The present paper analytically addresses this problem-namely, linki ng a static road profile with the dynamic response of a vehicle to the existing road profile and to the driver's impressions and evaluation of the ride character on the road. Using a quarter car model and apply ing the spectral density method, analytical expressions have been deri ved for various response dynamic indices, such as jerk index, accelera tion index, average rectified speed (ARV), average rectified slope (AR S), and the international roughness index (IRI), in terms of the perti nent physical parameters of the road and the dynamic characteristics o f the quarter car. A general expression for serviceability index of ro ads is suggested using Fechner's psychophysical law and is verified us ing field data.