Counties and other local highway agencies continually use visual or subjective rating systems for routine and periodic road Inspections. In a study of unpaved roads in Indiana, a subjective rating of unpaved roads was evaluated. Using a rating scale ranging from 0 to 5 for worsening road condition, regression relationships were determined among a panel condition rating and measured road roughness number, average rater speed and visually rated corrugation, potholes, rutting. and gravel looseness. As expected, the panel condition rating worsened with increasing roughness, and average rater speed decreased with increasing panel condition rating. However, because most of the roads studied were in reasonable condition, considerable reduction in average speed was not experienced. An examination of road distresses also showed that corrugations and potholes were more related to panel condition rating than the other distresses. The results were used to suggest a basis for selecting maintenance activity based on the panel condition rating, present serviceability rating, roughness, and average speed. A comparison of ratings by the study panel from Purdue and panels from two countries indicated that the county panels generally rated their roads to be in better condition than the Purdue panel. However, in any subjective rating, consistency within any group is the most important consideration.

Over the years visual or subjective assessment of road condition has been the traditional method of inspection by highway engineers. Application of a visual assessment procedure requires experience and a knowledge of maintenance and improvement practices that apply to identified distresses. Several attempts have been made to quantify these visual ratings by using numeric ratings to represent pavement and surface conditions. Such subjective numeric ratings have also been related to measure roughness and other measurable road surface distresses, such as cracking and patching, as well as rut depth