ROAD ROUGHNESS: ITS ELEMENTS AND MEASUREMENT

The purpose of this paper is to summarize the importance of rational and compatible measurements of road roughness and to point out some of the problems of and possible methods for making such compatible measurements. Some ideas are also set forth for a general roughness index that could be used on a worldwide basis for comparing roughness of both paved and unpaved surfaces and for evaluating both road serviceability and vehicle operating costs. It is intended to provide an assessment of the current state of the art and a comparative evaluation of alternative surface (paved and unpaved) roughness measurement methodologies, with particular attention to evaluating and using the important relationships between vehicle operating costs and road surface condition. There is a need for a common scale for measuring roughness. First, we must be able to compare results of research on vehicle operating cost relationships from several research studies (for example, in Kenya, Brazil, and India) and to evaluate the magnitude and nature of errors associated with applying relationships developed in one country to other countries. Second, if we apply the vehicle operating costs and road deterioration relationships to other countries (which is already being done), then we obviously need to measure roughness on a common scale. (Author)