An empirical model of roughness progression is developed that differs in form from traditional performance and pavement design models, which attribute roughness changes only to structural factors, andfrom correlative models, which have often been unable to distinguish any causative factors other than age or environment. The incremental change in roughness is modeled through three groups of components, dealing with structural, surface distress, and environment-age-condition factors, respectively. The formulation and components were estimated statistically from field data of a very comprehensive factorial of in-service pavements in the major brazil-united nations development program (undp) road costs study. It was evident from the datathat road roughness develops through multiple mechanisms, and the model resulting from detailed nonlinear statistical analysis shows that significant deterioration can occur even in the absence of structural weakness. This has important implications for pavement and rehabilitation desin. Roughness progression follows a generally accelerating trend, with the rate of progression depending initially upon the rate of traffic loading relative to the pavement strength and on the environmental coefficient, and then rising more rapidly once surface defects such as cracking, potholing, and patching occur. Across-country and across-climate studies on independent data sets have quantified the macroclimatic effects and shown the model to be highly transferable. This paper appears in transportation research record no. 1215, Pavement management and rehabilitation.
Abstract