Analysis of Influences on As-built Pavement Roughness in Asphalt Overlays

Pavement roughness immediately after construction is a key measure of quality. The use of smoothness specifications requires an understanding of the influences on as-built roughness for both transportation agencies and contractors. This paper uses data from the Long-Term Pavement Performance (LTPP) program to examine four factors to determine their effects on the as-built roughness of a pavement. These factors include the extent of surface preparation prior to resurfacing, overlay thickness, type of overlay material and pavement roughness prior to resurfacing. Various statistical procedures including paired data analyses, regression analyses and a repeated measures analysis are performed to investigate these effects and any interactive effects. The extent of surface preparation, overlay thickness and pavement roughness prior to resurfacing are determined to have statistically significant effect (at a 95 % significance level) on the as-built roughness of a pavement either directly or interactively with another variable. The overlay mix type is determined not to have an influence on as-built pavement roughness. Data from the Canadian Long-Term Pavement Performance (C-LTPP) program is used to validate the results for overlay thickness and pavement roughness prior to resurfacing. A series of prediction equations are also developed to allow for estimating the as-built roughness of a pavement under various conditions. Pavement designers, construction engineers and contractors should understand the effects that influence the as-built roughness of a pavement so that they can maximize their designs, smoothness specifications and/or bidding of contracts with smoothness specifications.