Factors Affecting Overlay Ride Quality

A study was conducted to identify the predominant factors that affect the achievable smoothness of asphalt overlays. The subject was approached from the perspective of a contracting entity (state highway agency). The basis of the study was a roughness survey that incorporated 4270 lane-km (2,650 lane-mi) and two full construction seasons with hot-mix asphalt concrete paving. Among the variables found to be related to the achievable smoothness were the functional classification (highway system), original surface roughness, and a special provision for smoothness. Variables that were found to be not significantly related to the smoothness achieved included surface mix type, the application of additional structural layers, the use of milling, and time-of-day restrictions on construction activities (i.e., nighttime paving).