This report proposes a framework for specifying coast-down test surfaces that will produce relevant, reproducible road load measurements. The proposed specification includes grade, roughness, megatexture, and macrotexture. Specification using standard scales in use by the pavement monitoring community is recommended for roughness (International Roughness Index), megatexture (“megatexture level” from ISO 13473-5), and macrotexture (Mean Profile Depth). These scales are well understood, and have demonstrated relevance to various type of vehicle response to the pavement. However, they may be replaced over the long term when other scales are developed with a specific emphasis on fuel consumption. The report also reviews commercially available equipment of measuring grade, roughness, megatexture, and macrotexture. This report presents a detailed survey of roughness values found on the public road system using data obtained from the Federal Highway Administration’s Highway Performance Monitoring System. The report also includes a tutorial presentation of road surface textures and some pavement design specifications that affect surface texture. (Author/publisher)
Abstract