Oregon DOT is transitioning to use the International Roughness Index (IRI) for an incentive-disincentive program for pavement smoothness evaluation for newly paved roads. The IRI will typically be determined by contractors using inertial profilers. This research evaluated the procedures, site, and equipment used for establishing a reference profile for a certification process for inertial profilers. In a comparison of several profiling devices, the inclinometer-based profiler used by Oregon DOT for the reference profile showed sufficient results in repeatability and accuracy in profile measurement and calculation of IRI. However, the certification site shows significant variability in IRI across the site, which can lead to lower accuracy scores when the exact path is not followed. Further, significant differences in IRI were observed during repeat visits throughout the course of the study period. This study also evaluated the use of a new technology, terrestrial laser scanning, for pavement analyses. At larger extents, terrestrial laser scanning (TLS) was compared to several current techniques to measure road profiles including digital levels, inclinometers, and inertial profilers. TLS is able to collect a large, dense set of data relatively quickly for the entire roadway and surrounding areas; hence, the data can not only be used for evaluating the pavement roughness but also can be used for other design parameters such as transverse and longitudinal slope. The results show that profiles derived from TLS data determined accurate IRI values and cross-correlation with the reference profile. At a finer scale, micron resolution 3D laser scanners can be utilized to determine the influence of predominant aggregate size on the texture of the pavement.
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