A Surface Dynamics Profilometer was acquired in December 1968. The SD Profilometer was designed to rapidly and accurately measure the profile of the surface over which it is driven. A Quarter-Car Simulator was obtained in 1970. The simulator, a special purpose analog computer, was designed to process road profiles measured with the SD Profilometer. This processing involves analog simulation of a simplified vehicle. Factors and variables associated with the devices and calibration and test procedures were investigated and standardized. The Automatic Roughness-Measuring System using an automobile (Kentucky interim standard method of test for roughness) was correlated with the SD Profllometer - QC Simulator system to permit continued assessment of pavements previously tested with the automobile.

Precision of the SD Profilometer and QC Simulator was demonstrated by repeated testing of several pavements. Pavements with the higher roughness indices exhibited about the same standard deviation as pavements with lower roughness indices. On a percentage basis, therefore, the measurement precision was better for a rougher pavement than for a smoother pavement. A single measurement was within three percent of the sample mean 95 percent of the time. The roughness index obtained by simulating the Bureau of Public Roads Roughometer within the QC Simulator system was selected as the best expression of road roughness.

Report Date


Report Number

No. 465

Digital Object Identifier



The contents of this report reflect the views of the authors who are responsible for the facts and the accuracy of the data presented herein. The contents do not necessarily reflect the official views or policies of the Bureau of Highways or the Federal Highway Administration. This report does not constitute a standard, specification, or regulation.