Assessment of Virginia's Hybrid South Dakota Road Profiling System

About the report:

South Dakota Road Profiling (SDRP) systems have been widely sanctioned for use in assessing road roughness and rutting at highway speeds. Traditionally, these high-speed profiling systems have been built around ultrasonic height sensors. More recently, some designs have begun to substitute laser sensors to combat many of the limitations of sound-based equipment. The functional improvements possible with lasers are expensive, however. Whether the potential of lasers for high-speed profiling justifies the great increase in cost was a legitimate question. This report describes the steps that the Virginia Department of Transportation took to address that issue. In general, this research has found that both sensor types are capable of performing very well and with reasonable agreement. Repeatability tests indicated that the roughness indices calculated from laser-based profiles are less subject to run-to-run variability than those developed from ultrasonic profiles. Tests to evaluate the effects of vehicle speed and sampling rate on the estimate of roughness have returned less conclusive results. Both tests suggested that the ultrasonic-based data was more highly correlated with the control data (i.e., that based on data collected with the Face Companies' Dipstick R) than the laser-based. The laser data, however, could be shown to be slightly more accurate, on average, than that based on the ultrasonic. Unfortunately, although the performance of the ultrasonic sensors on conventional surfaces has been adequate, their reliability has become a serious concern. In Virginia, humid surveying conditions are often unavoidable, and the problem of wet ultrasonics has become more than a simple inconvenience. Hardware reliability may be the most compelling reason to migrate to pure laser roughness measurement. The adoption of only laser-based equipment in future purchases or leases is recommended.

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