In 2000, the Department switched to the International Roughness Index (IRI) as the base for the Roughness Distress Index. Because the South Dakota Roughness Index and the International Roughness Index emphasize the contributions of short- and long-wavelength roughness differently, the relationship between IRI and the Roughness Distress Index could only be approximated.
Because the original panel of experts comprised SDDOT personnel exclusively, their opinions may not have represented South Dakotas general public opinion. If the panel was more tolerant of pavement roughness than the general public, the importance of roughness might be underrated in the pavement management system. Conversely, if the panel was less tolerant of roughness, the importance of roughness might be overrated.
The uncertainty in how well the Departments Roughness Distress Index matches public perception and in the relationship of public perception to measured IRI casts uncertainty on the validity of pavement management decisions based on the measurements.