Comparison of Flexible Pavement Distresses Monitored by North Carolina Department of Transportation and Long-Term Pavement Performance Program

The Long-Term Pavement Performance (LTPP) program has collected pavement distresses for general pavement study (GPS) sites throughout the country. These sites were used in the initial calibration of the Mechanistic–Empirical Pavement Design Guide, so it is important for states to compare their distress identification procedures and results with the LTPP distresses as part of the local calibration process. North Carolina has 24 GPS sites, of which four are concrete, one went out of service very early, and the remainder are flexible pavements. This paper focuses on the flexible pavement distresses. The GPS sites are 500-ft sections of much longer roadways. The LTPP distress data were extracted for the North Carolina Department of Transportation (NCDOT) GPS sites. Corresponding locations and their distress histories were pulled from the NCDOT pavement management system. In addition, rut depth measurements taken by high-speed profilometer were obtained for many of the sections for comparison with LTPP rut depth measurements. As might be expected, the LTPP walking survey revealed higher amounts of distress than the NCDOT windshield survey. Alligator cracking is the major distress for NCDOT pavements, and a roughly two-to-one relationship was found between alligator cracking by LTPP compared to NCDOT. Rut depths measured by LTPP were also found to be larger than those measured by high-speed profilometer, but in either measure, rut depths measured for NCDOT sections were low (less than 10 mm for all sites).