Using the International Roughness Index for Profilograph Trace Reduction

Current Louisiana acceptance specifications for 100 percent payment require Profile Indexes (PIs) completed pavement surface to as low as 3.0 in./mi for flexible pavements and 6.0 in./mi for rigid pavements. These acceptance specifications are currently among the most stringent in the United States. Requiring an acceptance PI value of less than 7.0 in./mi when using the California-style profilograph and the 0.2 in. blanking band is unacceptable unless the blanking band is eliminated from the procedure. Louisiana's efforts to replace the blanking-band evaluation procedure with a procedure that inputs the profile trace into the quarter-car-based International Roughness Index (IRI) model are presented. The key step in this process is the scanning and digitization of the profilo-gram before determining the IRI based on the filtered profile trace. A much better correlation exists between the rideability of the finished surface and the profilograph IRI than that of the profilograph PI. New profilograph IRI specifications are recommended to replace the existing PI specifications.