The main objective of this project is to quantify and resolve the differences in the longitudinal profile and roughness indices that are attributable to the different profiling equipment that have been used in the LTPP program. The Long-Term Pavement Performance (LTPP) program was designed as a 20-year study of pavement performance. A major data collection effort at LTPP test sections is the collection of longitudinal profile data using inertial profilers. Three types of inertial profilers have been used since the inception of the LTPP program:

(1) K.J. Law Engineers DNC 690 incandescent profilers,
(2) K.J. Law Engineers T-6600 infrared-system profilers, and
(3) ICC laser profilers.

The following analyses were performed for this research project:

(1) investigate data collection characteristics and compare profile data collected by the different inertial profilers,
(2) compare International Roughness Index (IRI) values obtained by the different inertial profilers,
(3) investigate factors that contribute to differences in IRI for data obtained from profilers and Dipstick®, and
(4) identify problems with equipment functionality and current data collection and processing procedures. The analysis indicated good agreement of IRI values among the different inertial profilers that have been used in the LTPP program.