The New Jersey Department of Transportation (NJDOT), as many other DOT’s, moved towards utilizing a high-speed profiler to measure the International Roughness Index (IRI) as a part of the state smoothness acceptance specifications. Although high-speed profilers have been in use for long time as a tool to collect network-level IRI data for Pavement Management System (PMS) applications, however the use of this type of devices for project-level smoothness acceptance is relatively new. Therefore, NJDOT conducted a two-phase research study with the objectives of standardizing the testing protocols and identify/address the equipment related issues, such as repeatability, effects of testing speed and the use of high- and low- pass filters), manufacturers versus standard IRI computations (Proval and RoadRuf) and the impact of summary intervals.

Also, the study objectives included selecting a pavement profiling device as the Standard Pavement Profiler (SPP) for NJDOT, which will be used to calibrate other profilers, developing a procedure to calibrate and correlate other high speed profilers with NJDOT SPP and evaluating a standard software to process profile data and calculate IRI for NJDOT smoothness specifications. As a part of this study, detailed investigations were performed on the IRI algorithm and a new ride statistic was developed. Also, advanced profile analysis was performed to diagnose the profile characteristics that impact the rideability and user opinion. Comparisons were made between different ride statistics, traditional ride statistics (IRI, RN, PI and %DL) and the newly developed ride statistic.