This study provides recommendations for using the Road Rater Model 400B and the PEDMOD (Pavement Evaluation and Design Model) program for pavement evaluation and design. In order to address seasonal variation in pavement response for pavement evaluation and design, thirty-six test sections were established in eight counties in Washington State. Road Rater deflection data was collected monthly on the test sections for a period of one year.
The pavement evaluation and design capabilities in the PEDMOD program utilize resilient material properties obtained from WESDEF, a backcalculation analysis program developed at the U.S. Army Corps of Engineers Waterways Experiment Station, which is contained within the PEDMOD program. Results obtained from WESDEF using Road Rater deflection data collected on the test sections indicate that it is difficult to obtain meaningful resilient material properties for pavement layer materials. Results of the analysis of deflection data for seasonal variability indicate that some general trends in variation in maximum deflection and subgrade resilient modulus occurred during the 12- month testing period, however, the test sections should be maintained for a longer period of time to develop specific seasonal correction factors. Recommendations are provided for calibrating the Road Rater and performing systemwide and design level deflection testing as well as recommendations for the use of PEDMOD. In addition, recommendations are provided for alternative techniques for pavement evaluation using parameters obtained directly from Road Rater deflection basins.