This report is a comprehensive review and evaluation of the Long-Term Pavement Performance (LTPP) backcalculation data. In this study, a new approach, called forwardcalculation was developed to determine layered elastic moduli from in situ load-deflection data with procedures and results documented.  The entire set of LTPP-computed parameters of backcalculation results was screened using forwardcalculated moduli.

This report will interest highway agency engineers involved in pavement analysis, design, construction, and deflection data collection, as well as researchers who use LTPP load-deflection data to improve design procedures and standards for constructing and rehabilitating pavements.