This guide summarized the layer material type and thickness data structure in the Long-Term Pavement Performance (LTPP) database. Summaries of layer thickness within-section data variablility and constructed thickness deviations from the target thickness are also provided for LTPP sections; the guide provides several benchmark values for both of these data elements for different material types. Guidelines are also presented to search for the most appropriate thickness information for different research purposes.

This guide will be of interest to highway agency engineers and reearchers involved in pavement design, performance modeling, and construction quality assurance.