Improving traffic characterization to enhance pavement design and performance

One of the latest efforts aimed at revolutionizing the pavement design and analysis procedures is the National Cooperative for Highway Research Program (NCHRP) Project 1-37A (Development of the 2002 Guide for the Design of New and Rehabilitated Pavement Structures). One significant aspect of this development is the employment of truck axle load spectra rather than ESALs. Moreover, the team responsible for NCHRP Project 1-39 (Traffic Data for Mechanistic Pavement Design), which is a complementary project to NCHRP 1-37A, was also interested in determining whether collecting more accurate tire pressure distributions is critical for the 2002 Design Guide or not. However, efforts aimed at simplifying this complex new design process resulted in its deferral by the NCHRP 1-37A team.; The first objective of this research is the development of truck axle load spectra for Washington State. Axle load data collected at WIM stations will be utilized. The load spectra will encompass the principal truck axles: single, tandem, and tridem axles. Achieving this objective will afford the Washington State Department of Transportation (WSDOT) the opportunity to accommodate the requirements of the 2002 Design Guide. SHAs that decide against using the 2002 Design Guide may choose to employ the load spectra produced ESALs instead.; The second objective is the exploration of strain distributions and intensities associated with tire prints with non-uniformly distributed stresses (NDS) versus uniformly distributed stresses (UDS) throughout the asphalt layer of flexible pavements, utilizing the finite element software EverFlex. Achieving this objective will increase the understanding of strains that exist throughout the wearing course and will verify, to some extent, whether or not more precise tire pressures are needed for more practical pavement design procedures.; Attaining the research objectives will aid the understating of and need for load spectra in future pavement design procedures. Secondly, the conclusions will also prove or disprove the necessity for better-defined contact stress distribution at the tire-pavement interface for the realization of more realistic pavement design procedures. The research objectives are stepping-stones in the quest for a more complete pavement design, which commences with verifying its necessary traffic data.