Analysis of flexible pavement design standards based on the Structural Number (SN) in Florida and Arizona (United States) and recommendations for improvement TCCS 37:2022

The technical specification TCCS 37:2022 provides guidelines for flexible pavement design based on the Structural Number (SN) concept, developed from the AASHTO 1993 methodology. However, in the context of increasing heavy truck traffic and more demanding service requirements, this specification exhibits several limitations, particularly in terms of standardization, structural configuration control, and its linkage with material properties. This study conducts a comparative analysis of two U.S. pavement design standards, namely the Flexible Pavement Design Manual FDOT FDP, 2026) issued by the Florida Department of Transportation (Florida DOT) and the Pavement Design Manual (ADOT FPD, 2017) issued by the Arizona Department of Transportation (Arizona DOT). The analysis focuses on the SN-based design framework, input parameters, layer coefficients, structural design rules, base grouping mechanisms, and the influence of drainage conditions. The results indicate that FDOT FDP adopts a predominantly tabulated approach with an emphasis on minimum structural control, whereas ADOT FDP maintains a comprehensive mechanistic–empirical framework and establishes a stronger linkage between layer coefficients and material properties. Based on these findings, the study identifies key limitations of TCCS 37:2022 and proposes directions for improvement to support its development into a national standard (TCVN)