Updating perpetual pavement design criteria: from legacy practices to strain ratio-based methodologies

In recent years, the importance of having cost-effective and environmentally sustainable infrastructure has grown, and pavements are not an exception. Within this framework, perpetual pavements have emerged as a valid alternative, with their advantages and limitations, seeking to achieve perpetual pavements that require occasional maintenance work over long periods of time. This document will include a compilation of some international studies based on perpetual pavement design and will present, among others, the resistance limits used in those methodologies. In addition, an international project of flexible pavement structure that was originally developed using the perpetual pavement design principles introduced in a 2007 study, will be analyzed. While considered innovative at the time, the approach relied on a fixed tensile strain limit at the bottom of the asphalt layers and did not take subgrade rutting into account as part of the structural design process-assumptions that are now outdated according to current international practices. This study will re-examine the original design using the updated mechanistic-empirical methodology outlined in Perpetual Pavements: A Manual of Practice. The revised framework introduces bottom-up fatigue analysis based on strain ratio criteria and explicitly incorporates permanent deformation in the subgrade as a key design consideration. A comparative assessment will be carried out to explore how the structural configuration changes when applying modern endurance thresholds and performance-based design parameters. The objective of this re-evaluation is to support the development of more resilient and technically sound perpetual pavement solutions, aligned with current best international practices in long-life asphalt pavement design.