Austroads Road Deterioration Model Update: Deflection

This report documents a project designed to update the current Austroads road deterioration (RD) models using the long-term pavement performance and long-term pavement performance maintenance (LTPP/LTPPM) dataset and other data available, such as the traffic speed deflectometer (TSD) datasets, to improve these models' explanatory power. A proof-of-concept approach based on using the available TSD datasets was undertaken early in the project which determined that these datasets were not appropriate at this stage for developing a refined structural RD model. Development of a structural RD model was therefore based on the extensive time series captured by the LTPP/LTPPM datasets to produce a single structural RD model for flexible sprayed sealed pavements. The structural RD model was based on a mechanistic‑empirical deterministic approach using a multi-variate non‑linear regression (MVNLR) analysis. Seasonal correction of the measured maximum deflection proved to be problematic using measures of the lower soil moisture content, so the corrections were made using the current Austroads approach to seasonal variation. The report is available from Austroads at https://austroads.com.au/publications/pavement/ap-t367-23