Robust Deflection Indices from Traffic-Speed Deflectometer Measurements to Predict Critical Pavement Responses for Network-Level Pavement Management System Application

Traffic-speed deflectometers (TSD) are used in several countries to evaluate the pavement structural condition at the network level. Fatigue and rutting strains are commonly used as pavement critical responses in mechanistic-empirical design procedures to predict pavement structural performance. For successful pavement management system (PMS) application, robust indices that can be readily computed from TSD measurements and best related to the pavement critical responses should be identified. In this study, a comprehensive sensitivity analysis on deflection basin indices and their correlations with fatigue and rutting strains is performed using a range of pavement structures. A commercially available program was used in the first part of the study to compute dynamic deflection basins and evaluate the effects of material properties and vehicle speed on the indices. The indices that best relate to critical responses were identified from the software analyses and subsequently evaluated with a wider range of pavement structures analyzed using a layered linear-elastic program. Results from the TSD accuracy field evaluation were then used to further identify the robust indices in light of measurement accuracy. The study found that classifying pavement structures based on asphalt concrete (AC) thickness would be an appropriate selection for network-level PMS applications. Evaluation of 67 deflection basin indices showed that deflection slope indices ${\mathrm{DSI}}_{200–300}$ ($D_{200}–D_{300}$) and ${\mathrm{DSI}}_{300–900}$ ($D_{300}–D_{900}$) were well related indices with fatigue and rutting strains, respectively, and were selected to establish relationships with critical pavement responses for pavement categories based on AC layer thickness.