Incorporating Traffic Speed Deflection Devices in Structural Evaluation of Flexible Pavement

Abstract

Pavement management systems of highway agencies in the various states are primarily based on surface condition data. Surface cracking is used as the main indicator of pavement structural condition. However, with effective pavement treatment that intervenes early to preserve and extend the life of pavements and increasingly thicker long-life pavements, surface cracks no longer tell the true structural condition, or health, of the pavement structure. In addition, surface cracks lack an indicator of pavement deterioration. Knowledge of the true pavement structural condition and the rate of deterioration is needed not only for planning of optimal structural rehabilitation activities and future budget needs but also for implementing a performance-based federal-aid program. This paper presents a methodology for interpreting measurements from traffic speed deflection devices (TSDDs) to track flexible pavement structural condition over time and for assessing rehabilitation needs at a network level to address both structural adequacy and surface condition. The paper also demonstrates a methodology for interpreting TSDD measurements to estimate remaining pavement structural capacity. Curvature indexes measured from TSDD were found to be reasonable estimators of pavement structural condition and were used in the demonstration. Horizontal tensile strain, a primary initiator of fatigue damage and cracking, can be estimated from periodic TSDD measurements and used as a leading indicator of pavement deterioration and structural performance. Any differences in pavement structural performance arising from the pavement's as-designed versus as-constructed state and its assumed versus actual traffic and climate effects can be assessed and future treatments modified as necessary.