Abstract
The rolling wheel deflectometer (RWD) and traffic speed deflectometer (TSD) are continuous deflection measuring devices used for structural evaluation of in-service pavements. Although recent studies have demonstrated the benefits of these devices, state agencies are inclined to believe that surface indices are generally sufficient to describe in-service pavement conditions (functional and structural conditions) and to make cost-effective maintenance and rehabilitation decisions. The main objective of this study was to assess whether the use of surface indices only or the declining rates of these indices to identify structurally damaged sections is feasible instead of relying on RWD and TSD estimated pavement structural indices. Results of the analysis showed that structural deficiency, rates of deterioration, and surface indices were correlated to a certain extent. These results were expected, as pavements that are structurally deteriorated will exhibit surface deficiencies over time. Yet, surface indices cannot be used as a reliable predictor of structural capacity. For RWD, the most accurate surface index, which was the alligator cracking surface index, erroneously identified 35% of structurally sound sections as structurally deficient and 51.5% of structurally deficient sections as structurally sound. Similar results were obtained for the TSD; in this case, the most accurate surface index, which was the random cracking index, erroneously identified 16.7% of structurally sound sections as structurally deficient and 51.0% of structurally deficient sections as structurally sound. The cost implication associated with misinterpreted sections from functional indices was investigated. The incorporation of structural indices is expected to provide significant savings to state agencies.
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