Virginia US-460 Traffic Speed Deflectometer (TSD) Historical Structural Data Comparison in 2017 and 2022

When evaluating pavement design and rehabilitation techniques, the importance of structural data for pavement performance modeling is widely recognized. For example, surface deflection measurements are used to determine the elastic moduli of the pavement layers and estimate the pavement remaining structural life. In the last 10 years, traffic speed deflectometer devices (TSDDs) have become recognized as the future of pavement deflection data collection. This is primarily due to their ability to collect continuous deflection data at traffic speeds, in contrast to the traditional falling weight deflectometer (FWD) systems, which have relatively low productivity rate, require traffic control, and have safety concerns for the operator and the traveling public. On this basis, the Virginia DOT has been pursuing research related to TSDDs for the past seven years. In 2017, deflection data were collected on a large portion of its pavement network using a TSDD. A rural primary four-lane divided route (US-460) was part of the collection in 2017, and one section of this road was also collected in 2022. This paper focuses on comparing the data collected in 2017 to the data collected in 2022. The required asphalt overlay thickness was also assessed using AASHTO-93 methodology. The results showed thicker asphalt overlay thickness required in 2022 compared to 2017. Some unexpected results were observed when comparing 2022 and 2017 measures deflection velocities, and vertical deflection.