Exploratory Study to Use Traffic Speed Deflectometers (TSD) for Project-Level Pavement Evaluations

ARRB Group has purchased a second-generation Greenwood Engineering Traffic Speed Deflectometer (TSD) and commenced data collection across Australasia in 2014. The TSD, fitted with extra ARRB Hawkeye equipment, can collect continuous deflection profile and surface condition data (such as cracking, rutting, roughness and surface images) at traffic speeds of around 80 km/h. While the TSD is traditionally seen as a network-level pavement evaluation tool, this paper presents an exploratory study of using the device for project-level pavement evaluation. Using linear-elastic mechanistic analysis software, theoretical surface basins were computed and compared with the TSD-measured deflection basins. This provides an insight into ways in which TSD results could be interpreted and utilised in routine pavement engineering. Limited theoretical models of TSD loading on a range of pavement profiles have been computed. Back-calculation software, EFROMD3, was used to highlight the promising potential to estimate in situ layer moduli via back-calculating from the TSD-measured deflection basins. Recommended future research is presented.