Continuous Deflection Testing of Highways at Traffic Speeds

Nondestructive testing devices have been utilized for the last 50 years to assess the structural condition and bearing capacity of existing or newly-constructed pavement systems. A variety of devices have been developed to measure the deformation (deflection) of a pavement due to an applied load. Currently, the most commonly-used nondestructive testing device is the Falling Weight Deflectometer. The Falling Weight Deflectometer is a stop and go (discrete testing) operation rather than a continuous testing operation. The discrete test points are assumed to be representative of a specified length of the pavement under investigation. The stop and go process increases testing time and operational cost and creates an unsafe working environment due to traffic interruptions. To measure deflection profiles at or near highway speeds, various national and international research efforts have taken place in the last decade. However, the status, reliability, operational speed and cost, and limitations of the developed systems are unknown. The main objective of this research project was to summarize the state-of-the-art of continuous deflection measurement systems. Another objective of this study was to propose a specification for an ideal device, if the existing devices do not meet the needs of the Texas Department of Transportation (TxDOT). The results of the findings and ways to incorporate that device in the TxDOT’s pavement management systems are reported here.