Study of the Structural Performance of Flexible Pavements Using a Traffic Speed Deflectometer

The Falling Weight Deflectometer (FWD) is a non-destructive testing device which has been used by many road agencies worldwide since 1980 for structural evaluation of flexible pavements. In early 2000, the world first Doppler based Traffic Speed Deflectometer (TSD) was developed by Greenwood Engineering and now eight TSD vehicles are in use worldwide. The two main advantages of the TSD technology are; it's ability to carry out continuous bearing capacity measurements rather than at discrete points and that testing can be carried out at traffic speed without the need for lane closures such as with a stationary device such as the FWD. The objective of this paper is to study the structural performance of flexible pavements using TSD. This study draws some interesting findings in that deflection data collected by TSD can be transformed to FWD equivalent Structural Numbers with a simple model as derived in the study. The study has also successfully established correlation between maximum deflections TSD-D-0 and FWD-D-0 that are derived from the two devices.