The first step in selecting the optimal rehabilitation strategy for any pavement is to identify the cause of the existing defects. In recent years nondestructive technologies such as Falling Weight Deflectometers and Ground Penetrating Radar have been used to evaluate subsurface conditions. However when used independently these technologies are not always adequate for identifying the cause of pavement deterioration. This paper will present the argument for developing an integrated approach to pavement evaluation wherein the high speed GPR survey results can be used to identify homogenous sections, locate potential subsurface defects and estimate layer thicknesses. The GPR then provides critical inputs to both the processing of the FWD data and the interpretation of the results.

In this paper a brief review will be presented on the principles of operation of both air launched and ground coupled GPR systems. Recently developed signal processing techniques for converting the GPR reflected waves into parameters of significance to highway engineers will be described. Five case studies from Texas and Finland will be included which demonstrate how both ground coupled and air launched GPR results can be effectively integrated with the FWD data to make project level decisions.