Geophysical methods provide a means to rapidly and economically characterize subsurface conditions and infer soil properties over a spatial extent that is not possible with conventional methods.

The TRB National Cooperative Highway Research Program's NCHRP Synthesis 547: Advancements in Use of Geophysical Methods for Transportation Projects evaluates the current state of practice in the use of geophysical methods by state transportation agencies.

Challenges and obstacles remain that must be overcome if routine implementation of geophysical methods for transportation projects is to be realized. Uncertainties associated with insufficient or poor site characterization can lead to overly conservative designs, increased risk of poor performance, cost increases attributable to changed conditions, and project delays.