Typically, there is close relationship between the stiffness values measured with the Light Weight Deflectometer (LWD) and the field moisture content. The influence of moisture is much higher because of the capillary effect of water so the results are sensitive to insitu field moisture.

The optimum moisture from the Proctor Test will yield the best results, as one would expect. Every sand and gravel mixture has an optimum water content depending on grain size distribution.