Highway agencies routinely test and evaluate the condition of pavements to determine what, if any, maintenance or rehabilitation strategies are needed. The falling-weight deflectometer (FWD) is crucial to those monitoring activities. Data obtained from the FWD tell the highway agency how strong a pavement is, which is a key factor in evaluating pavement condition and performance and in designing new pavements or overlays.

But like all sophisticated tools, the FWD must be properly calibrated and used, or else the deflection measurements may be inaccurate and thus lead to
inappropriate remedies. To address this issue, the Strategic Highway Research Program and the Long Term Pavement Performance (LTPP) program devel-
oped a set of standardized FWD calibration procedures and also set up four regional FWD calibration centers.