In 1999, $5.5 billion in Federal highway funds were spent on pavement rehabilitation and resurfacing. To make the best possible decisions about where and when to conduct pavement rehabilitation work, State departments of transportation (DOTs) need extensive data on the structural condition of pavement.

To measure the structural condition of pavement, most pavement engineers rely on falling-weight deflectometer (FWD) technology. FWDs "thump" the pavement and record information about its structure and integrity. But like all sophisticated tools, the FWD must be properly calibrated. If it is not, measurements will be inaccurate. Inaccuracy wastes precious budget dollars