Nondestructive pavement testing devices produce and collect deflection data using methods unique to each device. Loadings are produced on various-sized loaded areas by vibratory motions of various loads and frequencies and also by dropping masses from various heights. Deflections are measured using various types of deflection sensors.
Data from three vibratory loading and four falling weight loading nondestructive pavement testing devices are evaluated and compared for accuracy, reliability, and repeatability. The loading output of each device is compared to the output of a load cell placed under the loaded area. The output of the deflection gauges at varied load levels is compared to the output from both a linear variable differential transformer placed under the gauge and a transducer placed next to the gauge. The repeatability of each device to produce consistent and accurate data at one location on various pavement types is determined by loading that location many times in a short period of time. The long-term repeatability of each device is determined by loading a specific location many times over a long period of time. Conclusions are drawn for each device concerning its reliability for producing accurate loading and deflection output and its repeatability for producing accurate results over time.