Development and Initial Testing of the Total Pavement Acceptance Device (TPAD)

A new, multi-function pavement testing device has been developed by a joint effort between the Texas Department of Transportation (TxDOT), the Center for Transportation Research (CTR) at the University of Texas at Austin (UT) and the Texas Transportation Institute (TTI) at Texas A&M University. This new device is called the Total Pavement Acceptance Device (TPAD). The objective of TPAD testing is to nondestructively and nonintrusively investigate the total pavement’s structural adequacy. The multiple functions of the TPAD presently include the following measurement capabilities: (1) rolling dynamic deflectometer (RDD), (2) ground penetrating radar (GPR), (3) global positioning system (GPS), (4) pavement surface temperature, (5) digital video imaging of pavement and right-of-way conditions, and (6) longitudinal survey offsets through a distance measurement instrument (DMI). The TPAD is designed to perform continuous measurements at speeds around 3.2 to 4.8 km/hr (2 to 3 mph), with increased speeds planned in future developments. The main developmental efforts have focused on developing: (1) a moving platform with precise speed control in the range of 0.8 to 16 km/hr (0.5 to 10 mph), (2) automated RDD pavement loading and deflection sensing systems, (3) an improved analysis scheme for processing RDD deflection data on the fly over incremental distances of 6 to 30 cm (0.2 to 1 ft) and (4) a new data collection system that integrates the results from all measurement functions and displays them in real time. Descriptions of the equipment and example sets of continuous RDD pavement deflections and GPR evaluations are presented.