Variability of Hamburg Wheel Tracking Devices (5-4977-01-1)

The objective of this implementation project was to prepare procurement specifications and purchase three Hamburg Wheel-Track Devices (HWTDs), install them in two different Texas Department of Transportation (TxDOT) laboratories, and provide training to assist the technicians in proper procedures for testing and data analysis. The implementation process included conducting a limited proficiency study of all five of the HWTDs belonging to TxDOT as well as two HWTDs belonging to the Texas Transportation Institute (TTI) and Pave Tex. The proficiency study determined the accuracy and precision of the seven HWTD devices. A statistical analysis of the results revealed no significant differences among the seven HWTDs. However, the ability of the statistical models to detect differences between the machines was restricted because of the low number of replications of the experiment. Observations indicate that it may be possible to improve the current TxDOT HWTD data collection technique to improve statistical validity of the measurements.