Development of Second-Generation Rolling Sensor for Increased RDD Testing Speed

The primary objective of this paper is to present the development of the second-generation RDD rolling sensor. This sensor increases the RDD testing speed from 1 to 3 mph (1.6 to 4.8 km/hr). The two key factors that limit the existing testing speed are: (1) the negative acceleration of the rolling sensor as it moves along a rough surface, and (2) the level of rolling noise measured during testing. Two improvements to the existing rolling sensor design were made to address the above two issues. First, an additional hold-down force was provided to each rolling sensor. The allowable negative vertical acceleration was increased by the addition of a hold-down force on each sensor. Second, the diameter of the rolling wheels was also increased. Finally, field trials using the second-generation rolling sensors at different test speeds along the TxAPT test facility were carried out. It was found that the deflection profiles collected are comparable when collected at 1, 2 and 3 mph.