TRR 1260 Pavement Design, Management And Performance, pp.125
Response-type road roughness measuring (RTRRM) systems have been widely used in United States and internationally in the evaluation of pavement surface roughness. One of the major problems associated with the calibration and operation of RTRRM systems has been the speed dependence of the systems. A reporting statistic from an RTRRM system has to be reported and qualified with speed operation before the statistic has a meaningful relationship with surface roughness. Because the frequency pass band of an RTRRM system is limited, the uotputs of the instruments are also affected by the frequencies of the surface profile. The Center for Transportation Reseach (CTR) of the University of Texas at Austin has been in the process of calibrating Highway Product International Automatic Road Analyzer (ARAN) unit for the Texas State Department of Highways and Public Transportation (SDHPT). During the process, a statistical model was developed to cancel the speed effect from the ARAN uotput. The methodology for generating this model can be applied to any of the various types of RTRRM instruments. The research effort concerning the model being conducted by CTR is introduced. The testing speed effect is analyzed by use of the transfer function of a simulation model of an RTRRM system i.e., the reference quarter-car simulation (RQCS)/. The amplitude-frequency characteristics of the vehicle axle's vertical acceleration due to changing profile elevations are obtained. In order to quantitatively see the effect of the testing speed on the RTRRM system, it was necessary to simulate the RQCS by the digital difference equation approach with a sine function as the simulation input. A speed effect cnceling model unit was generated, and also applied to the ARAN unit. The resulting model will be used to standardize the roughness outputs of the RTRRM system and eliminate the operational speed effect from the output statistics. The methodology is expleined and can be applied to other types of RTRRM instruments.