Evaluation of road surface profiler and transverse profilograph for determination of rut depths

In recent years, the road surface profiler (RSP), also known as the high-speed profiler, has been used as the standard equipment for measurement of rut depths. Typically, for highway pavements an RSP with a three-sensor configuration is used to measure rut depth. Rut-depth measurements were taken with an RSP with three sensors at a spacing of 0.87 m and with a transverse profilograph (TP) on six projects, each of which was approximately 8 km (5 mi) long. At any given location the rut depth taken with the RSP was, on average, three times less than that taken with the TP. Different values of rut depth were determined by simulating the lateral movement of the vehicle, effectively, vehicle wander. Comparison of the rut-depth measurements obtained with the actual RSP and those obtained with the simulated RSP showed that the RSP vehicle had wandered from the center in almost all cases and that the wander in some cases was up to 0.57 m. The distance between the maximum rut depths within each wheel-path varied from 1.55 to 2.19 m, with an average of 1.86 m. The measured rut depth increased by as much as 300 percent when the sensor spacing was varied from 0.75 to 1.20 m. Measurement of the transverse profile was determined to be the most accurate method of rut-depth measurement. It will be possible to accomplish this either with additional sensors required to capture the transverse profile hi the RSP or with a TP.