Pavement roughness index measurements with a 3D line laser

This paper describes the longitudinal layout and working principle of a 3D line laser profilometer with a moving reference algorithm based on the line laser design which can continuously measure the longitudinal contour of a track plane at 20~100 km/h. The device is placed on the left and right wheel track belts. The line laser survey path is 270 mm long and the vertical accuracy is 0.01 mm. The system was used to measure two sections of different quality asphalt pavement contours over distances of 10 m and 100 m to determine the international roughness index (IRI) for each section. The results show that the IRI at various speeds had a relative measurement error less than 3%. At low speeds, the left and right contour graph standard deviations were less than 0.3 and less than 0.6 at higher variable speeds. Measurements using a digital test vehicle gave poor results for quick starts with distorted data over the first 50 m. Thus, the initial values for the standard gold car model were taken from the first quarter of the dynamic response model results as the initial value. For the right contour graph, 91.4% of the data had coefficients of variation less than 5% and 8.6% of the coefficients of variation were less than 15%. For the left contour graph, 94.2% of the coefficients of variation were less than 5% and 5.8% of the coefficients of variation were less than 10%. The IRI results at sites 1 and 2 were in line with the actual service conditions of the road surfaces. The evaluations show that this dynamic monitoring system can accurately measure the IRI at both low speeds and variable speeds. This system can be used for pavement flatness surveys and pavement service status assessments. © 2021, Tsinghua University Press. All right reserved.