Specification of Obstacles in the Longitudinal Road Profile by Median Filtering

Abstract

Separation of large obstacles from longitudinal road profiles using median filtering is presented. Detailed testing of this method confirms its ability to remove large obstacles without corrupting the random component of the road profile. At the same time, optimal length of the window as the ceiling of double the maximum obstacle length is estimated. For the specification of individual obstacles, six indicators are introduced, namely, obstacle length, maximum obstacle height, ratio of obstacle length to its maximum height, area of the obstacle profile, obstacle volume, and distance between two successive obstacles. About 23,400 records of road profiles gathered from the Long Term Pavement Performance (LTPP) program were processed from which 5,036 profiles displayed obstacles higher than 0.3 cm. A total number of 16,590 obstacles were detected. Statistical processing of all of these profiles to distinguish between asphalt concrete (AC) and portland cement concrete (CC) road surfaces and between bumps (B) and potholes (P) identified that 71% of all obstacles belong to the AC+P combination. In the appendix, correction factors (CF) are presented, allowing the elimination of bias attributable to preprocessing operations applied on LTPP profile records used for estimation of true obstacle dimensions.