Indicators of Longitudinal Road Unevenness and their Mutual Relationships

ABSTRACT An overview of contemporary indicators of longitudinal road unevenness (roughness) is given. The power spectral density (PSD) with its parameters (unevenness index and waviness), International Roughness Index (IRI), and three-band indicators (TBI) or triads are considered. Mutual conversion relations between the PSD and the remaining indicators are given. The importance of the waviness is emphasized and at the same time, it is shown that the estimation of waviness as an indispensable companion of each unevenness indicator is possible within the particular unevenness characterization and estimation methodology. For all the indicators considered, reference data on uncertainties are given, which have been obtained partly from own simulation studies, partly from data obtained from measurements on in-service roads.