The analysis of road roughness and the perception of road roughness

Roughness is found by analysing the longitudinal profile of a road and is a summary of the characteristics of the road surface that impact on the ride of a passenger in a car. Since heavy vehicles respond differently to different wavelength bands of roughness, IRI may not be applicable for trucks. A system of analysis is proposed using power spectral density (PSD) of the profile. This provides a measure of the level of development of roughness contained in various wavebands in the pavement. Certain wavebands have been tentatively identified as contributing to the resonance of airbag and steel suspensions. PSD analysis is used to identify the level of wavebands and thus indicate whether road users may determine if the road is rough. A particular section of a Highway in the state of Victoria, Australia, was identified as rough by objective measurement and subjective opinion. The wavebands that affect the performance of heavy vehicles were identified and recognised in the section of the highway chosen for analysis. A simulation of the passage of an articulated heavy vehicle showed that the dynamic wheel load exceeded the static wheel load by a factor of up to two. A link is established between the roughness of a section of pavement, the perception of the section as being rough, and the dynamic wheel loads induced in the pavement by interaction of the suspension system with the surface profile. PSD plots have a potential of providing an analysis technique that can identify roughness with more precision than the IRI or NAASRA assessment method