Is the Road Quality Still Better

AbstractThis study quantifies and explains the paradox of a slow increase in road quality over time with a concomitant decrease in ride comfort or objective road quality. The study estimates the effect of road profile wavelength contents on the International Roughness Index (IRI) and planar personal half-car model vertical vibration response. Two cases are examined: (a) decrease in short-wave amplitudes ( 20  m). The wavelength-content change was modulated by a change in the road profile spectrum slope (i.e., waviness) in both analyzed wavebands. The results indicate a relative insensitivity of the IRI algorithm to a change in road quality in both cases, while the particular vibration responses (dynamic tire force, seat or car body vertical acceleration) are markedly changed. It is shown that the IRI algorithm calculated for the alternative velocities should be a more robust tool to detect the change in wavelength contents in the examined wavebands.