ABOUT THE RELATIONS BETWEEN THE STRUCTURE, TRAFFIC VARIOUS CAUSE OF THE EXPRESSWAY AND IRI

The objective of this study is to develop road surface control standards on expressways to provide driving comfort. This study focuses is placed on the IRI (International Roughness Index), a new index for road surface control, and its applicability. The questionnaire survey at 1999 provided certain correlation between the IRI and driving comfort.This paper shows a formula which represents time-based change in IRI using the aging of the road surface, based on the results of profile measurement on lanes for a combined length of 4200 km nationwide. We organized the relationship between road dimensions and the factors affecting the road surface, and identified road properties.