Influence of Profile Specification on International Roughness Index

Abstract

This paper addressed an important question of selection of wheel path(s) for International Roughness Index (IRI) or Mean Roughness Index (MRI) estimation. Twenty-one IRI/MRI alternatives of wheel path position(s) (single path and two parallel paths) were estimated. Sixteen parallel records of longitudinal profiles and a road network with a total length of approximately 12,000 km were processed. The correlation between simulated vehicle vibration response and IRI/MRI alternatives was evaluated. Vibration response was calculated on a passenger full-car model. The influence of vibration response category (ride comfort and vehicle controllability and safety), road category (motorways, first-class roads, and second-class roads), and report interval of IRI (20 and 100 m) on the results was analyzed. The best correlation was established for parallel profiles that were in the lateral distance of 15–30 cm of vehicle excitation profiles. A stronger correlation was identified for single path near the right (outer) wheel path for motorways. A weaker correlation was identified for the left (inner) wheel path or two parallel profiles localized further than 30 cm from excitation profiles. The same correlation coefficients were calculated for most of the IRI/MRI alternatives and the 100-m report interval of IRI.