Road users’ perception of roughness and the corresponding IRI threshold values

Abstract

One of the primary objectives of highway agencies in Canada is providing a safe and reliable road network with a good level of service. In the Province of Alberta specific International Roughness Index (IRI) threshold values classify pavements into good, fair, and poor condition categories to manage and schedule rehabilitation and maintenance programs. This research investigated the significant factors that affect the perception of road roughness and established IRI threshold values for good, fair, and poor road condition based on public perception. A questionnaire was designed to investigate the road users’ perception and included questions covering gender, age, familiarity with the road, type and model of car, and perception of road roughness. In addition, psychometric scaling analysis was used to develop a set of IRI threshold values for classifying road condition based on public perception in the Province of Alberta. According to the results of the survey, Alberta Transportation threshold values of IRI do not agree with the road users’ opinion and an alternate set of threshold values was developed. The analysis of the survey results identified that trip purpose, driving experience, dry surface, and familiarity with the road are the most significant factors that influence the perception of road roughness.