International Roughness Index

About: International Roughness Index is a research topic. Over the lifetime, 942 publications have been published within this topic receiving 9444 citations.

Guidelines for conducting and calibrating road roughness measurements

Abstract: Road roughness is gaining increasing importance as an indicator of road condition, both in terms of pavement performance, and as a major determinant of road user costs. This paper defines roughness measurement systems hierachically into four groups, ranging from profilometric methods (2 groups), through response type road roughness measuring systems (RTRRMS's), and, subjective evaluation. The International Roughness Index (IRI) is defined, and the programs for it's calculation are provided. The IRI is based on simulation of the roughness response of a car travelling at 80 km/h. The report explains how all roughness measurements can be related to this scale, also when travelling at lower speeds than 80 km/h. The IRI emerges as a scale that can be used both for calibration and for comparative purposes.

On the calculation of international roughness index from longitudinal road profile

Abstract: The international roughness index (IRI) was established in 1986 by the World Bank and based on earlier work performed for NCHRP. IRI is calculated from a measured longitudinal road profile by accumulating the output from a quarter-car model and dividing by the profile length to yield a summary roughness index with units of slope. Although IRI is used widely, there is no single, short reference document that describes what it is and how it is calculated. Instead, the critical information is spread over several large reports. A short, self-contained reference that defines IRI is provided, along with all the information needed to compute it from longitudinal road profile measurements. The development of the IRI is reviewed, the mathematical definition is presented, an algorithm for calculating IRI is derived, the performance of the algorithm is analyzed, tested Fortran source code for computing IRI is presented, and problems with IRI (and profile measurement in general) that have emerged since 1986 are identified.

Applicability of the International Roughness Index as a Predictor of Asphalt Pavement Condition

Abstract: This note establishes the relationship between the surface distress of an asphalt pavement and its roughness, as conveyed respectively by the pavement condition index (PCI) and the international roughness index (IRI). The DataPave software provides the roughness of varied roadway pavement sections from the North Atlantic region that were investigated under the long term pavement performance (LTPP) study. The MicroPAVER1 software system computes the condition of the same sections using cross-referenced distress data from DataPave. A transformed linear regression model predicts pavement condition given roughness. It confirms the acceptability of the IRI as a, albeit not the sole, predictor variable of the PCI whereby the former accounts for the majority, close to 59%, of the variations in the latter. Further, an analysis of variance confirms the existence of a strong relationship between both variables.

Interpretation of road roughness profile data

Abstract: The majority of States own high-speed devices for measuring longitudinal road profiles that are potentially rich in information about the pavement surface condition. The primary objective of this research was to advance the state of practice for extracting this information. A secondary objective was to assist users in resolving common measurement errors. Vast amounts of measured profile data were acquired to evaluate various analysis methods in terms of their usefulness and validity when applied to profiles obtained from different types of instruments. Methods for determining an index called Rideability Number (RN) were studied in detail. A practical algorithm was developed for computing RN without bias from profiles obtained from a variety of equipment, with the exception of those that use ultrasonic sensors. Other analyses studied in the project include the International Roughness Index (IRI), power spectral density (PSD), high-pass filters, and cross correlation. The research was coordinated with activities of the Road Profiler User Group (RPUG). A critical problem facing road profiler users is a lack of knowledge involving the technology. Accordingly, a 2 1/2 day course on profile measurement and analysis was prepared, along with the first draft of a companion document called "The Little Book of Profiling". The course introduces new users to the basics of what profilers are, how they work, and what can be done with their data. A user-friendly profile analysis software package called RoadRuf was developed that includes many profile analysis methods. The software had been provided to participating States, and is available on the Internet.