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International Roughness Index (IRI)
We have delivered IRI tests for more than 2,500 kilometers
International Roughness Index (IRI) is widely used as a performance indicator to assess the roughness or smoothness of road surfaces. By analyzing longitudinal road profiles, IRI quantifies the vertical deviations or bumps experienced by vehicles as they travel along the road. This information helps evaluate the overall condition of road surfaces and identify sections that require maintenance or rehabilitation.
The IRI emerged in 1986 as a pioneering method to quantify road roughness. Developed by the World Bank and International Road Federation (IRF), it quickly gained global recognition for its standardized approach. Unlike the Pavement Condition Index (PCI), which assesses distresses and surface condition, the IRI focuses solely on measuring longitudinal road profiles.
Together, the IRI and PCI offer complementary perspectives on pavement condition.
The IRI stands out from other pavement performance indicators due to its reduced subjectivity and stochasticity. It calculates roughness on a per wheelpath basis, offering a more detailed assessment. In comparison, the PCI considers various distresses and surface conditions, encompassing a broader range of pavement conditions. It evaluates distress severity and extent, providing a comprehensive overview of the pavement condition.
Purposes and uses of IRI
Pavement Performance Evaluation: IRI serves as a valuable tool for evaluating the performance of pavements over time. By monitoring changes in IRI values, transportation agencies can track the deterioration or improvement of road conditions. IRI data enables them to prioritize maintenance activities, assess the effectiveness of rehabilitation strategies, and make informed decisions about infrastructure investments.
Quality Control during Construction: IRI measurements can be used as a quality control tool during pavement construction. By comparing the achieved IRI values with specified thresholds or target levels, construction teams can assess whether the constructed pavement meets the desired smoothness requirements. This helps ensure that new pavements meet quality standards and deliver a comfortable ride for road users.
Road Network Management: IRI is a widely accepted roughness index used for managing road networks. By regularly collecting IRI data across a road system, agencies can establish a comprehensive database of road roughness information. This data assists in prioritizing maintenance and rehabilitation projects, allocating resources effectively, and developing long-term road network management plans.
Performance Monitoring and Benchmarking: IRI allows for performance monitoring and benchmarking across different road sections, regions, or countries. By comparing IRI values, transportation agencies can identify areas of concern, benchmark against industry standards, and implement best practices to improve road conditions. This promotes knowledge sharing, collaboration, and continuous improvement in road infrastructure management.
Objective and Standardized Assessment: IRI provides an objective and standardized measure of road roughness, reducing subjectivity and variability compared to other pavement performance indicators like the Pavement Condition Index (PCI). This makes IRI a widely accepted and consistent roughness index for international comparisons, research studies, and policy development.