International Roughness Index (IRI)

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International Roughness Index (IRI)

The International Roughness Index is used to evaluate road pavement. It indicates how irregularities in the pavement affect the ride quality of a vehicle. IRI values are calculated by simulating the response of an idealized car to the road profile. When irregularities in the road are encountered, the wheel of the car will be given upwards or downwards momentum and the car will be given a slightly different momentum due to the dampening effects of the car’s suspension. The IRI is a measure of the momentum of the car and is reported in inches/mile or meters/kilometer. Smaller values represent smoother rides.

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