International Roughness Index (IRI) means a statistic used to estimate the amount of roughness in a measured longitudinal profile. The IRI is computed from a single longitudinal profile using a quarter-car simulation, as described in the report: On the Calculation of IRI from Longitudinal Road Profile (Sayers, M.W., Transportation Research Board 1501, Transportation Research Board, Washington, DC 1995).


23 CFR § 490.305

Scoping language

The following definitions are only applicable to this subpart, unless otherwise provided:

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