International Roughness Index
英[ˌɪntəˈnæʃənəl ˈrʌfnɪs ˈindeks]美[ˌɪntɚˈnæʃənəl ˈrʌfnɪs ˈɪnˌdɛks]
The International Roughness Index (IRI) is the roughness index most commonly obtained from measured longitudinal road profiles. It is calculated using a quarter-car vehicle math model, whose response is accumulated to yield a roughness index with units of slope (in/mi, m/km, etc.