Our Nation's Highways: 2008

Figure 7-2. Pavement Surface Smoothness: Rural and Urban Interstate, 2006

The International Roughness Index (IRI) is one of the most widely used measures of the quality of ride smoothness. Pavements with an IRI rating of less than 170 are considered to have an acceptable ride quality, while those with an IRI of less than 95 can be considered to have a good or very good ride quality.

Data represented in the inset chart
Table in Excel format

Data Source: U.S. Department of Transportation, Federal Highway Administration, Office of Highway Policy Information, Highway Performance Monitoring System.