U.S. Department of Transportation
Federal Highway Administration
1200 New Jersey Avenue, SE
Washington, DC 20590
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
Data Source: U.S. Department of Transportation, Federal Highway Administration, Office of Highway Policy Information, Highway Performance Monitoring System.