Smoothness Indices

The following are the smoothness indices currently used in the United States. Please note that while some states do not have specific smoothness specifications per se, virtually all states have some form of straightedge requirement for paving operations.

• IRI: International Roughness Index
• MRI: Mean Roughness Index
• HRI: Half-car Roughness Index
• PrI: Profilograph Index
• RN: Ride Number (used in Florida and New Hampshire HMA specifications only)
• MRN: Mays Ride Number (used in Arizona and South Carolina specifications only)
• CSI: Cumulative Straightedge Index (used in North Carolina HMA specification only)
• RQI: Ride Quality Index (used in Michigan specifications only)