Definition
Surface Distress Index (RT-SDI). A 0-100 score built on the FHWA Surface Distress Index methodology with weighted category scoring. Focuses on surface-level deterioration: raveling, bleeding, weathering, and oxidation. Complements PCI by distinguishing surface maintenance needs from structural issues. Applied to both asphalt and concrete.
In context
An agency can use SDI to flag surface maintenance needs without waiting for the structural score to drop.