Details of the second performance rule (PM2) are available here.

The bridge performance measures refer to the percentages of deck area classified as in Good or Poor condition, computed using National Bridge Inventory (NBI) condition rating metrics for Deck, Superstructure, Substructure, and Culvert. The bridge condition is determined by the lowest rating of the metrics. If the lowest rating is greater than or equal to 7, the bridge is classified as Good; if it is less than or equal to 4, the bridge is classified as Poor. Bridges rated below 7 but above 4 will be classified as Fair; however, States are not required to report FAIR condition.

Thresholds for Pavement Performance Metrics

• NBI Data Item 49: Structure Length represents the length of roadway which is supported on the bridge structure. The length should be measured back-to-back of backwalls of abutments or from paving notch to paving notch.
• NBI Data Item 52: Deck Width represents the out-to-out width of the bridge deck structure.
• NBI Data Item 58: Deck describes the overall condition rating of the deck.
• NBI Data Item 59: Superstructure describes the physical condition of all structural members.
• NBI Data Item 60: Substructure describes the physical condition of piers, abutments, piles, fenders, footings, or other components. The substructure condition rating shall be made independent of the deck and superstructure.
• NBI Data Item 62: Culvert evaluates the alignment, settlement, joints, structural condition, scour, and other items associated with culverts.