PM2 - Bridge
Updated Using 2022 Data

The second of the performance measures rules (PM2) issued by the Federal Highway Administration (FHWA) establishes two measures to assess the condition of bridges on the National Highway System (NHS):

  1. Percentage of NHS bridges by deck area in Good condition
  2. Percentage of NHS bridges by deck area in Poor condition

Good condition suggests that no major investment is needed, while Poor condition suggests that major investment is needed to improve the pavement condition.

FDOT established statewide two and four-year targets in coordination with the state’s MPOs, to the extent practicable, for each FHWA bridge performance measure. All 27 MPOs support the statewide targets including the intent to plan and program projects that are anticipated to support progress toward achieving the targets.

Methodology

Methodology: PM2 - Bridge

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

Metric rating Good Fair Poor
Deck
(Item 58) 		≥ 7 5 of 6 ≤ 4
Superstructure
(Item 59) 		≥ 7 5 or 6
 ≤ 4
Substructure
(Item 60) 		≥ 7 5 or 6 ≤ 4
Culvert
(Item 62) 		≥ 7 5 or 6 ≤ 4

Calculation

`"% of NHS bridges by deck area in Good condition ​" = ("∑"_(g=1)^(GOOD)"[Length * Width]"_("Bridge g"))/("∑"_(s=1)^(TOTAL)"[Length * Width]"_("Bridge s"))`​​ `"% of NHS bridges by deck area in Poor condition ​" = ("∑"_(p=1)^(POOR)"[Length * Width]"_("Bridge p"))/("∑"_(s=1)^(TOTAL)"[Length * Width]"_("Bridge s"))`​​

Where,

LengthStructure length (NBI data item 49)
WidthBridge deck width (NBI data item 52)
gBridges in good condition
pBridges in poor condition
sBridges on NHS
Definitions

Definitions: PM2 - Bridge

  • 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.
Download Data

For information on state bridge measures, please click here.

Date of last refresh: 12/22/2023

SOURCE

FDOT Office of Maintenance