About the National Bridge Inventory (NBI)

History of the NBI

The National Bridge Inventory (NBI) is a database that is compiled by the Federal Highway Administration (FHWA). In includes information on all bridges and tunnels in the United States that have roads passing above or below them. Note that pedestrian bridges, railroad bridges and bridges less than 20 feet long are not included.

The first bridge oversite organization was the U.S. Office of Road Inquiry, which was established in the Agriculture Department in 1893. This was reestablished as the Division of Highway Bridges and Culverts in 1910, in order to assist State and local officials in bridge design and construction. This agency published the first version of the Typical Specifications for the Fabrication and Erection of Steel Highway Bridges in 1910.

The National Transportation Safety Board and the U.S. Department of Transportation were formed on April 1, 1967. Both agencies were involved in the investigation of the Silver Bridge collapse, which occurred on December 15, 1967. This bridge carried U.S. 35 over the Ohio River, between Point Pleasant, WV, and Gallipolis, OH. It collapsed during rush hour, resulting in the deaths of 46 people. The cause of the collapse was an instantaneous fracture of a single eye-bar in a suspension chain, due to a small defect 0.1 inches deep. After this collapse, a section on "Bridge Inspection" was included in the Federal-Aid Highway Act of 1968. This section called for the Secretary of Transportation to work with knowledgeable organizations to “establish national bridge inspection standards in order to provide for the proper safety inspection of bridges on any of the Federal-aid highway systems." These standards were to detail the methods for inspections, the maximum time between inspections, and the qualifications of those doing the inspections.

The National Bridge Inventory Specifications (NBIS) were published on April 27, 1971. They specified that bridges had to be inspected every two years. The State were to prepare written reports on the inspection findings, including any needed follow-up actions. The FHWA uses the results of the inspections to create the National Bridge Inventory to track the performance of highway bridge.

Since it’s publication in 1971, the NBIS has only had four significant changes. The first change occurred in 1979, when the scope was expanded. The original standards bridges on the Federal-aid highway systems, and the standards were updated to include all all bridges on public roads. The NBIS was updated again in 1988 to include requirements or inspection of fracture critical bridges and bridges needing underwater inspection. In 1933, requirements were added for reports on follow-up correction actions taken in response to critical findings. The last update was made in 2004, when the NBIS was updated to define the qualifications and training requirements for inspection Team Leaders and Program Managers.

References: Happy 50th Anniversary National Bridge Inspection Standards - https://www.fhwa.dot.gov/highwayhistory/national_bridge_inspection_standards.cfm

How the NBIS relates to this site

The Recording and Coding Guide for the Structure Inventory and Appraisal of the Nation's Bridges (commonly referred to as the Guide), provides guidance in evaluating and coding specific bridge data during the bridge inspections. It defines each item, and the possible values that item can have. These coded items are considered to be an integral part of the nations bridge management system. Certain values from the NBI have been published on this website, and those values have been decoded for the ease of the users. The date that is provided on bridge sheets is described below:

Location

  • Bridge State and County

  • Feature Carried and Feature Crossed

  • Latitude and Longitude

    • The point of the coordinate is the beginning of the bridge in the direction of traffic.

  • Toll Status

    • Toll bridge. Tolls are paid specifically to use the structure.

    • On toll road. The structure carries a toll road, that is, tolls are paid to use the facility, which includes both the highway and the structure.

    • On free road. The structure is toll-free and carries a toll-free highway.

    • On Interstate toll segment under Secretarial Agreement. Structure functions as a part of the toll segment.

    • Toll bridge is a segment under Secretarial Agreement. Structure is separate agreement from highway segment.

  • Maintenance Responsibility

    • The primary agency responsible for the maintenance of the structure

  • Structure Open, Posted, or Closed to Traffic

    • Open, no restriction

    • Open, posting recommended but not legally implemented (all signs not in place or not correctly implemented)

    • Open, would be posted or closed except for temporary shoring, etc. to allow for unrestricted traffic

    • Open, temporary structure in place to carry legal loads while original structure is closed and awaiting replacement or

      rehabilitation

    • New structure not yet open to traffic

    • Bridge closed to all traffic

    • Posted for load (may include other restrictions such as temporary bridges which are load posted)

    • Posted for other load-capacity restriction (speed, number of vehicles on bridge, etc.)

History

  • Year Built

    • The year in which construction of the structure was completed.

  • Historical Significance

    • The historical significance of a bridge involves a variety of characteristics: the bridge may be a particularly unique example of the history of engineering; the crossing itself might be significant; the bridge might be associated with a historical property or area; or historical significance could be derived from the fact the bridge was associated with significant events or circumstances. The following options are used:

    • Bridge is on the National Register of Historic Places.

    • Bridge is eligible for the National Register of Historic Places.

    • Bridge is possibly eligible for the National Register of Historic Places (requires further investigation before determination can be made) or bridge is on a State or local historic register.

    • Historical significance is not determinable at this time.

    • Bridge is not eligible for the National Register of Historic Places.

    • The National Register of Historic Places can be found on the National Parks Service website: https://www.nps.gov/subjects/nationalregister/database-research.htm

  • Year Reconstructed

    • The year of the most recent reconstruction of the bridge.

    • For a bridge to be defined as reconstructed, the type of work performed must have been eligible for funding under any of the Federal-aid funding categories. The eligibility criteria would apply to the work performed regardless of whether all State or local funds or Federal-aid funds were used.

    • Some types of eligible work not to be considered as reconstruction are listed below:

      • Safety feature replacement or upgrading (for example, bridge rail, approach guardrail or impact attenuators).

      • Painting of structural steel.

      • Overlay of bridge deck as part of a larger highway surfacing project (for example, overlay carried across bridge deck for surface uniformity without additional bridge work).

      • Utility work.

      • Emergency repair to restore structural integrity to the previous status following an accident.

      • Retrofitting to correct a deficiency which does not substantially alter physical geometry or increase the load carrying capacity.

      • Work performed to keep a bridge operational while plans for complete rehabilitation or replacement are under preparation (for example, adding a substructure element or extra girder).

  • Picture Date

    • The date that Bridges in the USA visited the site and photographed the bridge.

Geometry

  • Lanes on Structure and Lane under Structure

  • Skew

    • The angle between the centerline of a pier (or abutments for single span) and a line normal to the roadway centerline.

    • When the structure is on a curve or if the skew varies between substructure elements, then the average skew is recorded.

  • Number of Main Spans and Number of Approach Spans

  • Main Structure Type and Approach Structure Type

    • Slab

    • Stringer/Multi-beam or Girder

    • Girder and Floorbeam System

    • Tee Beam

    • Box Beam or Girders - Multiple

    • Box Beam or Girders - Single or Spread

    • Frame (except frame culverts)

    • Orthotropic

    • Truss - Deck

    • Truss - Thru

    • Arch - Deck

    • Arch - Thru

    • Suspension

    • Stayed Girder

    • Movable - Lift

    • Movable - Bascule

    • Movable - Swing

    • Tunnel

    • Culvert (includes frame culverts)

    • Mixed types (only used for Approaches)

    • Segmental Box Girder

    • Channel Beam

    • Other

  • Main Structure Material and Approach Structure Material

    • Concrete

    • Concrete continuous

    • Steel

    • Steel continuous

    • Prestressed concrete (includes prestressed concrete)

    • Prestressed concrete continuous (includes prestressed concrete)

    • Wood or Timber

    • Masonry

    • Aluminum, Wrought Iron, or Cast Iron

    • Other

Condition

Condition ratings are used to describe the existing, in-place bridge as compared to the as-built condition. The condition describes the overall characterization of the general condition of the entire component being rated, not localized or nominally occurring instances of deterioration or disrepair.

  • Inspection Date

  • Deck Condition, Superstructure Condition, and Substructure Condition

    • Decks:

      • Concrete decks are inspected for cracking, scaling, spalling, leaching, chloride contamination, potholing, delamination, and full or partial depth failures.

      • Steel grid decks are inspected for broken welds, broken grids, section loss, and growth of filled grids from corrosion.

      • Timber decks are inspected for splitting, crushing, fastener failure, and deterioration from rot.

    • Superstructure:

      • The structural members are inspected for signs of distress which may include cracking, deterioration, section loss, and malfunction and misalignment of bearings.

    • Substructure:

      • All substructure elements are inspected for visible signs of distress including evidence of cracking, section loss, settlement, misalignment, scour, collision damage, and corrosion.

    • Ratings (used for all three elements):

      • Not Applicable

      • Excellent

      • Very Good - no problems noted.

      • Good - some minor problems.

      • Satisfactory - structural elements show some minor deterioration.

      • Fair - all primary structural elements are sound but may have minor section loss, cracking, spalling or scour.

      • Poor - advanced section loss, deterioration, spalling or scour.

      • Serious - loss of section, deterioration, spalling or scour have seriously affected primary structural components. Local failures are possible. Fatigue cracks in steel or shear cracks in concrete may be present.

      • Critical - advanced deterioration of primary structural elements. Fatigue cracks in steel or shear cracks in concrete may be present or scour may have removed substructure support. Unless closely monitored it may be necessary to close the bridge until corrective action is taken.

      • “Imminent” Failure - major deterioration or section loss present in critical structural components or obvious vertical or horizontal movement affecting structure stability. Bridge is closed to traffic but corrective action may put back in light service.

      • Failed - out of service - beyond corrective action.

  • Channel Condition

    • The physical conditions associated with the flow of water through the bridge such as stream stability and the condition of the channel, riprap, slope protection, or stream control devices including spur dikes.

    • Ratings (used for all three elements):

      • Not Applicable - Use when bridge is not over a waterway (channel).

      • Excellent - There are no noticeable or noteworthy deficiencies which affect the condition of the channel.

      • Very Good - Banks are protected or well vegetated. River control devices such as spur dikes and embankment protection are not required or are in a stable condition.

      • Good - Bank protection is in need of minor repairs. River control devices and embankment protection have a little minor damage. Banks and/or channel have minor amounts of drift.

      • Satisfactory - Bank is beginning to slump. River control devices and embankment protection have widespread minor damage. There is minor stream bed movement evident. Debris is restricting the channel slightly.

      • Fair - Bank protection is being eroded. River control devices and/or embankment have major damage. Trees and brush restrict the channel.

      • Poor - Bank and embankment protection is severely undermined. River control devices have severe damage. Large deposits of debris are in the channel.

      • Serious - Bank protection has failed. River control devices have been destroyed. Stream bed aggradation, degradation or lateral movement has changed the channel to now threaten the bridge and/or approach roadway.

      • Critical - The channel has changed to the extent the bridge is near a state of collapse.

      • “Imminent” Failure - Bridge closed because of channel failure. Corrective action may put back in light service.

      • Failed - Bridge closed because of channel failure. Replacement necessary.

  • Culvert Condition

    • The alignment, settlement, joints, structural condition, scour, and other items associated with culverts.

    • Ratings (used for all three elements):

      • Not Applicable - Not applicable. Use if structure is not a culvert.

      • Excellent - No deficiencies.

      • Very Good - No noticeable or noteworthy deficiencies which affect the condition of the culvert. Insignificant scrape marks caused by drift.

      • Good - Shrinkage cracks, light scaling, and insignificant spalling which does not expose reinforcing steel. Insignificant damage caused by drift with no misalignment and not requiring corrective action. Some minor scouring has occurred near curtain walls, wingwalls, or pipes. Metal culverts have a smooth symmetrical curvature with superficial corrosion and no pitting.

      • Satisfactory - Deterioration or initial disintegration, minor chloride contamination, cracking with some leaching, or spalls on concrete or masonry walls and slabs. Local minor scouring at curtain walls, wingwalls, or pipes. Metal culverts have a smooth curvature, non-symmetrical shape, significant corrosion or moderate pitting.

      • Fair - Moderate to major deterioration or disintegration, extensive cracking and leaching, or spalls on concrete or masonry walls and slabs. Minor settlement or misalignment. Noticeable scouring or erosion at curtain walls, wingwalls, or pipes. Metal culverts have significant distortion and deflection in one section, significant corrosion or deep pitting.

      • Poor - Large spalls, heavy scaling, wide cracks, considerable efflorescence, or opened construction joint permitting loss of backfill. Considerable settlement or misalignment. Considerable scouring or erosion at curtain walls, wingwalls or pipes. Metal culverts have significant distortion and deflection throughout, extensive corrosion or deep pitting.

      • Serious - Any condition described in Code 4 but which is excessive in scope. Severe movement or differential settlement of the segments, or loss of fill. Holes may exist in walls or slabs. Integral wingwalls nearly severed from culvert. Severe scour or erosion at curtain walls, wingwalls or pipes. Metal culverts have extreme distortion and deflection in one section, extensive corrosion, or deep pitting with scattered perforations.

      • Critical - Integral wingwalls collapsed, severe settlement of roadway due to loss of fill. Section of culvert may have failed and can no longer support embankment. Complete undermining at curtain walls and pipes. Corrective action required to maintain traffic. Metal culverts have extreme distortion and deflection throughout with extensive perforations due to corrosion.

      • “Imminent” Failure - Bridge closed. Corrective action may put back in light service.

      • Failed - Bridge closed. Replacement necessary.

  • Operating Rating

    • The operating rating is the absolute maximum permissible load which the structure may be subjected to.

    • If the bridge will not carry a minimum of 2.7 metric tons of live load, it shall be closed.

  • Inventory Rating

    • The inventory rating is the load which can safely utilize an existing structure for an indefinite period of time.

  • NBI Year

    • The publication year of the NBI data included for this bridge. Bridges will be kept up to date when possible, but all bridges may not be updated every year. For lost and closed bridges, this will be the last year that NBI data was published.

More Information

National Bridge Inventory (NBI) – Based on the Coding Guide: https://www.fhwa.dot.gov/bridge/mtguide.cfm

NBI Files: https://www.fhwa.dot.gov/bridge/nbi/ascii.cfm