Updated: Aug 10, 2022
The Federal Highway Administration (FHWA) has recently announced an update to bridge inspection standards. Before moving on, though, let us briefly rewind the standards’ history.
Forty-six people lost their lives in the 1967 Silver Bridge collapse, bringing national attention to the issue of bridge condition safety. Soon after, the FHWA officially adopted the National Bridge Inspection Standards (NBIS) in 1971.
The NBIS updates, recognizing program administrative experience and technological advancements, were published in the Federal Register on May 6, 2022.
Effective June 6, 2022, this new regulation was mandated by the Moving Ahead for Progress in the 21st Century (MAP-21) Act, 2012.
The updated National Bridge Inspection Standards supersede the 2004 version. These standards apply to highway bridges on all public roads, including federally and tribally owned bridges. They also concern private bridges, the ends of which are connected to a public road.
This blog post describes some of the changes the new NBIS has brought about in the sphere of bridge inspections. Let’s take a deep dive.
Renaming fracture critical bridges as NSTM bridges
Many people incorrectly assume that fracture critical (FC) bridges are too dangerous to be used at all.
To do away with this mistaken assumption, the FHWA decided to replace the FC terminology with the term “nonredundant steel tension member” (NSTM), or simply, “nonredundant member”.
The update to bridge inspection standards defines an NSTM as a primary steel member without system, internal, or load path redundancy, and fully or partially in tension, the failure of which may cause the collapse of the entire bridge, or a portion of it.
Inspection interval requirements
How often do bridges need to be inspected?
As a rule of thumb, bridges should be inspected every 24 months. For intervals beyond 24 months, state DOTs can seek approval from the FHWA. However, the interval between inspections can span a maximum of 48 months.
The new standard provides options for bridge inspection organizations allowing a maximum of 72-month intervals for underwater bridge inspections, and extended routine inspection intervals of up to 48 months.
Going forward, federal agencies, state DOTs, and tribal governments need to follow a risk-based inspection interval method for their bridges.
FHWA’s new regulations prescribe two primary options for setting the intervals for routine, underwater, and NSTM bridge inspections:
Using a “simplified assessment of risk”, Method 1 requires state DOTs to classify each bridge into one of three risk levels corresponding to inspection intervals of 12, 24, or 48 months, respectively.
If a bridge inspector assigns a condition rating of ‘3’ or less to any bridge component (deck, superstructure, or substructure), it would mean that the bridge is in a serious or worse condition. In that case, the structure would have to be inspected at a minimum interval of 12 months.
However, if a bridge’s components are rated ‘6’ or greater (implying satisfactory or better condition), the inspection intervals can be up to 48 months. This leaves bridges with component condition ratings of ‘4’ and ‘5’ to have permissible inspection intervals of 24 months.
According to the Specifications for the National Bridge Inventory (SNBI), this method uses “a more rigorous assessment of risk”. Inspectors can use this method to categorize an individual bridge, or a group of bridges, into one of four risk levels corresponding to inspection intervals of 12, 24, 48, or 72 months.
Under this method, underwater bridges with components in serious or worse condition, rated ‘3’ or less, must be inspected every 24 months, at the most.
To determine extended or reduced inspection intervals under this method, agencies need to assess the risk by qualitative expert judgment or by quantified statistical analysis, when possible.
In fact, method 2 requires state DOTs to set up a risk assessment panel (RAP). This panel would consist of at least four well-experienced persons who will rigorously ascertain the level of risk for determining inspection intervals.
Out of those four members, at least two should be professional engineers (PEs). The panel’s interval criteria and policy must then be submitted to the FHWA for approval.
Also, bridge inspection organizations must tolerate an inspection interval of not more than three months beyond the inspection date. For intervals of less than 24 months, though, the tolerance time limit would be two months beyond the inspection date.
Technological advancements using drones
Inspections using Unmanned Aerial Systems (UAS) or drones have become widespread in recent years. In the new NBIS, the FHWA states that the use of UAS in inspections may depend on practical considerations, including lighting and the need to clean the bridge portion inspected.
Qualified personnel may use UAS in their national bridge inspection program to supplement some portions of an inspection. However, this will not apply to all aspects of an inspection, such as auditory cues or live load response.
Drone operators must also comply with other regulatory and statutory requirements, including those governing public aircraft. A team leader for a UAS inspection, for instance, should be on-site throughout the duration of the inspection.
Other regulations in the update to bridge inspection standards
One of the most-awaited updates to the bridge inspection standard is the new document meant to identify data items for the National Bridge Inventory (NBI). Called the "SNBI", this document replaces the FHWA “Recording and Coding Guide for the Structure Inventory and Appraisal of the Nation’s Bridges (Coding Guide)”, 1972. From now on, federal agencies, state DOTs, and tribal governments must report NBI data to the FHWA using the instructions and data items in the SNBI.
The Specification for the National Bridge Inventory – Bridge Elements (SNBIBE), 2014, has been merged with the SNBI.
The new bridge inspection standards define a critical finding as “any condition posing an imminent threat to public safety that demands an immediate response”. These standards also state that to be identified as a critical finding, the superstructure, substructure, scour, or channel condition rating must be critical (‘2’) or worse. At the same time, the NBIS updates call for reporting critical findings to the local FHWA Division Office through an email or over the phone. Such reports are to continue monthly, or as requested, until each critical finding is resolved.
Bridge inspection organizations must provide information to the FHWA for annual compliance reviews. The updated NBIS also covers new timeframes for updating bridge inventory data, along with a process for tracking those inventory data updates.
All bridges with routine inspection intervals greater than 48 months need service inspections. Personnel with general knowledge of bridge inspection or maintenance can perform service inspections to identify critical safety issues. These service inspections would be much cheaper and less rigorous than routine inspections.
In addition, the updated regulations specify compulsory qualifications for bridge inspection team leaders and inventory managers. Their other provisions also include requirements for training bridge inspectors.
Plus, agencies and state DOTs need to maintain a registry of nationally certified bridge inspectors. This provision was included in the National Bridge Inspection Standards to align with a similar requirement laid down in the National Tunnel Inspection Standards (NTIS), 2015.
The new NBIS repeals two outdated regulations: the “Discretionary Bridge Candidate Rating Factor” and the “Highway Bridge Replacement and Rehabilitation Program” (HBRRP).
The “Parallel Structure Designation” item (Item no. 101) from the previous coding guide has been discontinued.
More reliable inspections
According to the new NBIS regulations, the interval for inspecting safer bridges can be rationally extended to every 48 or 72 months.
So, instead of over-inspecting newer and healthier bridges, bridge owners can focus more on structures that actually require more attention.
Further benefits brought about by the changes in the NBIS may include:
Ability to identify deteriorating conditions on bridges sooner than under the existing rule, due to increased inspections (at 12-month intervals rather than the current 24-month interval) for safety-critical bridges
Faster implementation of safety mitigation measures, including repairs, bridge closures, or a reduction in permitted load weights
Less risk of negative safety effects from sudden deterioration of bridges at lower condition ratings
Better allocation of limited inspection program resources
More consistent reporting on safety-related or structural deficiencies
Better qualifications for bridge inspection personnel
Preparing for the future
Along with the update to the bridge inspection standards, the transition from the previous coding guide to the SNBI would require significant efforts on the part of bridge inspection organizations.
The FHWA has provided a Data Crosswalk for "Over" and "Under" bridge records to define the relationship between the SNBI and the previous coding guide. From 2023, they intend to offer free training on the usage and understanding of the SNBI.
They also expect to develop a computer-based tool by 2023 to accurately transition bridge data from the previous format to the SNBI format.
Thankfully, you don’t have to wait for such a long time to start the transition process to the SNBI format. With inspectX, you can begin the process of moving to the updated National Bridge Inspection Standards straightaway.
Allowing tablet-based inspections, inspectX lets you collect field data offline as per the SNBI coding guide. You can even take photos and draw sketches on the tablet, associating those with their respective data items and defects.
So, book a call with us or watch a demo of inspectX now.