state departments of transportation (DOTs) discre- tion to use funds not only for bridge rehabilitation and replacement, but also for a broad array of pre- ventive maintenance activities. Having a “worst- first” approach to bridge management by focusing only on replacing poor bridges while ignoring the maintenance needs of good and fair condition bridges is inefficient and cost-prohibitive in the long term. Bridge owners have taken advantage of the flexibilities in the HBP and have maintained their inventory in good to fair condition under con- strained resources. The Moving Ahead for Progress in the 21st Century Act (MAP-21) and the Fixing America’s Surface Transportation (FAST) Act recog- nized preservation as a vital component of achiev- ing and sustaining a desired state of good repair of highway facilities. The purpose of data from bridge inspec- tion programs required by the NBIS is safety, but this purpose has also adapted over the years to include bridge management (NBIS 2022). NBIS are mandated by federal statute at 23 U.S.C. 144 and implemented under 23 CFR 650 subpart C. This requires augmenting visual inspection with advanced technologies such as nondestructive evaluation (NDE) methods, corrosion analysis, and engineering structural health concepts to imple- ment objective decision-making processes for asset management (FHWA 2017). National Bridge Inspection Standards (NBIS) The inception of systematic bridge inspections in the United States can be attributed to the collapse of the Ohio River Bridge (known as the “Silver Bridge”) between Point Pleasant, West Virginia, and Gallipolis, Ohio, which killed 46 people. This failure led to the establishment of the NBIS that include inspection frequencies and qualifications (23 CFR 650.309, 650.311). Given the primary focus of NBIS establishment is safety (i.e., avoiding bridge failures) of bridge structures longer than 6 m (20 ft), NBIS were modified several times, mostly after notable bridge failures. For example, the failure of the Mianus River Bridge led to fracture-critical inspections, and the Schoharie Creek Bridge failure led to underwater bridge inspections with established intervals. Alampalli and Jalinoos (2009) and Ettouney and Alampalli (2011a, 2011b) discussed evolution of NBIS until 2004 which became effective in January 2005. They described the major provisions of NBIS in effect at that time, including inspection types and personnel qualifications, and then elaborated on the use of inspection data and NDE/NDT technol- ogies. This section describes changes to NBIS since then. AASHTO’s Manual of Bridge Evaluation (MBE) serves as a standard and provides uniformity in the procedures and policies for determining the physical condition, maintenance needs, and load capacity of the nation’s highway bridges. Changes made to NBIS in 2009 incorporated the MBE, 1st Edition, 2008 by reference, as FHWA felt that MBE aids bridge owners at all phases of bridge inspec- tion and evaluation (NBIS 2009). MAP-21 included a requirement for each state and appropriate federal agency to report element-level bridge inspection data to the Secretary, as each bridge is inspected, for all highway bridges on the National Highway System (NHS) (Title 23 U.S.C 144(d)(2).). To meet this requirement, FHWA asked state agencies to collect element-level data during all inspections of NHS bridges performed after 1 October 2014 (FHWA 2013). FHWA also issued the “Specification for the National Bridge Inventory Bridge Elements” (FHWA 2014) to provide the framework for bridge owners to collect and report element-level data to the FHWA. These data have to be collected in addition to other inventory data owners have already been collecting as per the Recording and Coding Guide for the Structure Inventory and Appraisal of the Nation’s Bridges (Coding Guide). All states now collect these data, which provides consistency and uniformity across the country. This is also meant to allow better data-driven performance-based deci- sions for bridge management. Some states like New York have shifted to element-level inspection of all bridges (both NHS and non-NHS) to maintain uni- formity across the state. The latest revision to NBIS as part of the rule-making process was published on 6 May 2022 (NBIS 2022), and key revisions are noted here. This regulation requires inspection of bridges on all public roads, on and off federal-aid highways, including tribally and federally owned bridges, and private bridges connected on each end by a public road (23 CFR 650.303). This revision rede- fined fracture critical member to nonredundant steel tension member, NSTM (23 CFR 650.305). It also requires the bridge inspection organizations to maintain a registry of nationally certified bridge inspectors (23 CFR 650.307). Even though there are several changes, the major shift in the regulations is toward the risk-based inspection interval. NBIS addresses the inspection frequency in two ways: (a) permissible inspection intervals for bridges based on the bridge component conditions to allow for extended routine inspection intervals up to 48 months, and 72 months for underwater inspections (23 CFR 650.311) and (b) more rigorous methods FEATURE | BRIDGEINSPECTION 26 M AT E R I A L S E V A L U AT I O N • J A N U A R Y 2 0 2 3 2301 ME Jan New.indd 26 12/20/22 8:15 AM

based on the consideration of condition and other factors that will allow for routine, underwater, and nonredundant steel tension member inspections that would allow some inspection intervals to be up to 72 months (23 CFR 650.311). The regula- tion requires written reports to FHWA of critical findings identified during inspections and provides minimum criteria for what a critical finding is, to maintain national consistency (23 CFR 650.313). The rule also introduced “Specifications for the National Bridge Inventory, SNBI” (23 CFR 650.317) (FHWA 2022a) to replace the ‘‘Recording and Coding Guide for the Structure Inventory and Appraisal of the Nation’s Bridges (Coding Guide)” introduced in 1995 (FHWA 1992). This is a major change including an expansion of component-level ratings to include bridge railings and their transi- tions, bearings, joints, channel, channel protection, and scour besides deck, superstructure, substruc- ture, culvert, and channel. A larger set of data is collected not only ensuring highway bridge safety but other considerations, including oversight of the National Bridge Inspection Program reporting to Congress emergency response administering a risk-based, data-driven, performance management program the National Performance Management Measures for Assessing Bridge Condition regulation (National 2017) and providing quality data through clarity and ease of use (FHWA 2022a). Full implementation of these changes is expected by Calendar Year 2028 (FHWA 2022b) due to time required to modify relevant software used by bridge owners, development of federal metrics and data-collection mechanisms, development of reg- ulation and policy changes in owner agencies, and so on. These changes to NBIS will not only continue the focus on improving safety but will move toward quality data collection for making better bridge management decisions, and thus supporting the asset management requirements. Role of Advanced Technologies in Bridge Inspection As noted earlier, the public expects not only safe bridges, but also reliability and uninterrupted mobility. This may be accomplished by supple- menting visual inspections with advanced NDE and structural monitoring technologies as well as uncrewed aerial systems (UAS) or robotic tech- niques so that bridge inspection does not require bridge closures that affect the mobility of the trav- eling public. These methods, combined with risk- based inspection intervals, will likely become preva- lent soon, especially with the implementation of the new NBIS. These advanced technologies have a big role to play in the coming years. Augmenting bridge inspections through these methods has the poten- tial to improve durability and minimize life cycle costs. The most practical of these systems are being used by owners during “in-depth” or “special” inspections or implemented for long-term monitor- ing. Some examples of advanced systems that are discussed in this special issue include the following: Ñ Inspection during and before opening to traffic is very important in ensuring durability and maintaining expected service life. The use of light detection and ranging (LiDAR), augmented reality, and technology fusion for data visualiza- tion of inspection data plays a major role. Sanei et al. (2023) summarize available technologies for quality control of reinforced concrete struc- tures during construction and focuses on using Red Blue Green Depth (RGBD) cameras for this purpose (see Figure 2). Ñ In recent years, the use of UAS has been intro- duced to improve data consistency, work effi- ciency, inspector safety, and cost-effectiveness during routine inspections. Advanced multi- sensor robotic platforms, such as ground-based systems (UGS) and uncrewed water-based systems (UWS), are also being used increasingly Figure 2. Use of RGBD camera for construction inspection. J A N U A R Y 2 0 2 3 • M AT E R I A L S E V A L U AT I O N 27 2301 ME Jan New.indd 27 12/20/22 8:15 AM COURTESY: DR. MOREU, UNIVERSITY OF NEW MEXICO