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Bridges & Structures

Subject: INFORMATION: Public Disclosure of National Bridge Inventory (NBI) Data Date: May 17, 2007
From: /s/ Original Signed by
M. Myint Lwin, P.E., S.E. Director,
Office of Bridge Technology
Refer To: HIBT-30
To: Associate Administrators
Chief Council
Directors of Field Services
Federal Lands Highway Division Engineers
Resource Center Director
Division Administrators


The purpose of this memorandum is to update and clarify the policy of the Federal Highway Administration (FHWA) regarding public disclosure of National Bridge Inventory (NBI) data. The updated policy is intended to replace all prior policies, both formal and informal.

National Bridge Inventory (NBI)

The NBI is a collection of information (database) covering just under 600,000 of the Nation's bridges located on public roads, including Interstate Highways, U.S. highways, State and county roads, as well as publicly-accessible bridges on Federal lands. It presents a State by State summary analysis of the number, location, and general condition of highway bridges within each State.

Collection of NBI data is authorized by statute, 23 U.S.C. 151 (National Bridge Inspection Program), and implemented by regulation, 23 CFR 650.301 et seq. In accord with these authorities, the FHWA established National Bridge Inspection Standards (NBIS) for the safety inspection and evaluation of highway bridges; and each State is required to conduct periodic inspections of all bridges subject to the NBIS, prepare and maintain a current inventory of these structures, and report the data to the FHWA using the procedures and format outlined in the Recording and Coding Guide for the Structure Inventory and Appraisal of the Nation's Bridges.

After evaluation of the inspection data, the FHWA provides States with a list of bridges that are eligible for replacement or rehabilitation. The FHWA uses the data to submit a required biannual report to Congress on the status of the Nation's bridges, to publish an Annual Materials Report on New Bridge Construction and Bridge Rehabilitation in the Federal Register, and to apportion funds for the Highway Bridge Program.

Use of the NBI data also enables FHWA to satisfy its requirements under 23 U.S.C. 144, which mandate the inventory, classification, cost estimates for replacement or rehabilitation, and assignment of replacement or rehabilitation priorities for all highway bridges on all public roads.

Current Policy on Public Disclosure of NBI Data

The FHWA receives requests for NBI data from a number of different sources, including: private citizens, public interest groups, consultants, the press, academics, government agencies, and others. Currently, in response to requests from non-governmental sources, whether informal or submitted under the Freedom of Information Act (FOIA), FHWA provides a CD containing ASCII flat files extracted from the database, with the exception of four data elements: latitude, longitude, critical facility indicator, and STRAHNET indicator. In response to requests from governmental sources, FHWA provides all data elements and, in addition, generates specific queries and lists, as necessary.

Prior Policies on Public Disclosure of NBI Data

No policy regarding disclosure appears to have been in effect from 1972, when the electronic database was assembled, to 1978. Given the newness of the program and the cumbersome and lengthy process of generating downloads from a mainframe computer to tape, few disclosures were probably sought.

However, by memorandum dated February 27, 1978, the then Associate Administrator for Engineering and Traffic Operations designated eight NBI data elements "For Official Use Only," thereby ending disclosure of that information to all but governmental entities. Some of the withheld elements were those currently withheld, but others were different, or are no longer included in the current database.

Subsequently, by memorandum dated December 8, 1997, the 1978 memorandum was rescinded, and all NBI data elements were made available for disclosure. The memorandum noted that the need to restrict release of the data had changed since 1978, particularly in view of the availability of modern technologies that could accurately locate objects on earth and the fact that the Military Traffic Management Command (MTMC), now the Surface Deployment Distribution Command (SDDC), no longer supported withholding NBI information. Following this policy change, FHWA placed the NBI data on its Web site, enabling any person to access and download it.

After the events of September 11, 2001, FHWA removed the NBI data from its Website and instituted the current policy of withholding from general public disclosure the four elements identified above. No memorandum or announcement of the new policy was issued.


As this information makes clear, the FHWA's policies regarding public disclosure of NBI data have developed and changed over time, often in response to changing civic realities and developments in technology. The FHWA has determined that re-examination and clarification of its NBI disclosure policy at the present time would be appropriate, understanding that future events and technological developments may necessitate future revisions or modifications.

The NBI database is an information tool. It compiles existing information in a standard format. This tool supports the FHWA's bridge programs, including the Highway Bridge Program and the National Bridge Inspection Program. The data assists the FHWA in meeting Federal responsibilities and reporting requirements and assists the States in meeting national bridge inspection standards. Information entered in the database is collected and maintained with public funds.

More importantly, the NBI data does not present information not otherwise publicly available that would likely assist persons in targeting a specific structure or planning an attack on a structure. Therefore, withholding NBI data elements from public disclosure does not improve transportation security or provide additional protection for particular structures

Review of the four data elements currently withheld from disclosure support this conclusion. For example, latitude and longitude information is widely available; and advances in internet-based technologies, including surveillance and mapping tools, make access to NBI data unnecessary for locating a structure. Similarly, information comprising the data element called "critical facility indicator" is likely available elsewhere and has not been collected for the NBI since 1995. Finally, SDDC (then MTMC) indicated in 1997 that it did not object to disclosure of STRAHNET indicator information and recently reaffirmed this position, noting that STRAHNET is not a definitive routing guide for military deployments nor independently sensitive information. In fact, several States have put STRAHNET maps on their Web sites.

It is also noteworthy that a recent study found that because potential terrorists have numerous options for gathering mission-critical attack information, government Agency data is unlikely to be a primary source of information. The study found that less than 1 percent of 629 Federal data sets reviewed by researchers appeared to have notable value for would-be attackers. Mapping the Risks: Assessing the Homeland Security Implications of Publicly Available Geospatial Information, RAND Corp. (2002). The September 11 attacks, as well as subsequent events in Madrid and London, demonstrate a terrorist focus on easily identified and highly symbolic targets, which do not require government information for selecting or planning an attack. For such targets, specific intelligence, security planning, and on-site security are more important to transportation security than restricting access to most governmental databases.

Moreover, it is the policy of the U.S. Department of Transportation that the identification and protection of sensitive information, while important, must be balanced in every case against the public's legitimate interest in, and right to know, how the Department carries out its responsibilities. In this case, information concerning the condition of bridges located in every State that also forms the basis of decisions regarding the expenditure of public funds for their rehabilitation or replacement is a matter of legitimate public interest; and non-disclosure of NBI data does not improve transportation security or protect particular structures. For these reasons, the FHWA has concluded that its 2001 policy withholding certain NBI data elements from requesters can no longer be supported.


Effective immediately, in responding to public requests for NBI data, FHWA will make all data elements available for disclosure.

Updated: 10/05/2022
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