Contents

• Introduction
• Bridge Characteristics
• Bridge Inspection
• Bridge Conditions
• Bridge Vulnerabilities to Extreme Events
• Bridge Infrastructure Funding
• Federal and State Roles
• Congress and Bridge Policy
• Bridge Funding and the IIJA
• New Bridge Programs
• Bridge Formula Program
• Bridge Investment Program
• Federal Lands and Tribal Bridges
• Other Program Sources of Bridge Funding
• FHWA's Emergency Relief Program
• Non-bridge Programs That Can Assist Bridge Projects
• Annual Appropriated Funds
• Bridge Spending History, FY2016-FY2025
• Future Bridge Funding Needs
• Issues for Congress
• Bridge Funding Programs
• Type of Funding Distribution
• Nonfederal Funding for Bridges
• Spending on Off-System Bridges

Summary

The United States has approximately 624,000 bridges longer than 20 feet on public roads. About 48% of these bridges are owned by state governments and 50% by local governments. The number of bridges classified as poor has declined gradually for many years, but as of June 2025, about 42,000 remain. The Infrastructure Investment and Jobs Act (IIJA; P.L. 117-58), enacted on November 15, 2021, established federal programs specifically to fund bridges for the first time since FY2012 and significantly increased the total amount of federal funding that can be used for bridge construction and repair. The IIJA provided funding for FY2022 through FY2026.

The IIJA created two large stand-alone bridge programs, the Bridge Formula Program and the Bridge Investment Program, authorized at $27.5 billion and $15.8 billion, respectively, over five years. In addition, the average annual authorizations for the so-called core highway programs that can provide funding for both roads and bridges were increased by roughly 26% over the FY2021 baseline unadjusted for inflation; this money is distributed by formula to the states, which can use it for bridge projects at their discretion. The IIJA also increased funding of existing discretionary surface transportation programs and created several new discretionary programs to which local entities and the states can apply directly to the U.S. Department of Transportation. Bridge projects that match the program criteria are eligible under some of these programs.

Adjusted for inflation, average annual bridge spending (as measured by funding obligations) has been 22% higher in the IIJA period (FY2022-FY2025) to date than under the previous authorization law, the Fixing America's Surface Transportation Act (FAST Act; P.L. 114-94 ) as extended (FY2016 through FY2021). Average annual spending has been $12.0 billion in the IIJA period to date and $9.8 billion in the FAST Act period (FY2025 dollars). Based on an analysis by the Federal Highway Administration of bridge funding needs, this level of spending combined with nonfederal spending could reduce the bridge investment backlog by about 90% if continued over a 20-year period, although additional funds would be needed for the construction of new bridges.

The vast majority of bridges in poor condition, over four out of five, are in rural areas. These bridges tend to be small and relatively lightly traveled. In urban areas, bridges in poor condition, while far fewer, are generally much larger and, therefore, more expensive to fix. In 2025, 58% of the deck area classified as in poor condition was on urban bridges. Bridges on roads carrying heavy traffic loads, particularly Interstate Highway bridges, are generally in better condition than those on more lightly traveled routes. Although improvements have been made in most states, there remain major differences among states in the share of bridges in poor condition. For example, about 18% of bridges in West Virginia were classified as poor in 2025, whereas in Nevada the share was 1%. The IIJA reaffirmed congressional support for the improvement of bridges on smaller roads that are not part of the federal-aid system by making these so-called "off-system bridges" eligible under the new bridge programs.

The IIJA replaced the former policy of gradual improvement of the nation's bridges with a more ambitious program to speed up the pace of bridge improvements. The implementation of this policy and its success in improving bridge conditions are likely to be of ongoing concern to Congress. Other potential issues in reauthorization of the IIJA include

• the reduction in funding flexibility afforded state DOTs by dedicated bridge programs;
• the competitive distribution of some bridge funding—competitive funding has the potential of focusing funds on bridge projects with the greatest benefits, but state DOTs generally prefer formula funds that provide known funding amounts with less administrative effort;
• whether the large increase in federal grants for bridges under the IIJA has discouraged state and local funding, including the use of tolling as a funding option; and
• the eligibility of off-system bridges and whether the repair or replacement of more heavily traveled bridges on major roads would constrain resources.

Introduction

The United States has approximately 624,000 bridges longer than 20 feet on public roads. The number of bridges classified as poor has declined gradually for many years, but as of June 2025, about 42,000 remain. Most of these bridges are owned and maintained by state and local governments. The federal government has established bridge inspection standards and provides funding to support the rehabilitation and replacement of existing bridges and the construction of new bridges. Bridges in poor condition can be restricted by weight, and unsafe bridges are typically closed to traffic. Failures due to poor conditions have occurred, such as the Fern Hollow Bridge in Pittsburgh, PA, in 2022 that caused several injuries but no deaths.¹ Poor bridge conditions can cause severe disruption to the highway system.

The passage of the Infrastructure Investment and Jobs Act (IIJA; P.L. 117-58), covering the years FY2022-FY2026, initiated a major change in congressional bridge funding policy. Prior to passage, federal bridge funding came from programmatic sources that could be spent on either roads or bridges in accordance with priorities set by the states. The IIJA authorized $43.3 billion over five years exclusively for bridge projects; increased authorizations for formula grants that states may choose to use for bridges; and expanded funding for discretionary programs under which bridge projects are eligible.

This report examines current bridge characteristics and conditions, national funding needs, and the implications of the attempt in the IIJA to speed up the pace of bridge improvements. It concludes with a discussion of issues that may be of congressional concern, especially in reauthorization of the surface transportation programs, including the potential impact of inflation on future bridge spending, the future of toll-funded bridges, and spending on bridges not on the federal-aid system.

Bridge Characteristics

Of the 624,000 bridges on public roads, about 48% are owned by state governments, and 50% are owned by local governments. State governments generally own the larger and more heavily traveled bridges, such as those on the Interstate Highway system. Less than 2% of highway bridges are owned by the federal government, primarily those on federally owned land.²

About 9% of all bridges carry Interstate Highways, and another 15% serve principal arterial highways other than Interstates.³ Interstate and other principal arterial bridges carry about 80% of average daily bridge traffic. The highest traffic loads are on Interstate Highway bridges in urban areas; these accounted for only 6% of all bridges but carried 37% of average daily bridge traffic in 2025.⁴

Bridge Inspection

Under the National Bridge Inspection Program, all bridges longer than 20 feet on public roads must be inspected by qualified inspectors, based on federally defined requirements (23 U.S.C. §144). Federal agencies are subject to the same requirements for federally owned bridges, such as those on federal lands. Data from these inspections are reported to the Federal Highway Administration (FHWA), which uses them to compile a list of bridges in poor condition. States may use this information to identify which bridges need replacement or repair.⁵

FHWA oversees bridge inspection through the National Bridge Inspection Standards (NBIS).⁶ The NBIS set forth how, with what frequency, and by whom bridge inspection is to be completed. The standards provide the following:

• Each state is responsible for the inspection of all public highway bridges within the state except for those owned by the federal government or Indian tribes. Although the state may delegate some bridge inspection responsibilities to smaller units of government, the responsibility for having the inspections done in conformance with federal requirements remains with the state.
• Inspections can be done by anyone qualified under the standards for qualification and training. The inspectors may be state employees, consultants to the states, or others.
• Inspection of a federally owned bridge is the responsibility of the federal agency that owns the bridge.
• In general, a bridge must be inspected at least every 24 months. States are to identify bridges that require less than a 24-month interval. States can also request FHWA approval to inspect certain bridges at intervals as long as 48 months. The interval for an underwater inspection is generally 60 months but may be increased to 72 months with FHWA permission. Nonredundant steel tension members must undergo a hands-on inspection at intervals not to exceed 48 months.⁷
• An on-site inspection team must have a leader who meets additional training requirements. Damage and special inspections do not require the presence of a team leader.
• Load rating of a bridge must be under the responsibility of a registered professional engineer. Structures that cannot carry maximum legal loads for the roadway must be posted.

The vast majority of inspections are performed under state authority. FHWA bridge engineers, at times, perform field reviews to assure that states are complying with the bridge inspection requirements. FHWA also provides on-site engineering expertise in the examination of the causes of catastrophic bridge failures.

Bridge Conditions

Bridge condition data reported to FHWA are collected in the National Bridge Inventory. This information permits FHWA to characterize the existing condition of bridges as good, fair, or poor. A bridge is considered in good condition if the deck, superstructure, and substructure are rated at least 7 on a 0-9 scale. If any of these bridge elements is rated 5 or 6, a bridge is considered in fair condition. A bridge is considered in poor condition if any element is rated 4 or less. A bridge classified as poor is not necessarily unsafe but may require the posting of a vehicle weight restriction. When officials determine that a bridge is unsafe, it is closed to traffic. In 2025, about 3,600 (less than 1%) bridges were closed and another 62,000 (10%) had a weight restriction.⁸

In 2025, 272,000 public road bridges (44%) were considered good, 310,000 (50%) fair, and 42,000 (7%) poor. The number of poor bridges declined by about 15,000 over the 14-year period from 2012 to 2025, whereas the number of bridges in good condition dropped by 14,000, and the number of bridges in fair condition increased by 47,000 (Table 1).

About 80% of the bridges in poor condition in 2025 were located in rural areas. Nevertheless, urban bridges in poor condition are generally much larger and carry more traffic than those in rural areas and, therefore, are more expensive to fix. In 2025, 58% of the total deck area of bridges in poor condition was in urban areas. The amount of deck area in poor condition has dropped by about the same proportion in urban and rural areas from 2012 through 2025, roughly 30% (Figure 1).

Bridges on Interstate Highways are generally in better condition than those on more lightly traveled routes: 3% of urban Interstate Highway bridges were considered poor in 2025, whereas 6% of urban bridges on local roads were classified as poor.⁹ Likewise, 3% of rural Interstate Highway bridges were poor in 2025, compared with 10% of rural bridges on local roads. In 2025, 9% of bridges owned by local governments were classified as poor, compared with 4% of state-owned bridges. For bridge condition ratings by state and territory, see Table A-1.

Figure 1. Urban and Rural Highway Bridges in Poor Condition, 2012-2025

Source: Bureau of Transportation Statistics, National Transportation Statistics, Table 1-28, https://www.bts.gov/content/condition-us-highway-bridges. Notes: Bridge counts and conditions for 2012-2020 were finalized and published as of December 31 of each year. Beginning in 2021, bridge counts and conditions were finalized and published as of June 15 of each year.

Bridge Vulnerabilities to Extreme Events

In addition to obsolescence and deterioration due to aging and vehicle use, bridges are vulnerable to other kinds of risks, sometimes called "extreme events," including natural hazards (earthquakes, flooding, wildfires, etc.), vehicle fires, and vessel strikes.¹⁰ Bridges can be made more resilient to these risks by initial design or by retrofitting. Some states in the western United States, for instance, have been following seismic design practices since the early 1970s, after the 1971 San Fernando, CA, earthquake.¹¹ In many situations, identifying risks can be difficult and the mitigation costs can be prohibitive.

Public awareness about the vulnerability of certain bridges to vessel strikes was heightened when, on March 26, 2024, the containership Dali collided with the Francis Scott Key Bridge in Baltimore, MD, causing it to collapse. As part of its investigation of the incident, the National Transportation Safety Board (NTSB) completed a vulnerability assessment of the Key Bridge to collapse from a vessel strike.¹² NTSB concluded that the Key Bridge was above an acceptable threshold of collapse risk from a vessel strike as established by the American Association of State Highway and Transportation Officials (AASHTO). NTSB "also identified 68 other bridges frequented by ocean-going vessels that were constructed before the AASHTO guidance was issued in 1991, have not undergone a vulnerability assessment based on recent vessel traffic, and, therefore, have an unknown level of risk of collapse from a vessel collision."¹³ Thus, NTSB called on these bridge owners to conduct an assessment and, if necessary, to "develop and implement a risk reduction plan that includes input from the interdisciplinary team [consisting of FHWA, Coast Guard, and Corps of Engineers], identifies short- and long-term strategies to reduce risk, and considers the safety of the vessels and structures in the waterways."¹⁴

According to NTSB, as of November 25, 2025, bridge owners of 22 of the 68 bridges had reported that they were under the AASHTO threshold, and 14 were over the threshold with risk reduction planning in progress. Vulnerability assessments of the remaining 32 bridges were reported as being "in progress."¹⁵ According to one news report, the Delaware River Port Authority is developing protection for two bridges at risk of vessel strikes—the Benjamin Franklin Bridge and the Walt Whitman Bridge. Costs of these projects were reported as being "about $100 million to $150 million for each bridge." Some vulnerable bridges, such as the Chesapeake Bay Bridge in Maryland, might need to be replaced, presumably at greater cost than adding protection to existing facilities.¹⁶

Bridge Infrastructure Funding

Federal and State Roles

Federal bridge funding shares the basic attributes of federal aid to highways, which is administered by FHWA.¹⁷ Most of this funding is apportioned by formula to the states from the Highway Trust Fund and is not subject to annual appropriation by Congress. Each state's funds are divided among 10 so-called core formula programs established by law. State departments of transportation (state DOTs) are free to spend the funds allocated to each program in any way consistent with that program's purposes, so long as they comply with detailed federal planning guidelines and performance management measures.¹⁸ State DOTs execute the contracts and oversee the construction process. The decision about how much of a state's formula funding to spend on bridges rather than roads is generally up to the state DOT.¹⁹ States are allowed to transfer ("flex") up to 50% of each core formula program's apportioned funds to other formula programs.²⁰ Most bridge projects receive a federal cost share of up to 80%, but for bridges on Interstate Highways, the share is generally up to 90%. The use of federal funds for bridges, unlike most road funding, is not restricted to designated federal-aid highways and may be used on any bridge listed in the National Bridge Inventory.

In addition, states or municipalities may seek discretionary (competitive) grants awarded by FHWA or the Office of the Secretary of Transportation. For example, the Nationally Significant Freight and Highway Projects Program (renamed INFRA) also may award funding for large bridge projects.²¹

Congress and Bridge Policy

For the first 53 years of federal aid to highways, federal policy left decisions about allocating money to bridge projects to the states. There was no federal program funding dedicated to bridges. This changed following the collapse of the so-called Silver Bridge over the Ohio River in December 1967, which resulted in the deaths of 46 people. Congress required the Secretary of Transportation to establish the NBIS in 1968. In February 1970, FHWA reported that of the 563,000 bridges in the United States, 88,900 were "critically deficient." Despite the findings, the agency recommended against funding a "special bridge program" on the grounds that such a program would "necessarily be at the expense of other urgent highway needs."²²

Contrary to this recommendation, the Federal-Aid Highway Act of 1970 (P.L. 95-599) authorized the discretionary Special Bridge Replacement Program, the first stand-alone federal highway bridge funding program. Having a stand-alone program was a way for Congress to dedicate certain funding to bridges rather than roads. The Surface Transportation Assistance Act of 1978 (P.L. 95-599) replaced this with a new formula-based Highway Bridge Replacement and Rehabilitation Program, which expanded eligibilities to include bridge rehabilitation and projects on off-system bridges. Roughly 20% of the program's funding was set aside for a bridge discretionary program for large bridge projects. These discretionary funds were under the control of FHWA.

The 1991 Intermodal Surface Transportation Efficiency Act (P.L. 102-240) allowed a state to transfer 40% of its bridge apportionment to other highway programs (the percentage was increased to 50% in 1998). The Moving Ahead for Progress in the 21^st Century Act (MAP-21; P.L. 112-141), enacted in 2012, allowed the dedicated bridge program—then called the Highway Bridge Program—to expire at the end of FY2012, largely returning the decision to the states on how much of their federal formula grants to spend on bridges. This situation persisted until Congress passed the IIJA, which reasserted bridge spending as a congressional priority.

Bridge Funding and the IIJA

The IIJA both reauthorized spending authority from the Highway Trust Fund for highway programs at an increased level and provided an additional boost to infrastructure spending via multiyear supplemental appropriations from the Treasury general fund. Some programs were authorized to receive additional funding subject to appropriation in future annual appropriations acts.

New Bridge Programs

The IIJA created two stand-alone programs dedicated to bridge projects:

• The Bridge Replacement, Rehabilitation, Preservation, Protection, and Construction Program, generally referred to as the Bridge Formula Program (BFP), was authorized at $5.50 billion annually through FY2026.
• The Bridge Investment Program (BIP) was authorized at an annual average $3.15 billion in competitive grants through FY2026, although an annual average $0.65 billion of that amount was subject to future appropriations (see Table 2).

Bridge Formula Program

BFP funds are distributed to states (including the District of Columbia and Puerto Rico) based on each state's cost to replace its poor-condition bridges and to rehabilitate its fair-condition bridges, relative to the total nationwide cost.²³ The IIJA funds the program with $5.5 billion annually over the life of the act. The minimum amount a state will receive is $45 million annually. At least 15% of each state's funds must be spent on bridges not on the federal-aid system, so-called "off-system bridges," and $165 million (3%) is set aside annually for bridges on tribal lands.²⁴ Off-system bridges, owned by sub-state government entities or federally recognized tribes, are eligible for a 100% federal share. State DOTs choose the projects, other than for tribal lands bridges. The funds may be used for highway bridge replacement, rehabilitation, preservation, protection, or construction projects on any bridge listed in the National Bridge Inventory or any new highway bridge that upon completion would be included in the inventory. BFP funds may not be transferred to other programs. This formula program is entirely funded with multiyear appropriations from the general fund.

Bridge Investment Program

The BIP provides competitive grants for bridge replacement, rehabilitation, preservation, or resiliency improvements for bridges on the National Bridge Inventory.²⁵ The IIJA authorizes an average annual $3.153 billion for the program, of which roughly one-fifth is subject to annual appropriations. A state or group of states, sub-state governmental entities or groups of such entities, special purpose districts or public authorities that serve a transportation function, metropolitan planning organizations that serve populations over 200,000, federal land management agencies, tribal governments, or any combination of the aforementioned entities may apply directly to the U.S. Department of Transportation. BIP grants can be used to replace, rehabilitate, preserve, or protect (including adding resilience features) bridges or to replace or rehabilitate culverts to improve flood control and habitat connectivity for aquatic species. A grantee may also use BIP funding to pay subsidy costs of a federal loan under the Transportation Infrastructure Finance and Innovation Act (TIFIA).

The program creates three categories of projects for which eligible entities may apply:

• $20 million is set aside annually for planning, feasibility analysis, and revenue forecasting grants. There is no minimum size for planning grants.
• Large Bridge Project grants are available for projects with total eligible costs of greater than $100 million. The maximum award may not exceed 50% of the total eligible project cost, making the minimum award amount $50 million. The award may be split into a multiyear award over four consecutive fiscal years.
• Bridge Project grants are available for projects with total eligible costs of $100 million or less. The maximum award may not exceed 80% of the total eligible project cost, and the minimum award is $2.5 million.

The IIJA allows up to 5% of BIP funding to be used for eligible projects that consist solely of culvert replacement or rehabilitation of bridge-sized culverts (as defined under 23 C.F.R. §650.305) for flood control or to improve habitat connectivity for aquatic species.

Other sources of federal assistance may be used to satisfy the nonfederal share as long as the total federal share does not exceed the amount allowable under 23 U.S.C. §120 or 23 U.S.C. §124 for off-system bridges. For a federal land management agency, tribal government, or a consortium of tribal governments, federal funds made available under non-BIP federal programs (including Tribal Transportation Program and Federal Lands Transportation Program funds) may be used to pay the remaining cost of a BIP project.

Federal Lands and Tribal Bridges

Most funding for highways and bridges owned by the federal government or by Indian tribes does not come from the regularly apportioned programs discussed above. Funding is authorized separately, primarily from two stand-alone programs: the Tribal Transportation Program and the Federal Lands Transportation Program.²⁶ The Tribal Transportation Program funds are under the control of the tribes, in cooperation with the Department of the Interior and the Department of Transportation. The Federal Lands Transportation Program funds are under the control of the federal land management agencies, with assistance and oversight from the Department of Transportation. A third program, the Federal Lands Access Program, funds facilities that provide access to federal lands. The use of these funds in each state is determined by a state committee that includes representatives of FHWA, the state DOT, and a political subdivision of the state.

Compared with the core highway formula programs, these programs are small. The IIJA provided $602 million annually for the Tribal Transportation Program and $439 million annually for the Federal Lands Transportation Program. The Federal Lands funding amount is divided among the National Park Service ($346 million), the Fish and Wildlife Service ($36 million), the U.S. Forest Service ($26 million), and other federal land management agencies ($31 million). The IIJA provided $298 million annually for the Federal Lands Access Program. These three programs' funds must cover road and bridge needs, and the funds may be used on public transportation projects. These programs are paid for from the Highway Trust Fund.

The IIJA also provided $205 million per year specifically for tribal bridges with funding set aside from the larger bridge programs, a sizable increase for tribal bridges annually under prior law, and $55 million annually under the National Significant Federal Lands and Tribal Projects Program. The IIJA created several new discretionary highway and bridge grant programs for which tribal projects are eligible.

Other Program Sources of Bridge Funding

Broad sources of highway funding for states to improve their bridges existed prior to the IIJA and have been continued at increased funding levels. In particular, three of these formula programs—the Surface Transportation Block Grant Program, the National Highway Performance Program, and the National Highway Freight Program—together have been the major sources of bridge funding since FY2013 and continue to be available for bridge projects. Funding from other legacy formula programs, such as Transportation Alternatives and the Congestion Mitigation and Air Quality Improvement Program, also can be used, depending on the specifics of the project.

FHWA's Emergency Relief Program

The Emergency Relief Program provides funding for bridges damaged in natural disasters or that are subject to catastrophic failures from an outside source.²⁷ The program provides funds for emergency repairs to restore essential travel immediately after the failure to restore essential traffic, as well as for longer-term permanent repairs.

The IIJA changed the time frame within which the federal government will pay 100% of the cost of emergency repairs from 180 days to 270 days from the date of the disaster. Later repairs, as well as permanent repairs, such as reconstruction or replacement of a collapsed bridge, are reimbursed at the same federal share that would normally apply to the federal-aid highway facility. The IIJA strengthens the language permitting the funding of added protective features to include features that are economically justifiable improvements that will mitigate the risk of recurring damage from extreme weather, flooding, and other natural disasters. The act also adds a list of eligible protective features under the program.

Francis Scott Key Bridge (Maryland)

In certain circumstances, Congress has provided funding or special conditions for specific emergency relief (ER) projects. The American Relief Act (P.L. 118-58), enacted in December 2024, provided 100% ER funding for response to damage caused by the cargo ship Dali to the Francis Scott Key Bridge in Maryland, less any amounts recovered through compensation, insurance, and other such payments.²⁸

Non-bridge Programs That Can Assist Bridge Projects

The IIJA created new formula and competitive grant programs that, while not stand-alone bridge programs, can provide funding for bridge projects, depending on the specifics of the project. Among these programs are the following:

• Promoting Resilient Operations for Transformative, Efficient, and Cost-saving Transportation (PROTECT) funds can be used for bridge-related infrastructure resilience spending. The IIJA funded this new core formula program at an annual average of $1.46 billion. The act also created a PROTECT competitive grant program funded at an annual average of $300 million.
• Rural Surface Transportation Grant Program was funded at an annual average of $400 million.
• Nationally Significant Projects Program (also referred to as MEGA) is a multimodal program designed to fund large, complex transportation infrastructure projects, including highway bridges. The program was funded at $1 billion annually from multiyear appropriations and authorized to receive an additional $2 billion annually, subject to appropriation. The program is administered by the Office of the Secretary of Transportation.
• National Culvert Removal, Replacement, and Restoration Grant Program is a multimodal program administered by the Office of the Secretary that funds projects that improve or restore passage of anadromous fish (such as salmon). The program was funded at an annual average of $200 million in multiyear appropriations and authorized at $800 million annually, subject to appropriations.

Annual Appropriated Funds

From FY2018 through FY2026, Congress appropriated funding for bridges outside the authorization process (Table 3). This annual appropriation of funds has continued through the period covered by the IIJA. In total, over the nine fiscal years from FY2018 through FY2026, about $5.7 billion was appropriated, an annual average of $633 million (in nominal dollars). Some of these funds were for a competitive bridge program for states with a population density of 100 or fewer per square mile (e.g., Consolidated Appropriations Act, 2018 [P.L. 115-141]). Other amounts were distributed by formula to states for which the percentage of total bridge deck area classified as poor was at least 7.5% (e.g., Consolidated Appropriations Act, 2019 [P.L. 116-6]).²⁹ For these years, Congress in effect pursued a two-pronged approach by making bridges eligible for funding at state discretion under the large highway formula programs established in authorization acts and supplementing these funds with targeted bridge funding in annual appropriations acts.

Bridge Spending History, FY2016-FY2025

Adjusted for inflation, average annual bridge spending (as measured by funding obligations) has been 22% higher in the IIJA period (FY2022-FY2025) to date than under the previous authorization law, the Fixing America's Surface Transportation Act (FAST Act; P.L. 114-94) as extended (FY2016 through FY2021). Average annual spending has been $12.0 billion in the IIJA period to date and $9.8 billion in the FAST Act period (FY2025 dollars). Programmatic funding sources have shifted from highway programs that states or grantees could also use to fund road projects, such as the Surface Transportation Program and the National Highway Performance Program, to other programs dedicated to bridge projects (Figure 2). For more detailed data, see Table A-2.

Figure 2. Trends in Federal Bridge Obligations by Program, FY2016-FY2025 (inflation-adjusted FY2025 dollars)

Source: Federal Highway Administration (FHWA). Notes: "Other" includes funding from the Bridge Formula Program and Bridge Investment Program. Inflation adjustment by CRS using Bureau of Economic Analysis, Price Indexes for Gross Government Fixed Investment by Type, National Income and Product Accounts Table 5.9.4, Line 40: State and local highways and streets. Weighted average used to approximate fiscal years.

Future Bridge Funding Needs

Every two years or so, FHWA assesses the condition and performance of the nation's highways and bridges, documents current spending by all levels of government, and estimates future spending needs to maintain or improve current conditions and performance.³⁰ As with any attempt to forecast future conditions, a host of simplifying assumptions, omissions, and data problems influence these estimates. Among other things, the estimates rely on forecasts of travel demand. Despite such uncertainties and assumptions, these estimates provide a way to assess the level of current spending compared with what would be needed in the future under different scenarios. Because of the modeling involved, FHWA's future needs estimates for bridges are limited to fixing deficiencies in existing bridges only when the benefits outweigh the costs.

The most recent assessment was published in 2024 based on 2014-2018 data. Represented in 2024 dollars, this assessment showed that an annual average of $20.4 billion was spent on bridge rehabilitation or replacement by governments at all levels from 2014 to 2018. An additional $1 billion-$2 billion per year was spent on the construction of new bridges.³¹ It estimated that fixing all bridge deficiencies existing in 2018 would cost $248 billion (in 2024 dollars). This figure is 12 times the level of spending on bridge rehabilitation and replacement in 2014-2018.³²

Of course, fixing all deficient bridges overnight is not feasible. FHWA, therefore, estimated how this investment backlog may change at various levels of spending during 2019-2038, taking into account the deterioration of existing bridges over that period. The results of this analysis are seen in Figure 3. FHWA estimated that eliminating the backlog by 2038 would require an investment of $28.9 billion annually (in 2024 dollars).

Figure 3. Estimated Effect of Various Spending Levels on Bridge Investment Backlog (average annual spending for 20 years)

Source: U.S. Department of Transportation, FHWA, and Federal Transit Administration, Status of the Nation's Highways, Bridges, and Transit: Conditions and Performance Report to Congress, 25th ed., 2024, exhibit 10-20, https://www.fhwa.dot.gov/policy/25cpr/. Notes: The current funding level is the annual average from 2014 to 2018, and the 20-year spending scenarios are for 2019 through 2038. CRS adjusted the data expressed in 2018 dollars to 2024 dollars using Bureau of Economic Analysis, Price Indexes for Gross Government Fixed Investment by Type, National Income and Product Accounts Table 5.9.4, Line 40: State and local highways and streets.

The IIJA provided an increase in federal highway funding overall and created new dedicated bridge funding programs (Table 2). If states were to commit the same amount of federal highway funding to bridges as they did in FY2022-FY2025, an average of about $11.7 billion annually (in 2024 dollars), total funding committed to bridges would be about $24.9 billion annually (in 2024 dollars). This assumes that state and local funds would continue to provide 53% of all bridge spending as has been the case in recent years.³³ If this funding level were to continue over 20 years, the bridge investment backlog would be reduced by about 90%, according to FHWA estimates. Additional funding would be needed for the construction of new bridges. As state and local governments make most of the decisions concerning which projects to pursue and, within the limits of federal matching share requirements, how much of their own money to commit, it is uncertain whether total bridge spending will achieve this level.

Issues for Congress

The IIJA replaced the former policy of gradual improvement of the nation's bridges with a more ambitious program to speed up the pace of bridge improvements. Evaluations of the implementation of this policy and its success in improving bridge conditions are likely to be of concern to Congress in a reauthorization of the surface transportation programs.

Bridge Funding Programs

The overall level of highway infrastructure funding and the amount dedicated to bridges by Congress is likely to be an issue in reauthorization of federal highway programs after the expiration of IIJA. IIJA created two new bridge funding programs and provided most of the funding as multiyear advanced appropriations from the Treasury general fund. Congress might decide to continue these programs with general funds or switch the funding source to the HTF. Alternatively, Congress might decide not to reauthorize these dedicated bridge programs, thereby allowing states to decide whether or not to use federal highway funds for bridge projects.

The collapse of the Francis Scott Key Bridge in Baltimore, MD, as a result of a vessel strike has highlighted the vulnerability of some bridges to cargo ships.³⁴ Although the cost of reducing these vulnerabilities to an acceptable level is unknown, anecdotal evidence suggests the cost might be high relative to current resources, especially resources available at the state and local levels. Congress could provide funding dedicated to reducing these vulnerabilities, either as a set-aside from existing bridge programs or as a new program. Another option is that Congress could require state and local bridge owners to reduce these vulnerabilities to an acceptable level with current federal and nonfederal funding.

Congress could consider whether the Harbor Maintenance Trust Fund (HMTF) is an appropriate funding source to provide navigation safety features at bridges in the navigation channel, such as dolphins or bumpers and fenders protecting bridge piers from vessel strikes.³⁵ Such projects would require an appropriation and legislative change in the types of projects supported by HMTF expenditures. These actions could be controversial because of their effect on the funding of existing types of projects that support HMTF taxpayers, primarily importers of waterborne cargo. Another issue might be the agency responsible for implementing navigation safety features at bridges. Many HMTF-funded projects—maintenance dredging, breakwater and jetty maintenance, and construction and operation of dredged material disposal facilities—are directly carried out by the Army Corps of Engineers.³⁶ By contrast, highway bridge projects, even if supported by federal funds, are typically carried out by state and local governments.

Type of Funding Distribution

Another potential issue could be the manner in which funding is distributed. In the IIJA, Congress created several competitive surface transportation funding programs, including one specifically for bridge projects. A rationale for these programs is to concentrate relatively large sums of funding on projects that may have significant national and regional benefits. In some cases, project sponsors have had difficulty funding these projects from federal formula funds, federal loans, and nonfederal sources. Consequently, some older and obsolete bridges have continued to serve vehicular traffic but less reliably and safely than might otherwise be possible.

Compared with formula funding, competitive funding places a greater administrative burden on project sponsors and is not guaranteed. Given the interest in "extra" federal funding among project sponsors, many applications are likely to be unsuccessful. For example, there were 33 eligible applications for large bridge funding under the FY2024 BIP. Of these 33 applications, FHWA recommended funding for 13 projects.³⁷

Nonfederal Funding for Bridges

Another criticism of federal funding, especially competitive funding, is that it may substitute for nonfederal funding. Thus, in some cases, for example, a large competitive federal grant might replace nonfederal funding, such as a new or higher user fee. Research by CBO has estimated that state and local governments that receive federal grants for highway projects "reduce their own per capita spending on highway capital by 26 cents for an additional dollar of annual federal formula grants."³⁸ This raises the possibility that more federal funding will lead to less combined state and federal spending on highway bridges than previous state and local spending patterns imply. Furthermore, given the large increase in bridge spending from bridge-only programs, states may choose to rely mainly on BFP and BIP to fund bridge projects and use a greater share of their core formula funds on non-bridge highway projects. This could result in the net increase in spending on bridges being less than Congress may have intended.

Possible options for Congress include imposing maintenance-of-effort requirements on bridge spending, although these would reduce funding flexibility at the state and local level, and can be difficult to enforce.³⁹ Another option for Congress is to lower the maximum federal share of bridge project funding. The maximum federal share for a large bridge project (defined as a project of $100 million or more) in the BIP was 50%, lower than for most highway and bridge projects administered by FHWA. A relatively low matching share could inhibit state and local governments from pursuing bridge projects.

Another consideration is the effect of federal funding on the use by state and local governments of bridge tolling. Wider use of tolling could allow for more rapid improvement of major bridges. Heavily traveled bridges can be attractive targets for conversion to toll facilities—many bridges have no convenient alternatives, so drivers may find it difficult to avoid paying whatever toll is imposed. In some cases, tolling authorities offer relief for certain drivers, such as those with income below a certain threshold.⁴⁰ The revenue stream provided by tolls can make bridge building and reconstruction an attractive investment for private entities that are interested in participating in a public-private partnership. Tolling can also help projects become eligible for a TIFIA loan that requires a dedicated revenue stream for repayment.⁴¹ Currently, any toll-free federal-aid highway bridge may be converted to tolling and receive federal highway aid if the conversion is related to the reconstruction or replacement of the bridge. Also, new bridges may be tolled.⁴²

The large increase in bridge funding could on the one hand lessen the use of tolling as a financing option, given that bridge tolls are often unpopular. On the other hand, the IIJA provided $50 million annually to the Congestion Relief Program for congestion solutions, including the imposition of tolls for congestion pricing. Congress may want to consider how federal funding programs affected the use of tolls to fund construction or reconstruction of bridges.

Spending on Off-System Bridges

Historically, nearly all federal highway funding was restricted to roads and bridges on the federal-aid highway system. Highway bridges have been the main exception to the rule. A minimum level of spending on off-system bridges, which typically carry much less traffic than bridges on the federal-aid system, has been required in every highway authorization bill since 1978.

Congress's interest in funding off-system bridges was affirmed under the IIJA. The existing off-system bridge spending requirements were continued and the set-aside for off-system projects has been strongly supported by predominantly rural states and by many county and municipal governments. The policy could be an issue if it constrains resources available to repair or replace more heavily traveled bridges on major roads.

Appendix.

Robert S. Kirk, retired CRS Specialist in Transportation Policy, contributed to an earlier version of this report.

Footnotes