Federal programs for bridge construction, reconstruction, and repair are authorized in surface transportation acts. In 2012, MAP-21 consolidated a number of existing highway formula programs, including the Highway Bridge Program (HBP). Bridge projects are now generally funded through the National Highway Performance Program (NHPP) and the Surface Transportation Block Grant Program (STBGP). MAP-21 included a number of statutory requirements related to transforming the surface transportation system to a performance-based approach. For instance, MAP-21 directed DOT to establish performance measures related to highway safety, asset condition, and highway system performance, among other things. In some cases, MAP-21 required DOT to use the rulemaking process to implement performance-based requirements. In 2015, the Fixing America's Surface Transportation Act (FAST Act), which reauthorized surface transportation programs, largely maintained current program structures, including MAP-21's overall performance- management approach. The FAST Act also expanded the eligibility of NHPP funds to be used for reconstruction, resurfacing, restoration, rehabilitation, or preservation of a non-National Highway System (non- NHS) bridge if the bridge is on a Federal-aid highway. FHWA is the agency charged with oversight of the condition of the nation's bridges. FHWA administers the federal-aid highway program that provides about $40 billion each year to states to design, construct, and preserve the nation's roadway and bridge infrastructure. These funds are distributed through annual apportionments established by statutory formulas. FHWA oversees the federal-aid highway program primarily through its 52 Division Offices located in each state, D.C., and Puerto Rico. FHWA Division Offices have 10 to 61 staff each, depending on the size of the state's highway program and other factors. As of June 2016, FHWA had approximately 2,800 staff--about two-thirds in the field and the remaining third at FHWA headquarters. FHWA distributes and tracks federal funds for highway and bridge projects and collects some data to estimate annual spending by state and local governments on highway and bridge projects. Specifically, FHWA tracks federal-aid highway program obligations in FMIS, for individual project segments or contracts. This allows FHWA to collect and report information on the types of activities (such as obligations for the construction of new bridges) funded with Highway Trust Fund monies. Although federal funding is provided to states to help improve highway infrastructure, state and local agencies own and maintain most of the nation's bridges. State and local agencies typically provide matching funds on bridge projects that receive federal funding and may contribute funds beyond their match amount. State-level DOTs are responsible for ensuring bridge inspections are completed and for inventorying bridges within their states according to federal standards (except for tribally or federally owned bridges). State DOTs and local-planning organizations have discretion in determining how to allocate available federal funds among various projects and are responsible for selecting highway projects, including bridge projects. FHWA collects some data to estimate annual spending by state and local governments on highway and bridge projects. Specifically, FHWA requests that state DOTs submit several forms to the Office of Transportation Policy Studies on a regular basis, such as: Form 532, State Highway Expenditures--submitted annually, it requests the total spent on all highways by the state, including bridges; bridges are not separately reported. Form 536, Local Highway Finance Report--submitted biennially, it requests the total spent on all highways by all units of the state's local governments. Bridges are not separately reported. Acknowledging difficulties in obtaining data from local agencies, FHWA recommends that states use sampling and estimation to prepare this form, such as collecting data from a selection of local governments and then expanding the sample to generate statewide totals. Form 534, State Highway Capital Outlay and Maintenance Expenditures--submitted annually, it requests bridge-specific and other highway outlays. This form is designed to complement the data in Form 532 by classifying the highway expenditures of states into improvement types, such as new construction and rehabilitation, among other things. As part of its oversight role, FHWA collects information from states on bridge conditions and maintains this data in its NBI database. Bridges that receive low inspection ratings on specific bridge elements are classified as deficient. Bridges may be classified as deficient for one of two reasons: A structurally deficient bridge has one or more structural components, such as the deck that directly carries vehicles, in poor condition. Structurally deficient bridges often require maintenance and repair to remain in service. A functionally obsolete bridge has a configuration or design that may no longer be adequate for the traffic it serves, such as being too narrow or having inadequate overhead clearance. Functionally obsolete bridges do not necessarily require repair to remain in service. A bridge that is both structurally deficient and functionally obsolete is listed as structurally deficient in the NBI. In this report, we assess the conditions of bridges classified as structurally deficient by both the total deck area and number of bridges. Analysis of conditions based on the total number of bridges without considering the size of bridges can create an incomplete picture. A state may have a large number of deficient bridges, but if the deficient bridges are small bridges, the total deck area in need could still be relatively low. In comparison, another state could have very few deficient bridges, but if those deficient bridges are large, the total deck area in need could be much higher. Bridges may vary significantly in size and generally, the needs of larger bridges are more costly than those of smaller bridges. Measuring the total deck area, which accounts for the size of a bridge, provides more information than counting the number of bridges (see fig. 1). We found that bridge conditions, as indicated by data in the NBI, have improved nationwide over the past 10 years, as measured by total deck area and number of bridges that are structurally deficient. The percentage of structurally deficient deck area and bridges declined along the same trajectory from 2006 to 2015. Specifically, the deck area on bridges classified as structurally deficient decreased from 9 percent to 7 percent, and over the same time period, structurally deficient bridges, by number of bridges, decreased from 13 percent to 10 percent (see fig. 2). Bridge owners have broad discretion in determining how to address bridge needs, but statutory requirements enacted in 2012 directed that states allocate some federal funds to bridges if states do not meet specified standards. FHWA does not issue guidance on which bridges to target with federal funds, such as specifically targeting structurally deficient bridges. However, MAP-21 contained a penalty provision where any state whose percentage of total deck area of bridges on the NHS classified as structurally deficient exceeds 10 percent for 3 years in a row must devote funds (equal to 50 percent of the state's fiscal year 2009 HBP apportionment) to eligible projects on bridges on the NHS until they meet this minimum threshold. FHWA officials told us they plan to use bridge condition data from 2014 through 2016 to determine if a penalty is to be applied to the states, and begin imposing this penalty in 2017 if needed. Despite overall improvements, among states there is variation in bridge conditions. Specifically, our review of 2015 NBI data shows that some states have substantially higher percentages of deck area on bridges classified as structurally deficient than others have (see fig. 3). For example, 21 percent of the total deck area in Rhode Island, affecting 23 percent of the 766 bridges in the state, is structurally deficient. While in Texas, less than 2 percent of the total deck area, affecting less than 2 percent of the state's 53,209 bridges, is structurally deficient. Most but not all states have made some improvements in reducing their percentage of deck area on bridges classified as structurally deficient over the past 10 years. Forty-one states, D.C., and Puerto Rico reduced the percentage from 2006 to 2015. Rhode Island had the greatest reduction, going from over 40 percent to over 20 percent of total deck area on bridges that are structurally deficient. However, in 9 states the percentage increased from 2006 to 2015. Delaware had the highest increase in the percentage of deck area on bridges classified as structurally deficient, going from 2 percent to almost 6 percent. GAO has reported that reducing structurally deficient bridges may not always be a state's highest priority. For example, a state may have other priorities for bridge projects such as seismic retrofitting. According to AASHTO representatives, states use their judgment in deciding how to prioritize their funding for bridge projects. See appendix II for more information about the percentages of bridges and total deck area that are structurally deficient in each state. The number of bridges and amount of total deck area increased dramatically from the 1950s through 1970s. The average age of bridges nationwide is 45 years, based on our analysis of NBI data. According to FHWA, the design life of the majority of existing bridges is 50 years, though bridges have life spans that are dependent on factors such as materials, environment, level of use, and level of maintenance. Also according to FHWA, new design guidelines and construction materials may raise the expected service life of new bridges to 75 years or longer. However, states and other bridge owners are faced with significant challenges in addressing the needs of existing bridges. In the 1950s, at the beginning of the Interstate-era, through the 1970s, the number of bridges constructed in the United States as well as the total square footage of bridge deck constructed increased greatly (see fig. 4). Analysis of NBI data indicates that the large number of bridges built during that time has led to an increase in the need to address those bridges that are now structurally deficient. Specifically, as shown in figure 5, the levels of structurally deficient total deck area are greatest for those built from 1960 through 1974, during which years the total deck area of bridges built in the United States peaked. The increased total deck area of bridges built after the 1950s suggest that an increase in bridges with structural deficiency may be expected and thus would increase the need for bridge maintenance, replacement, or rehabilitation. Federal funds obligated for bridges have remained relatively stable over the last 10 years, between $6 billion and $7 billion annually in most years (see table 1). However, total federal obligations for bridges were notably higher in 2 years (2009 to 2010) due to an influx of funds from the American Recovery and Reinvestment Act of 2009 (Recovery Act). Prior to 2013, the majority of obligations for bridges came from the HBP. Since 2013, such obligations have mostly come from the NHPP and STP. In the last 10 years, federal obligations have shifted somewhat from building new bridges to projects that preserve existing bridges. Based on our analysis comparing 2006 to 2015 obligations, the types of improvements made to bridges have somewhat changed (see fig. 6). For example, fewer federal obligations were directed to bridge replacements in 2015 than in 2006 (decreasing from 57 percent in 2006 to 48 percent in 2015). Also, fewer obligations went toward new bridges in 2015 than in 2006 (from 15 percent to 13 percent). Additionally, more obligations went toward bridge rehabilitation work--major work required to restore the structural integrity of a bridge or necessary to correct major safety defects--in 2015 than in 2006 (this increased from 23 percent of obligations in 2006 to 28 percent in 2015). Finally, the percentage of obligations used for preventative maintenance increased from 2006 to 2015 (from 6 percent to 11 percent). This is partly because more preventative maintenance activities such as bridge cleaning, painting steel bridges, sealing concrete, and repairing or replacing deck joints, became eligible for federal bridge program funding in 2006. Based on data collected from state and local governments, FHWA reported that total estimated spending on bridges increased in recent years, from about $11.5 billion in 2006 up to about $17.5 billion in 2012 (see table 2). Analysis of this FHWA data suggests that state and local funding for bridges has increased. FHWA tracks both the condition of bridges and the funding targeted to them, as described below. As part of its oversight role, FHWA seeks to ensure that states comply with the NBIS, which details the process for and frequency of bridge inspections. FHWA also collects bridge condition data from states and maintains the NBI, the primary source of information on the nation's bridges. The NBI contains information on each bridge, such as its location, size, age, condition, and inspection dates. FHWA (1) maintains data on total federal obligations dedicated to bridges each year; (2) periodically estimates the contributions from state and local agencies through data collection efforts; and (3) periodically reports to Congress its estimates of total funds dedicated to bridges (including state and local funds) in its Conditions & Performance Report, issued roughly every 2 years. The report also estimates future-spending needs to maintain or improve current conditions and performance. However, FHWA currently lacks a mechanism for tracking the relationship between the invested funds and the corresponding outcomes-- maintained and improved bridge conditions. Given that FHWA already estimates total funds dedicated to bridges and collects data on bridge conditions nationwide, it has the information needed to create performance measures that would demonstrate the link between federal funding and the outcomes for bridges. According to leading practices for government management identified by OMB and GAO, agencies should not only have and report performance measures but also use them to link outcomes with resources invested. Specifically, the Government Performance and Results Act (GPRA) of 1993 and the GPRA Modernization Act of 2010 establish the framework for performance management in the federal government. Under this framework, federal agencies are required to, among other things, assess whether relevant programs and activities are contributing as planned to established goals. Further, MAP-21 included a declaration on the importance of accountability and linking performance outcomes to investment decisions. We have reported that linking performance outcomes with information on resources invested (i.e., data on the resources used to produce an outcome, including costs) can help agencies to more clearly understand how changes in invested resources may result in changes to performance. We have also reported that an effective way to show the relationship between resources invested and outcomes is for agencies to use efficiency measures. These measures are typically defined as the ratio of two elements: a program's inputs (such as its costs or hours worked by staff), to its outputs or outcomes (see fig. 7). OMB has issued guidance with examples of meaningful performance measures, including some efficiency measures: for the Forest Service, cost per acre of environmentally important forest protected (provides costs per acre, including actual program obligations and other dedicated funds); for the Patent and Trade Office, cost per patent processed (provides costs per patent, including staff expenses and overhead costs); and for the Office of Child Support Enforcement, total child support dollars collected per dollar of program expenditures (provides outcomes-- dollars in child support collected--per total administrative expenditures including staff expenses). However, determining inputs--or invested resources--for efficiency measures can be challenging when there are non-federal entities contributing resources. Despite the usefulness of efficiency measures, we have acknowledged that many of the outcomes for which federal programs are responsible are part of broader efforts involving federal, state, local, and other partners, and thus it can be difficult to isolate a particular federal program's contribution to the broader outcomes. This is the case for highway programs, since funds from federal, state and local sources all contribute to maintained or improved asset conditions. However, federal guidance exists that may help. To assist agencies in implementing the GPRA framework, OMB issued guidance about how federal agencies might address the challenge of developing performance measures for programs that co-mingle funds from different sources (i.e., federal, state, and local funds) in support of a broad goal. The guidance acknowledged that it can be difficult to assess the marginal impact of the federal investment for programs where combined co-mingled funding contributes to the same broad performance outcome, but recommended that agencies should nonetheless seek to assess the marginal impact of the federal investment to the overall outcomes. OMB guidance noted that in such cases, the resource inputs from non-federal partners may be relevant in assessing the effectiveness of programs matched by federal assistance. OMB suggested that in such cases, agencies should consider crafting two performance measures of efficiency: one measure reporting unit costs in terms of output per federal dollar spent and another measure reporting unit costs in terms of the output per combined dollars spent. FHWA officials told us that they have not developed measures linking resources to outcomes. This is mostly due to limitations of the previous version of their financial tracking system, FMIS. Specifically, officials explained that prior to the most recent version of FMIS (Version 5), which was launched in October 2015, data were collected on a project segment level that may have included multiple bridges. Thus, it was not possible to directly compare federal obligations on bridge projects to outcomes, in the form of bridge conditions found in the NBI. However, when asked, officials said that such a comparison could be possible with the newest version of FMIS by creating a connection between FMIS and the NBI and showing what happens to bridge conditions when federal obligations change over time. Using such performance measures would help FHWA to demonstrate the link between federal funding and outcomes for bridges. As FHWA has reported in recent budget requests, states face increasing challenges in finding sufficient funding for their infrastructure needs. In addition, as GAO has previously reported, bridge infrastructure--like most of the nation's physical infrastructure--is under strain. Steady increases in road usage, congestion, and the aging of the nation's bridges will likely continue to present challenges in the future. Most of the state government officials we interviewed reported that, consistent with FHWA data, bridge funding has been stable since the federal bridge program was consolidated into other programs in 2012. We interviewed officials from 24 states and D.C., and officials from 21 states and D.C. told us there had been no change in funding their bridge programs in the last 4 years. Officials from 3 states reported an overall increase in bridge funding since that time, although officials from 2 of those states indicated that the increase in bridge funding was not necessarily a result of federal changes. The general stability in bridge funding may be a result of the long time frame for programming bridge projects, which could create a lag in funding levels' response to policy changes. AASHTO representatives told us it is difficult to judge the impact of federal statutory changes on bridges because of the long-term nature of infrastructure projects. Ten states and D.C. provided us with examples of bridge-programming cycles of 5 years or greater. For example, Ohio DOT officials told us that they program their bridge projects 6 years into the future. Through this process, state officials determine their project needs and request a planned allocation for the 6th year of the funding cycle. With this type of long-term planning and budgeting process, it may take several years for a change in federal policy to have a noticeable effect on bridge projects' funding. Officials from some selected states reported increased flexibility in their ability to use federal funds for bridges. In addition to allowing states the flexibility to determine whether to spend federal highway funds on bridges or other highway needs, changes provided by MAP-21 gave states flexibility to use federal funds for a greater range of bridge projects. Prior to MAP-21, only bridges that met certain criteria--such as being rated below a certain threshold or not having received federal funds in the previous 10 years--could receive federal funds. Officials from 10 of the 24 states and D.C. mentioned the increased flexibility in using highway funds for bridge projects since MAP-21. See table 3 for examples of how states used the increased flexibility. Officials from most selected states told us there have been no changes in prioritizing bridges relative to other transportation assets. Specifically, officials from 18 states and D.C. reported that they give bridges the same priority as they did prior to MAP-21. Officials from several of these states said that bridges have remained a high priority because of safety concerns. For example, an official from the New York DOT said that there is a keen awareness of what happens when bridges are not maintained, citing the state's major bridge failures in the 1980s--the Mianus River Bridge in 1983 and the Schoharie Creek Bridge in 1987, and thus bridges have remained a priority over time in New York. Though most states have reportedly not changed the way they prioritize bridges, officials from 2 states told us that bridges' relative priority may change after they implement performance management principles. For example, California officials told us they are transitioning toward a performance-based management approach where the needs of different transportation assets, including bridges and pavement, will be weighed against each other in order to meet performance targets within budgetary constraints. According to officials, a possible outcome is that local agencies in California may need more funding to repair their pavement or other assets to meet performance targets, which have yet to be determined through the FHWA rulemaking process on performance measures that is under way. Further, officials stated that these changes could have an impact on future bridge funding and relative priority. Likewise in Iowa, officials said that the state is moving toward using asset management principles in future decision making, which will involve more comparisons across different types of projects. Officials from a majority of the states and local agencies we interviewed cited inadequate funding as a challenge for their bridge programs. Of the officials we interviewed from 24 states and D.C., officials from 14 described inadequate funding as a challenge. See table 4 for examples of challenges of inadequate bridge funding cited. Local agency officials also discussed inadequate funding as a challenge for their bridge programs. Officials from 6 of the 10 local agencies we interviewed mentioned that inadequate funding for bridges was a challenge. For example, officials at the Oklahoma City Department of Public Works reported that many needed bridge projects are delayed because they lack sufficient funds. Further, they are only able to address the most critical needs due to limited funding. Transportation officials in Seattle, Washington, told us that the state DOT distributes a total of about $35 million per year in federal funds to local agencies, which compete for a part of those funds; however, the city's highest priority bridge has a replacement cost of about $350 million, which far surpasses what they may receive. Given the gap in funding for large projects, officials said they will be forced to close large bridges that are deemed unsafe if they are unable to raise the funds needed to repair them. Some state and local officials reported that many bridges are reaching the end of their intended service life. According to officials from several states and local agencies, most bridges were designed to last 50 years. Officials from 13 of the states we interviewed reported aging bridges as a challenge. For many of these states, the challenge of aging bridges is intertwined with the challenge of inadequate funds. State DOT officials stated that aging bridges require more costly maintenance and repairs and many need to be replaced. See table 5 for examples of challenges cited related to aging bridge inventories. Other challenges were also cited by state DOT officials. See table 6 for examples of challenges that were less frequently stated. Bridge conditions have generally improved nationwide over the past decade. However the increase in the number and size of bridges that are approaching the limits of their design life will likely place a greater demand on bridge owners in the near future, making it more difficult to mitigate issues in a cost-effective manner. While FHWA collects information on bridge conditions annually and maintains data on federal obligations dedicated to bridges, it lacks performance measures demonstrating the link between bridge funding and changes in bridge conditions. This lack is in part because a limitation in the prior financial- tracking system, which did not allow the direct comparison of federal obligations with bridge projects' outcomes. However, with recent improvements to FMIS, FHWA has the information needed to create an efficiency measure or measures to demonstrate the link between federal funding and the outcomes for bridges. This information can support Congress in making informed choices about how to best invest the limited available resources in maintaining or improving the condition of the nation's bridges. We recommend that the Secretary of the Department of Transportation direct the FHWA Administrator to develop an efficiency measure or measures that demonstrate the linkage between the federal funding of bridges and the desired performance outcomes, such as maintained or improved bridge conditions, and report the resulting information to Congress. We provided a draft of this report to DOT for its review and comment. In written comments, reproduced in appendix III, DOT concurred with our recommendation. In addition, DOT provided technical comments that we incorporated as appropriate. We are sending copies of this report to appropriate congressional committees and the Secretary of Transportation. In addition, the report is available at no charge on the GAO website at http://www.gao.gov. If you or your staff have any questions about this report, please contact me at (202) 512-2834 or Goldsteinm@gao.gov. Contact points for our Offices of Congressional Relations and Public Affairs may be found on the last page of this statement. The names of GAO staff who made key contributions to this report are listed in appendix IV. This report addresses the funding and management of bridges and examines: (1) trends, over the past 10 years, in the condition of the nation's bridges; (2) trends, over the same period, in federal funding of the nation's bridges and how FHWA monitors the linkage between this funding and outcomes; and (3) changes since MAP-21 in how selected states fund and manage their bridge programs, including any challenges they face. To determine trends in the condition of the nation's bridges, we reviewed and analyzed FHWA's National Bridge Inventory (NBI) data from calendar years 2006 through 2015. We limited our review of NBI data to bridges that are located on public roads and that are at least 20 feet in length. We obtained NBI data for bridges during the selected calendar years for an aggregate of all records and by state, including all 50 states; District of Columbia (D.C.); and Puerto Rico. Specifically, we reviewed data by number of bridges and total deck area, looking at deficiency status and year of bridge construction, among other data. We calculated total deck area based on a formula using structure length and deck width--or in the case of culverts (structures with fill over them), approach roadway width-- using NBI data. To determine trends in funding the nation's bridges, we reviewed and analyzed federal obligations data on bridge projects in FHWA's Fiscal Management Information System (FMIS) from fiscal years 2006 through 2015. Specifically, we obtained federal obligations data for bridge new construction, bridge replacement, bridge rehabilitation, bridge preventative maintenance, bridge protection, and bridge inspection and related training. We analyzed the data by improvement codes and by federal highway programs. In addition, we analyzed FHWA's available data on state and local governments' spending for bridge projects by reviewing data from the 2013 FHWA Conditions and Performance Report, reviewing FHWA's Highway Statistics Series of reports, and interviewing FHWA officials. We assessed the reliability of the data that we used by reviewing documentation and interviewing officials on data verification and found the data to be reliable for our purposes. We also reviewed Office of Management and Budget (OMB) guidance and leading practices we have previously identified related to tracking, through performance measures, the linkage between funding and outcomes and compared current activities to this guidance and these leading practices. To determine how states fund and manage their bridge programs, including any challenges they face, we interviewed representatives from the American Association of State Highway and Transportation Officials and the National Association of County Engineers. We also interviewed state officials from 24 states and D.C. We selected this non-generalizable sample of states because they have large bridge inventories, relatively high levels of federal surface transportation funding, and for geographic dispersion. The selected states were: California, Connecticut, Florida, Hawaii, Illinois, Iowa, Kansas, Louisiana, Massachusetts, Michigan, Minnesota, Mississippi, Missouri, Nebraska, New York, Ohio, Oklahoma, Oregon, Pennsylvania, Rhode Island, South Dakota, Texas, Vermont, and Washington. From the selected states, we further selected 5 states for site visits, based on selection criteria similar to that stated above, in order to obtain additional information from each state. We selected California, Oklahoma, Rhode Island, Texas, and Washington for site visits. In these states, we met with state transportation officials, FHWA Division Office officials, and officials from two local-government transportation agencies from each state. We selected the non- generalizable sample of local agencies based on recommendations from state officials of nearby local agencies that could accommodate our site visit schedule. The selected local agencies were: Los Angeles County (California); Placer County (California); City of Oklahoma City; Oklahoma Cooperative Circuit Engineering District #7; City of Providence (Rhode Island); Rhode Island Turnpike and Bridge Authority; City of Austin (Texas); Williamson County (Texas); King County (Washington); and City of Seattle (Washington). In addition to the individual named above, Heather MacLeod, Assistant Director, Jessica Bryant-Bertail, Brian Chung, Danielle Ellingston, Dave Hooper, Ying Long, SaraAnn Moessbauer, Josh Ormond, and Amy Rosewarne made key contributions to this report.

Summary:
The nation's 612,000 bridges are critical elements of the surface transportation system, but the entire system is under growing strain and funding it is on GAO's High Risk List. While state and local governments own and maintain most of the nation's bridges, the federal government provides some funding for them, administered by FHWA. In 2012, legislative changes consolidated the bridge-funding program into other highway programs, giving states more flexibility in how to allocate funds. GAO was asked to review the funding and management of bridges. This report examines trends, over the past 10 years, in (1) the condition and (2) the funding of the nation's bridges, as well as (3) how states fund and manage their bridge programs, given the 2012 legislative changes. GAO analyzed FHWA's bridge conditions and funding data; reviewed applicable laws, relevant FHWA program guidance, and federal guidance on performance measures; and interviewed federal officials and transportation officials from 24 states and D.C., selected to include those with large bridge inventories, among other factors. Bridge conditions have generally improved nationwide from 2006 to 2015, based on GAO analysis of federal bridge data. For example, the percentage of structurally deficient bridge deck area (the surface area that carries vehicles) decreased from 9 percent to 7 percent nationwide during this period. The number of structurally deficient bridges also decreased from 13 percent to 10 percent nationwide. However, some states have substantially higher percentages of structurally deficient deck area than others. Bridge conditions may become more challenging to address as bridges age, because the number of bridges and amount of total deck area increased dramatically from the 1950s through the 1970s, generally with a 50-year design life. Analysis of federal bridge data shows that the amount of structurally deficient deck area is greatest for bridges built from 1960 through 1974, indicating an expected need for additional maintenance, replacement, or rehabilitation. Federal funds obligated for bridge projects have remained relatively stable from 2006 to 2015, between $6 billion and $7 billion annually in most years. During this period, the use of federal funds on bridges shifted somewhat from building new bridges to projects that preserve existing bridges, such as bridge rehabilitation or preventative maintenance. While the Federal Highway Administration (FHWA) estimates total funds dedicated to bridges and collects data on bridge conditions nationwide, it does not track the linkage between federal funds and changes in bridge conditions. GAO has previously reported that linking performance outcomes with resources invested can help agencies to more clearly determine how changes in invested resources may result in changes to performance. Using such performance measures would help FHWA demonstrate the link between federal funding and outcomes for bridges. Officials from the selected 24 states and the District of Columbia (D.C.) reported little change in the way they have funded and managed bridges since 2012. Officials from 21 states and D.C. reported bridge funding has been stable since the federal bridge program was consolidated in 2012. Officials from 3 states reported an increase in bridge funding since that time. The general stability in bridge funding may be a result of the long time frame for planning bridge projects; for example, bridge funding cycles can be 5 years or longer, a time span that means any changes would not be apparent for several years. Officials from 10 states mentioned increased flexibility in their ability to use federal funds for bridge projects. Changes from the Moving Ahead for Progress in the 21st Century Act provided states flexibility to determine whether to spend federal highway funds on bridges or other highway needs. Further, officials from 18 states and D.C. reported that they have not changed how they prioritize bridge projects relative to other transportation projects. With respect to challenges, officials from 14 states described inadequate funding as a challenge, and officials from 13 states reported aging bridges as a challenge. For many of these states, the challenge of maintaining aging bridges is intertwined with the challenge of inadequate funds. GAO recommends that DOT direct FHWA to develop measures on the linkage between the federal funding of bridges and the desired outcomes--maintained or improved bridge conditions--and report results to Congress. DOT concurred with our recommendation. DOT also provided technical comments, which we incorporated, as appropriate.