Bridge safety first emerged as a high-priority issue in the United States in the 1960s, following the collapse of the Silver Bridge between Ohio and West Virginia, which killed 46 people. That collapse prompted national concerns about bridge conditions and safety and highlighted the need to repair and replace bridges before they collapse. Congress responded by establishing two major federal bridge programs: (1) the National Bridge Inspection Program (NBIP) to ensure periodic safety inspection of bridges and (2) what is now known as the HBP to provide a funding mechanism to assist states in replacing and rehabilitating bridges. Both of these programs generally define applicable bridges as publicly owned, over 20 feet in length, and located on public roads. Although the NBIP and HBP are separate programs, they are linked by the data collected through bridge inspections. For example, bridge information gathered through NBIP inspections is one factor used to determine the amount of HBP funding apportioned to states. The NBIP establishes federal standards, known as the National Bridge Inspection Standards, and program requirements for the proper safety inspection and evaluation of bridges. These standards establish by whom, with what frequency, and how bridge inspections are to be completed. For example, state departments of transportation (DOTs) carry out the federal- level policies, procedures, and requirements for inventory, inspection, bridge load ratings, quality assurance, and reports. Routine bridge inspections are generally conducted every 2 years, but with FHWA approval, the inspection interval may be extended to 4 years on certain bridges. Bridges may be inspected more often than every 2 years, when past inspection findings justify an increased inspection frequency. Bridge inspectors must record bridge data, including bridge conditions, during the inspection and report that information to the NBI, maintained by FHWA headquarters. Based on information gathered during bridge inspections and reported to the NBI, the HBP classifies bridge conditions as deficient or not; assigns each bridge a sufficiency rating reflecting its structural adequacy, safety, serviceability, and relative importance; and uses that information to provide funding for states to improve bridges. Deficient bridges include those that are structurally deficient, with one or more components in poor condition, and those that are functionally obsolete, with a poor configuration or design that may no longer be adequate for the traffic they serve. FHWA uses information in the NBI to annually apportion HBP funds to the states. While each state’s HBP apportionment amount is largely determined by bridge conditions and bridges generally must be below a certain condition threshold to qualify for HBP funding, other bridges are also eligible for HBP funds because states may use the funds for a broad array of other purposes, such as bridge preventive maintenance projects. All bridges are grouped into one of two general categories: Federal-aid highway bridges and bridges not on Federal-aid highways. The NBIP and the HBP generally apply to both categories of bridges located on public roads. Federal-aid highway bridges are generally located on the National Highway System, a 160,000–mile network that carries over 40 percent of the nation’s highway traffic. Non-Federal-aid highway bridges are generally located on local or rural roads that carry lower volumes of traffic than state-owned bridges. The HBP affords state DOTs discretion in determining how to use their HBP funds, and as a result, states use HBP funds and select bridge projects in a variety of ways. The HBP gives states three key flexibilities in determining how to use their HBP resources. First, the HBP has evolved to allow states to use program funds not only for bridge replacement and rehabilitation, but also for a broad array of purposes—including painting, seismic retrofitting, systematic preventive maintenance, installation of scour countermeasures (to address the effects of sediment erosion around bridge piers and abutments), and anti-icing or deicing applications— regardless of the bridge’s condition. In addition, FHWA has determined that the costs for personnel and equipment used in bridge inspections and for bridge management systems are consistent with the purpose of the HBP and therefore are also eligible uses for HBP funds. Thus, states have the flexibility to use HBP funds on bridge projects that may not immediately reduce their inventory of deficient bridges. Secondly, states have flexibility in determining how to split HBP resources between state and locally owned bridges. Aside from a requirement to distribute funds equitably, the only HBP requirement applicable to states’ allocation of program funds is that states must spend a minimum (15 percent) on non- Federal-aid highway bridges. Third, states may also spend program funds on other, nonbridge, transportation priorities by transferring up to 50 percent of their annual HBP funding to other core Federal-aid highway programs, though a penalty is invoked by reducing the state’s HBP funds in the succeeding year by the amount transferred. Many states have taken advantage of this provision over the years and transferred some of their HBP funding to other programs, although FHWA officials pointed out that some of the transferred HBP funds may still be spent on bridges and funds from other Federal-aid highway programs may also be spent on bridges. FHWA data show that significant funds have flowed toward bridges from other programs which, from a national perspective, exceed outflows from the HBP. Finally, planning for how HBP funds are spent is generally under the control of state DOTs; once states select bridge projects, they may apply to FHWA for the federal share of the costs, which is generally 80 percent of the project cost. In part due to these flexibilities, state DOTs we visited have established a range of priorities for their HBP funds—from reducing the number of their deficient bridges to seismically retrofitting their bridges—and some opted to transfer their HBP funds to fund other transportation priorities. Although the key purpose of the HBP is to enable states to improve the condition of their deficient bridges, some state transportation officials we interviewed explained that they do not focus on reducing their inventories of deficient bridges for several reasons: Deficient bridges are not necessarily unsafe. Many state transportation officials we interviewed told us that some of the deficient bridges in their states are in at least reasonably good condition and are safe. In addition, FHWA reported in 2007 that classifying a bridge as deficient does not immediately imply that it is likely to collapse or that it is unsafe. According to the FHWA report, if proper vehicle weight restrictions are posted and enforced, deficient bridges can continue to serve most traffic conditions. FHWA requires that bridge owners close to traffic any bridges that they determine to be unsafe. The HBP apportionment formula may create a disincentive to improve deficient bridges. Many federal and state officials we met with noted this potential disincentive that occurs because reducing the number and deck area of deficient bridges reduces a state’s HBP funding eligibility. Some deficient bridge projects can be cost-prohibitive. Some state officials explained that certain large-scale bridge projects—often the most traveled, urban bridges on interstate corridors—are too expensive to be implemented with HBP funds alone, especially costly “mega” projects that have an estimated total cost greater than $500 million. State DOTs use a variety of criteria, tools, and methods to select among potential bridge projects. Officials in the six states we visited use criteria such as bridge condition ratings, average daily traffic over bridges, local transportation priorities, or funding availability when prioritizing and selecting among potential bridge projects. Some states have also developed tools and approaches beyond those required by the HBP—such as bridge management systems, element-level inspections, state-specific condition ratings, and various prioritization approaches—to help them gauge bridge conditions and further inform their selection of bridge projects for funding. For example, all of the states we visited have adopted, or are considering, some form of bridge management system for gathering and analyzing bridge data to help manage their bridge assets and more efficiently allocate limited HBP resources among competing bridge priorities. States use these systems to predict future bridge conditions, estimate bridge maintenance and improvement needs, determine optimal policies for rehabilitation and replacement, and recommend projects and schedules within budget and policy constraints. FHWA has actively encouraged, but has not required, states to use bridge management systems, in part, by providing state transportation officials with relevant training and technical support. In addition, all of the states we visited required bridge inspectors to gather more detailed “element-level” bridge condition data, thereby exceeding the federal inspection requirements that require inspection of only the three major bridge components (superstructure, substructure, and deck). Furthermore, some state DOTs use their own bridge rating systems to better gauge bridge conditions and to inform their selection of bridge projects for funding. For example, the New York State DOT uses its own condition rating scale, which is based on an assessment of 47 individual bridge elements, to prioritize bridge projects. Finally, state DOTs use different methods to prioritize and select bridge projects for funding. Whereas some states we visited had highly centralized prioritization processes, others allowed the process to vary across the state. Bridge conditions, as measured by the number of deficient bridges and average sufficiency rating, improved from 1998 through 2007. According to NBI data, the total number of deficient bridges—including both structurally deficient and functionally obsolete bridges—has decreased over the last 10 years, even as the total number of bridges has increased. From 1998 through 2007, the number of deficient bridges declined by nearly 12 percent, from 172,683 to 152,317, even with the addition of more than 16,000 new bridges to the NBI (see fig. 1). The decline in the overall number of deficient bridges over the past decade reflects a reduction in the number of structurally deficient bridges. From 1998 through 2007, the number of structurally deficient bridges decreased by 22 percent, from 93,118 to 72,519 (see fig. 2). During that same period, the number of functionally obsolete bridges increased slightly from 79,565 to 79,798, an increase of 233 bridges.