The Federal-Aid Highway Act of 1944 established the Interstate Highway System but did not provide specific funding for construction. In the Federal-Aid Highway Act of 1956, Congress declared that the completion of a “National System of Interstate and Defense Highways” was essential to the national interest. The act called for new system design standards, began an accelerated construction program, established a new method for apportioning funds among states, and set the federal government’s cost share for Interstate construction projects at 90 percent. At the same time, the Highway Revenue Act of 1956 introduced a dedicated source for federal highway expenditures, providing that revenue from certain federal motor fuel and other motor vehicle related taxes be credited to the Highway Trust Fund. The federal government, from 1954 through 2001, invested over $370 billion on Interstates through apportionments to the states, more than on any other class of road. Today, FHWA, within DOT, administers a variety of federal highway programs supported by the trust fund—collectively referred to as the Federal-Aid Highway Program. The Interstate Highway System, as it came to be known, has particular design characteristics. Its roads are generally divided highways with at least four lanes of traffic and wide shoulders. The Interstate avoids intersections by having other roads pass over or under it, and it has access control—that is, vehicles generally join or leave the flow of traffic by a limited number of access or exit ramps. (See fig. 2.) Certain characteristics were meant to facilitate military movement, such as the requirement for 16 feet of clearance under bridges that pass over Interstate highways. A distinctive red, white, and blue shield denotes Interstate highways. The Interstate Highway System, as of 2000, extended over 46,000 miles in length and 209,655 lane miles. In 1991, Congress provided final funding for the completion of the Interstate System. From 1990 through 2000, Interstate mileage grew by about 3.1 percent, or 1,405 miles in length, or 11,491 lane miles during the decade. Growth occurred primarily in urban areas. Overall, urban mileage climbed by 1,885 miles, or 16.2 percent, during this period, while rural Interstate mileage declined by 480 miles, or 1.4 percent. (See fig. 3.) Some of the urban mileage gain occurred as new road mileage expanded the system. The rest occurred as urban boundaries grew to take in Interstate highway miles that were originally in rural areas. According to FHWA, Interstate highways are a principal part of an overall network of roads throughout the nation. The Interstate System composes 29 percent of the estimated 161,000-mile National Highway System (NHS) designated by Congress in 1995. The NHS also includes other arterial roads of national interest. The entire Interstate Highway System is also part of the Strategic Highway Network (STRAHNET), an approximately 61,000-mile network of roads designated as important to the U.S. military. Currently, both the federal government and states fund the construction and maintenance activities on the Interstate Highway System. Each year, billions of dollars are provided to the states for the construction and repair of highways through various highway programs. Under one such program—the Interstate Maintenance Program (IM)—federal funds support projects for resurfacing, restoring, rehabilitating, or reconstructing portions of the Interstate System. Those projects generally require a 10 percent state match, while projects on other classes of roads generally require a 20 percent match. Under certain circumstances, states may transfer funds among various highway programs. For example, subject to certain limitations, states may transfer IM funds to other programs and use them on other classes of roads (with a 20 percent match). Similarly, states may also transfer funds from other funding categories to their IM program and use them for qualifying projects on Interstate highways. The Interstate Maintenance Discretionary Program provides funding for the kinds of projects funded under the IM program. In addition, Bridge Discretionary Program funds can be used on Interstate bridges. FHWA solicits candidates for the discretionary programs and selects projects for funding from applications. Finally, the Highway Bridge Replacement and Rehabilitation Program provides funds for states to replace or rehabilitate deficient highway bridges located on any public road, including the Interstate System. In 1991, we reported on Interstate conditions. In that report, we raised concerns about the poor condition of Interstate highways and about FHWA’s oversight of them. Among other things, we suggested that the DOT report to Congress on the levels of investment required for Interstate maintenance and on the progress being made to achieve adequate maintenance. DOT included information in Appendix A of the 1999 Conditions and Performance Report that was partially responsive to this recommendation. According to state officials, the Interstate Highway System plays an important and expanding role in the country’s transportation system. The original purposes of the system were to provide for efficient long-distance travel, support defense requirements, and connect metropolitan and industrial areas. Most states agree that these roles continue to be important but emphasized that several additional important roles have emerged in recent years. For example, most state officials see the Interstates as increasingly supporting economic growth and moving freight, as well as getting passengers to airports and supporting urban travel. The Interstate Highway System was primarily developed to address (1) the public’s demand for efficient long-distance travel, (2) the needs of the military, and (3) the nation’s economic development through the connection of metropolitan and industrial areas. The expectations for the Interstate Highway System are described in the following sections. The public’s desire for easy long-distance travel manifested itself in the early 1900s through an increase in car ownership and a growing interest in cross-country travel. Along with this increase in vehicle ownership came a significant increase in travel and tourism, quickly making cross- country travel a major recreational activity for millions of Americans. The system allows the nation’s military a means to expeditiously reach military cross-country installations and ports for deployment. In 1922, the United States Army developed the “Pershing Map,” which illustrated for the first time the major roads of prime importance during times of war. Each of the routes that the Army identified in the map was included with those roads eligible for federal aid. The military importance of the Interstate System was emphasized in 1956 when legislation named the Interstate Highway System the National System of Interstate and Defense Highways. By connecting metropolitan and industrial areas, the Interstate System was also meant to promote the nation’s economic growth and development. Without an efficient, far reaching national highway system, merchants found it difficult to move their goods to market in a timely manner. The 1944 Interregional Highways report explained that the Interstate System was also intended to serve the nation’s economic needs in agricultural production, mineral production, forestry, and manufacturing centers. According to state officials, the previously mentioned roles continue to be important, but the role of the Interstate System in freight movement has increased significantly. State officials we spoke with said that the Interstate System plays a significant role in their economy by facilitating the movement of goods by truck. State officials are concerned about economic development in their states and see the Interstates, especially in terms of freight movement, as playing a significant role in economic development. In responding to our survey, officials reported that today, after affording safe transportation, the most important roles of the Interstates include moving freight and supporting economic development. (See fig. 4 for the number of states classifying the importance of different Interstate functions.) Officials from 33 states indicated that supporting their state’s general economic development is a very great role for the Interstate System. Officials from 35 states responded that moving freight through their state is a very great role for their Interstates, and 30 states believed that moving freight within their state is a very great role. According to state officials, moving freight on their Interstate System is an important focus of their transportation programs. For example, state of Florida transportation officials told us that although reducing congestion for cars is important, maintaining mobility for freight traffic on their Interstate System is very important for industries in their state. For example, three Interstate routes connect the state’s dairy industry with other areas of Florida, which consume 85 percent of the milk produced in the state. In addition, Ohio’s survey response indicated that the Interstate System was very important for moving freight. The state estimates that its Interstate and multilane freeway system currently carry about 85 percent of all the state’s freight and “Keeping the state’s Interstate ystem moving smoothly and freely is not only important to the economy of the state, but also to the nation’s economy.” The role of the Interstate System in carrying freight has increased significantly over the past 20 years. According to our survey results, 45 of the state departments of transportation reported that the role of the Interstate System in moving freight through their state had increased; officials from 43 states responded that the Interstates had a greater role moving freight within the state. Our nation’s freight is currently moving extensively by truck on the Interstate System, and this movement is important to economic development. The most recent U.S. Commodity Flow Survey (1997) reported that trucks carry over 69 percent of the tons shipped in the United States and 72 percent of the value of goods shipped in the country. In addition, truck traffic on the Interstates made up over 41 percent of total truck miles traveled in 2000. An FHWA report and a consultant’s report explain that freight movement has significantly contributed to improving the country’s economic efficiency and productivity by, among other things, making “just-in-time” delivery more feasible, thereby reducing warehouse and manufacturing costs. Officials from 39 states identified the Interstate System’s support of travel within metropolitan areas as a great or very great role. Officials from 33 of the states said that this role has become greater in the past 20 years. When the Interstate System was planned, it was expected to provide efficient travel through the country and to connect major metropolitan areas where feasible. However, according to FHWA, Congress never expected the Interstate System to accommodate local traffic. Now a number of trips on urban Interstates, such as commuting trips, are completed within an urban area, rather than going through or beyond the urban area. For example, while urban Interstates make up about 4 percent of all urban lane miles, they carry about 24 percent of all urban traffic. According to states, the Interstate System provides efficient urban travel, and as such, urban users want easy access to it. In addition, according to North Dakota officials, the urban area of Fargo, North Dakota has encompassed Interstate 29 and the Interstate is now sometimes used as a local street. Finally, some of the states that we surveyed said that Interstate highways are increasingly important for moving people to specific locations that may not have been seen as important when the Interstate was designed. For example, 30 states reported that moving people to airports is a greater or much greater role now than previously. Airport enplanements have grown rather steadily over the past 20 years—increasing by almost 129 percent from 1980 through 2000. Since establishing the Interstate Highway System, the federal government has provided both funding for and oversight of the system. While still providing funding for the system, the federal government’s oversight focus is currently on ensuring that states have the procedures in place to manage the Interstates, as well as providing some project-level oversight. State departments of transportation manage most of the “hands-on” work of constructing, maintaining, and planning for the future of the Interstate System. States also fund a portion of Interstate projects, though to a much smaller extent than the federal government. Congress, FHWA, and the Department of Defense (DOD) play important roles with respect to the Interstate Highway System, including funding and overseeing state planning activities, and financing the majority of construction and maintenance of the system. By passing authorization and appropriations legislation, Congress plays a significant role with respect to federal highway programs, including Interstate-related programs. Authorization legislation, such as the Intermodal Surface Transportation Efficiency Act of 1991(ISTEA) and the Transportation Equity Act for the 21st Century (TEA-21), enacted in 1998, provide funding for various highway programs and related activities, establish mechanisms for the distribution of those funds, and set forth eligibility requirements for the highway programs, including the Interstate programs, limiting how the funds made available may be used. Among other things, annual appropriation acts make amounts from the Highway Trust Fund available for payment of obligations incurred for various highway programs. Funding for the Interstate System has been a major part of total federal highway funding, since 1954, when federal funding for Interstate construction began. However, the proportion of apportionments to states, specifically for the Interstate activities, has decreased over time as compared with overall highway program apportionments. In 1960, the annual Interstate apportionment was $12.2 billion (in 2001 dollars), or 72.8 percent of that year’s federal highway apportionments to states. From 1954 through 1991, total apportionments for Interstate construction and preservation reached $331.2 billion, or 56.8 percent of federal highway funding apportioned to states for the period. From 1992 through 2001, Interstate highway apportionments were $39.1 billion, or 17.5 percent of funding apportioned to states. With ISTEA, Congress scaled back funding apportioned to states specifically for Interstate highways to $23.9 billion or 20.3 percent of federal highway apportionments from 1992 through 1997. In addition, Interstate apportionments were $15.2 billion, or 14.3 percent, of federal highway apportionments for the next 4 years under TEA-21. (See fig. 5.) ISTEA also created the NHS and the Surface Transportation Program. Those programs accounted for 18.0 percent and 21.8 percent, respectively, of the $223.8 billion in federal highway apportionments made to the states from 1992 through 2001. As Congress considers reauthorization of the surface transportation programs in 2003, it will face decisions about the continued level of federal involvement in managing and financing the Interstate System. Even after providing final funding for Interstate completion in 1991, Congress has continued to designate new Interstate routes. In 1991, Congress also found that the Interstate System, or comparable highways, did not adequately serve many of the nation’s regions and identified high- priority corridors for development on the NHS to help meet the demands for increased capacity. Since 1991, 43 of these high-priority corridors have been designated, 10 of which were designated to become part of the Interstate System. In addition, authorization and appropriations acts have designated funding specifically for certain identified high-priority projects, which may include improving access to Interstate highways, reconstructing Interstate interchanges, extending Interstate highways, or performing work on roads other than Interstates. FHWA’s role in managing the Interstate System has changed from project- specific oversight to primarily overseeing state processes and procedures and specific projects. While FHWA was heavily involved in selecting routes for the Interstate System, for overseeing their construction, and ensuring that the system was adequately maintained, much of the responsibility for managing them now falls to the states. FHWA is also responsible for overseeing certain high-cost projects on the Interstate System. FHWA reviews and approves project designs; approves plans, specifications, and estimates; concurs in contract awards; and inspects projects. Today, FHWA does not have significant responsibilities for Interstate maintenance. For about two decades—until 1998—each state was required by statute to annually certify that the Interstate highways in their state were being maintained in accordance with federal requirements. The law authorized sanctions against states that did not adequately maintain their Interstate highways; but, they were rarely applied. TEA-21 repealed the statutory provisions regarding maintenance certification in 1998. However, if FHWA finds that highways constructed with federal funds are not being properly maintained, it is required to inform the state and withhold federal approval of future state-highway projects in all or part of the state if the condition is not corrected within 90 days. Although construction of the Interstate System is essentially complete, the agency may approve additions to the existing Interstate Highway System when states request such an addition. When FHWA receives requests for additions to the existing system from states, it considers, among other things, whether the proposed new segment is a logical addition or connection to the Interstate System and whether it meets Interstate geometric and safety standards. Although both Congress and FHWA designate specific additions to the Interstates, the nation does not currently have a centralized system for determining whether new routes are needed and building them. Similarly, the agency approves adding access points (interchanges and ramps) to the existing system and system design exceptions. FHWA is also responsible for overseeing states’ planning processes by reviewing and approving statewide transportation improvement programs (STIPs). These federally required plans cover at least 3 years and describe the state’s planned construction, maintenance, and other highway projects, including Interstate projects. FHWA’s review of the STIP primarily focuses on whether the required processes were followed rather than on the content of the plan. (See app. III for more details about the planning process.) FHWA also has other responsibilities related to the Interstate System. For example, the agency sets performance goals, as required by the Government Performance and Results Act of 1993 (Results Act), for pavement quality, bridge condition, highway congestion, and safety. Although FHWA does not have Interstate-specific performance goals, its performance goals do include Interstate highways. For example, FHWA’s safety goal is to reduce highway fatalities and injuries by 20 percent by 2008. FHWA’s performance goal for pavement quality applies to the NHS, which includes the entire Interstate System. These are FHWA’s goals, and states are not required to meet them for their Interstates or other roads. Finally, other FHWA responsibilities include providing technical assistance and management tools, such as investment-analysis models, to aid in the planning process at state transportation agencies; conducting transportation-related research; and disseminating the results throughout the country. DOD played an important role in establishing the Interstate Highway System. However, state officials reported that this role has not increased significantly in the past 20 years. DOD participated in selecting the Interstate highway routes, and according to DOD and FHWA officials, DOD works with federal and state transportation officials to ensure that the Interstate System meets its national defense requirements. In 1981, DOD, in partnership with FHWA, identified public highways to make up the STRAHNET. This network of highways gives the military the ability to move equipment and personnel expeditiously over the highway system from military installations to ports for deployment. The STRAHNET consists of 61,044 miles plus 1,700 miles of connectors that link over 200 important military installations and ports to the network. All of the nation’s Interstate highways are included in the STRAHNET. STRAHNET and its major connectors were incorporated into the NHS in 1995. This continues to emphasize the military importance of these highways. According to DOD officials, the working relationship between DOD and FHWA, and the conditions on the Interstate System, are adequate. States handle many of the responsibilities for managing the Interstates as well as providing some funding. State responsibilities include developing plans for maintaining the physical and operational conditions and the safety of Interstate highways. States are required to develop at least two planning documents—a 20-year Statewide Transportation Plan and a short- term Statewide Transportation Improvement Program (STIP) that covers at least 3 years. The plans outline how the states will use available funds to maintain the physical and operational conditions and the safety of their Interstates. To develop these planning documents and maintain their Interstates, states use a variety of approaches. See appendix III for a description of states’ planning processes. In addition, state departments of transportation are responsible for the day-to-day operations of constructing and maintaining the Interstates. Finally, state governments provide some funding for the Interstate Highway System; however, they spend less on the Interstates than does the federal government. States raise highway funds to match federal funds and to pay for other state highway projects and programs. The federal and state governments have invested heavily in Interstate highways. Because 97.4 percent of the system’s length in 2000 was complete before 1992, much of the subsequent investment was to preserve and maintain the existing system. When states added to the system’s size, they did so mainly in urban areas. From 1992 through 2000, the type of Interstate pavement and bridge construction projects also shifted from new construction to primarily maintenance. Outlays, that is, expenditures of federal, state, and other funds for projects on Interstate highways have generally increased since 1992. State spending of federal, state, and local funds for Interstates grew from $13.0 billion in 1992 to $16.2 billion in 2000. States reported total capital outlays for Interstates of $105 billion, or an average of $11.7 billion per year in 2001 dollars from 1992 through 2000. (See fig. 6.) Besides capital outlays, states also had routine Interstate maintenance outlays that averaged $1.6 billion per year. These outlays, which generally consist of nonfederal funds, were for routine tasks like sealing cracks and patching potholes, which help keep the pavement in good condition, but did not cover capital improvements like resurfacing, rehabilitation, or reconstruction. From 1992 through 2000, states allocated more of their Interstate investments of federal, state, and other funds to urban highways (68.4 percent of outlays) than to rural highways (31.6 percent of outlays). Furthermore, states have invested higher levels of state or local funds in urban projects than in rural projects. Specifically, federal Interstate obligation data for projects show that, from 1992 through 2000, rural Interstate projects averaged 11.2 percent in state or local funding, while urban projects averaged 15.1 percent in state or local funding. (See fig. 7.) States spent available funds for different types of projects on their Interstate Systems, including pavement, bridge, and other related items (including safety, traffic operations, and environmentally related projects). FHWA reported obligations of $48.5 billion for Interstate highway projects from 1992 through 2000. Of this amount, 66.2 percent, or $32.1 billion, was for pavement projects, 19.7 percent, or $9.6 billion, was for bridge projects, and the rest, $6.8 billion, was for other related items. (See fig. 8.) Accounting for the largest area of expenditures, Interstate pavement projects since 1992 were clearly focused on existing roadways. Among pavement project miles, 98.6 percent were to improve existing highways; only 1.4 percent for new construction. (See fig. 9.) Costs for improving existing highways were $29.0 billion, or 90.2 percent of total pavement costs. Only 424 miles, or 1.4 percent of Interstate projects’ length, were for new construction. (See fig. 10.) Costs for new construction were $3.1 billion, or 9.8 percent of total pavement costs. Interstate pavement construction projects from 1990 through 2000 shifted toward maintaining the existing system. Based on FHWA obligation data, new pavement construction project miles declined during the period, while reconstruction project miles tended to decline during the period and pavement maintenance project miles—restoration and rehabilitation, and resurfacing—increased. In addition, Interstate bridge projects were more likely for preservation or replacement than for new construction. Among the 11,530 bridge projects reported, 10,363, or 89.9 percent, were replacement or rehabilitation projects. The Interstate’s physical conditions (pavement and bridge) and safety are in good overall shape; however, congestion has grown. Pavement conditions improved from 1992 to 2000, and officials from 39 states now regard their pavement as good or excellent. Officials from a majority of state highway departments predict pavement will still be in good condition 10 years from now. However, officials from 23 states predict that, in 10 years, they will be falling behind in dealing with the condition of their Interstate pavement. Bridge conditions parallel pavement conditions: since 1992, bridge conditions have generally improved, and officials from a majority of states report bridge conditions are currently good or excellent, but officials from 19 states predict the condition of their bridges will worsen 10 years from now. Safety on the Interstate System has remained relatively stable. Interstate fatality rates declined from 1990 to 1992 and remained fairly stable after 1992. A majority of state officials rated the safety of travel on their Interstates as good or excellent today, and 41 predicted it will remain so 10 years from now. Moreover, DOT data showed that pavement, bridge, and safety conditions are better on Interstates than on other roads. But unlike pavement, bridge, and safety factors, Interstate congestion has gotten worse. One measure showed that rush hour travel time on urban Interstates increased 12 percent from 1990 through 2000. State officials in nearly half of the states reported that urban congestion is already high, and officials from 41 states predicted it will be high 10 years from now. State officials reported high rural congestion in only 1 state now, but expected it in 18 states within 10 years. Generally, Interstate pavement conditions have improved since 1990. According to FHWA data, 8.6 percent of Interstate pavement, or 3,897 miles, was in poor condition in 1990. By 2000, the share of poor Interstate miles had dropped to 3.4 percent, or 1,560 miles. In addition, pavement data for 1990 through 2000 show that urban Interstates have a higher percentage of poor mileage than rural Interstates, but both have improved since 1990 (see fig. 11). The improvement pattern was not continuous partly because FHWA asked the states to adopt a new condition measure. States had historically reported pavement condition using a subjective rating scale. By 1992, states were also reporting pavement data with a more objective statistic called the International Roughness Index. In 1993, FHWA adopted the roughness index as a required statistic for reporting pavement conditions on Interstates. States needed new measuring devices to adopt the International Roughness Index. When these devices were later upgraded, some states such as North Dakota, noticed an improvement in their pavement condition statistics. Two factors may have contributed to the long-term improvement in Interstate pavement. First, the federal government has increased its commitment to pavement quality, along with highway funding in general. FHWA has supported quality pavement management by promoting better planning and techniques for building smoother, longer-lasting roads. In addition, state highway programs have received increased federal funding since TEA-21 “guaranteed” certain overall funding levels based on Highway Trust Fund revenue. (See fig. 6 for increases in Interstate capital outlays during this period.) Second, state transportation departments have increased their commitment to Interstate pavement quality. This commitment may be ongoing, as in Florida, which adopted a statutory requirement in 1984 requiring goals for the quality of the pavement on its state highways. Or the commitment may come in response to customer feedback, as when Pennsylvania initiated a pavement upgrade program in response to truckers’ surveys criticizing conditions on the state’s roads. Of 51 respondents, 39 states reported that their Interstate pavement is currently in good or excellent condition; 9 said that their pavement is in fair condition; 3 reported poor Interstate pavement conditions; and none reported very poor conditions. (See fig. 12.) In addition, state pavement data submitted to FHWA for 2000 showed that for the nation as a whole, 63.5 percent of pavement was in good or very good condition, 18.2 percent was in fair condition, and 18.3 percent was in mediocre or poor condition. Half of the states reported that less than 2.0 percent of their pavement was in poor condition. FHWA’s pavement categories describe a pavement’s need for upcoming improvement as interpreted from a roughness index. Rural Interstate pavement, which gets less heavy traffic, is in better condition than urban Interstate pavement, according to data that the states supply to FHWA. According to an FHWA report on pavement conditions in 2000, only 14.4 percent of rural mileage is in poor or mediocre condition, compared with 28.2 percent of urban mileage. While the overall condition of Interstate pavement is generally good, it is much worse in certain states than our aggregate survey responses or nationwide pavement condition statistics suggest. For example, according to FHWA data, while 18.3 percent of the nation’s Interstate pavement is in mediocre or poor condition, 10 states have at least one-third of their pavement in mediocre or poor condition. Four of these states have more than 12.0 percent of their pavement in poor condition, compared with a nationwide rate of 3.4 percent for pavement in the poor condition category. Missouri, one of our case study states, has 4.1 percent of its Interstate pavement in the poor category, fairly close to the nationwide level. However, 40.1 percent of its Interstate pavement is in mediocre condition. According to a draft long-range transportation plan, many of Missouri’s Interstates need total reconstruction. State officials said that they plan to focus on I-70 between St. Louis and Kansas City, one of the oldest segments on the Interstate System, where, by state criteria, one-third to one-half of the pavement is poor or very poor. Compared with “other major arterials,” Interstates are in better condition in both rural and urban areas. According to Interstate standards, in urban areas, 6.5 percent of Interstates are in poor condition, compared with 27.0 percent of other “urban major arterials.” In rural areas, 2.1 percent of Interstates are in poor condition, compared with 4.0 percent of “other major arterials.” (See fig. 13.) FHWA has no requirements or standards for states to keep their Interstate highways in a particular condition. However, FHWA’s Fiscal Year 2002 Performance Plan included a pavement condition goal for the NHS, which includes the Interstate Highway System. FHWA originally determined that, by 2008, 93 percent of NHS pavement should have acceptable ride quality— meaning an International Roughness Index of 170 inches per mile or less. As a whole, the NHS had met this goal as of 2000, and the Interstate portion of the NHS met this goal by 1996. Since the 2008 goal had already been met, FHWA revised its performance goal. The current goal emphasizes that highly traveled roads should be in good condition and requires that, in 2002, 92 percent of vehicle miles on the NHS will be traveled on pavement that meets the acceptable ride standard. We did not find agreement on whether Interstate pavement conditions will be as good in a decade as they are now. A majority of state officials responding to our survey predict that Interstate pavement will still be in excellent or good condition 10 years from now. However, 21 respondents predict that their pavement will be in fair or worse condition. Compared with their assessments of current conditions, our respondents’ assessments of future conditions predict less pavement in good or excellent condition and more pavement in fair, poor, or very poor condition. Officials from 23 states predict that, in 10 years, they will be falling behind in dealing with the condition of their Interstate pavement. In addition, officials from 44 states predict that the portion of their transportation spending devoted to improving Interstate pavement conditions will increase (27 states) or stay the same (17 states). (See fig. 14.) DOT recently predicted that, given expected future investment levels, states could improve Interstate pavement conditions over a 10-year planning period. However, DOT’s primary funding projection could be higher than states assumed in responding to our survey. DOT projected that states would increase their Interstate funding levels from 2.8 to 3.0 percent annually in constant dollar terms from 2003 to 2007, consistent with historic trends. State officials might not assume such funding increases, according to a FHWA official. Thus, the funding level in DOT’s analysis might be higher than state officials expect, which could account for DOT’s prediction of better future pavement conditions. The number of deficient Interstate bridges has declined over the last 8 years. Specifically, the number of structurally deficient bridges declined by over 22 percent from 1992 through 2000. In addition, FHWA information also shows that the bridge deck area associated with structurally deficient Interstate bridges decreased by over 27 percent during the same period. Structurally deficient bridges can have restrictions on the weight of vehicles using them or may need to be closed and repaired before they can be used again. In addition, the number of functionally obsolete bridges declined by more than 10 percent over the same period. However, the deck area associated with functionally obsolete bridges increased 9 percent over this period. Functionally obsolete bridges are not up to design standards and generally face less serious problems than structurally deficient bridges—for example, shoulders that are not as wide as the roadway leading to the bridge. Figure 15 shows the decreasing trend in number of deficient bridges. Overall, state officials responding to our survey reported that their bridges are currently in good condition. Of the states responding to our survey, 31 said that the overall condition of their Interstate bridges is good or excellent; another 19 said it is fair. As of April 2001, 5 percent of the nation’s Interstate bridges were structurally deficient. In addition, another 16 percent were functionally obsolete. Interstate bridges are generally in better condition than those on other classes of roads. According to 1998 FHWA data, about 27 percent of urban Interstate bridges were deficient, compared with a range from over 27 percent for “urban other freeways and expressways” to over 38 percent for both “urban minor arterials” and “urban collectors.” In addition, 16 percent of rural Interstate bridges were deficient, compared with a range from 17 percent for “rural other principal arterials” to over 36 percent for “rural local roads.” Some state officials said that they are optimistic about future bridge conditions—24 expect conditions 10 years from now to be good or excellent. However, others are aware of problems bridges could face in the future. Nineteen state respondents believed that their state would fall behind in maintaining the condition of their bridges over the next 10 years, given the expected level of funding. However, they were not as concerned about falling behind on their Interstate bridges, as they were about the problems they would face with congestion and pavement condition. (See fig. 21.) In addition, officials from 32 states expect to increase the portion of their budget spent on Interstate bridges. The fatality rate on the Interstate System has been relatively steady, after falling early in the 1990s. The number of fatalities on Interstate highways has increased over the past decade, but so has the level of traffic, as indicated by the number of vehicle miles traveled (VMT). (See fig. 16.) Relatively speaking, Interstate highways are the safest of all highway classifications. We recently reported that among urban road types, “other principal arterial” roads had the highest 1999 fatality rate at 1.27— compared with 0.61, the lowest fatality rate, on urban Interstate roads. Similarly, we reported that among the rural road types, “rural local roads” had the highest 1999 fatality rate at 3.79—compared with 1.24, the lowest fatality rate, on rural Interstate roads. In addition, 45 states we surveyed said that the current level of safety on their Interstates was good or excellent. Several factors, including unique design characteristics, may contribute to the Interstate System’s higher level of safety. According to a 1999 FHWA report, most of the Interstate mileage in the country met geometric design criteria that support safe transportation in 1997. These criteria refer to the physical layout or alignment of a roadway. FHWA and states recognize guidelines established by the American Association of State Highway and Transportation Officials (AASHTO) as the appropriate design standards for many of their roads. The Interstate System meets these guidelines to a great extent—over 99 percent of urban Interstate mileage and about 97 percent of rural Interstate mileage. Almost all of the rural Interstate mileage not meeting the guidelines is in rural Alaska; about 50 percent of the urban Interstate mileage not meeting the guidelines is in Puerto Rico. Other design characteristics are also important to safety: According to FHWA, the vast majority of Interstate mileage has full access control—which FHWA policy classifies as critical to maintaining Interstate safety and mobility. Research shows that highways without access control have higher crash rates than those with access control. According to FHWA, the vast majority of Interstate mileage also consists of divided highways with at least four lanes. AASHTO’s guidance reports that a study on the effect of the Interstate Highway System on crashes found a lower crash rate on divided highways than on undivided highways. The uniformity of Interstate highway design plays a part in safety by reducing the number of decisions drivers make and thus minimizing the number of crashes related to driver error. FHWA also believes that other factors, including increased seat belt use and reduced alcohol-impaired driving, have contributed to lowering the fatality rate and the number of fatalities on the nation’s highways— including Interstate highways. State officials responding to our survey expect the safety of Interstate travel in their states to remain relatively safe. Among 51 responses, 41 said the safety of Interstate travel in 10 years will be good or excellent, 9 said travel safety would be fair, and 1 said safety would be poor. A majority of officials—29—said the portion of state transportation spending for improving safety in their states would stay about the same over the next 10 years, though 19 predicted some increase or a moderate increase. As congestion on the country’s roadways has increased, so has congestion on the Interstate System. Whether measured in terms of traffic density or travel time, congestion has increased over the past decade. Furthermore, Interstate highways are generally more congested than other freeways and other principal arterials. While there is no single indicator for congestion, we looked at FHWA’s “daily vehicle miles traveled per lane mile” to measure traffic density. As figures 17 and 18 show, the overall density of traffic on all major U.S. roads has been increasing over the past decade and traffic density is higher on urban highways than on rural ones. In addition, the traffic density on urban Interstate highways is higher than on other classes of urban road. (See fig. 17.) Although the density of traffic on urban Interstate highways is higher than on rural Interstates, traffic on rural Interstate highways is increasing at a faster rate than on any other classes of road. From 1990 through 2000, the daily vehicle lane miles traveled on rural Interstates increased at an average annual rate of 3.3 percent. By comparison, the daily vehicle lane miles traveled on rural principal arterials increased at an annual rate of 1.9 percent. (See fig. 18.) In addition, daily vehicle miles traveled on urban Interstates increased at an annual average rate of 1.7 percent, and the rate increased by 1.3 percent on other urban freeways and expressways. While daily vehicle lane miles traveled measures traffic density, it does not indicate the effect of congestion on drivers, especially the amount of time it takes them to reach their destinations. The Texas Transportation Institute has developed measures that address a central concern of urban drivers— how travel time is affected by congestion. One measure—the travel time index—indicates how much more time it takes to travel during a peak period than at other times of day. The travel time index indicates that urban Interstate congestion has increased from 1990 through 2000, and congestion levels are higher on the urban Interstate System than on any other class of roads, including urban freeways and expressways and urban principal arterials. (See fig. 19.) During the past decade, the travel time index increased by about 12 percent. This statistic provides information about drivers’ experiences as well as the level of congestion on the road because it accounts for delays due both to the traffic demand on the road and to roadway incidents, like accidents. For example, a travel time index of 1.63 means that a trip that takes 30 minutes in an off-peak (noncongested) period would, on average, take 63 percent longer, or almost 19 extra minutes in the peak period—in other words, the trip would take an average of about 49 minutes rather than 30 minutes when the road is congested. In addition, the Texas Transportation Institute data show that delay from incidents is greater than recurring delay from traffic. Specifically, their Mobility Report 2001 states that delay from incidents accounts for 54 percent of total delay. Many factors can contribute to congestion. As figure 20 shows, increases in overall population and the number of licensed drivers are factors that could each cause more cars to be on the road during peak hours. The Census Bureau reports that, from 1990 to 2000, the population increased by about 13 percent nationwide. In addition, according to FHWA, the number of licensed drivers increased by 14 percent during the past decade. These, along with other factors, resulted in a 39 percent increase in the number of miles traveled in the United States in the past decade. Freight movement by truck also increased by 40 percent over the first 8 years of the decade. However, Interstate capacity in terms of lane miles increased by only 6 percent over the past decade. Finally, expansion of metropolitan areas and the choices people make about where they live and work also contribute to congestion. Officials from 24 states rated the present level of congestion on their urban Interstates as “high” or “very high,” and officials from 21 states rated their urban Interstate congestion as “average.” By contrast, no officials rated rural congestion as “very high,” and just one official rated the level of congestion on rural Interstates as “high”; officials from 27 states rated congestion on their rural Interstates as “average.” In response to our survey, nearly all states expressed concern about future congestion on their urban Interstates. For example, 42 states predicted that, 10 years from now, they would be falling behind in terms of alleviating urban congestion and 41 states expected to rate urban congestion in the next 10 years as high or very high. (See app. II.) State respondents generally do not expect that their efforts to alleviate congestion will be entirely successful. Although 34 states indicated that they expect to spend a greater portion of their budget on urban congestion over the next 10 years, 42 states believe they will be falling behind in dealing with urban congestion. In addition, in its 1999 Condition and Performance report, FHWA predicted that congestion would worsen—that is, average travel time costs would continue rising—if investment and allocations stay at the current expected levels. In its reauthorization of surface transportation programs, Congress could decide to select methods for investing federal resources in the Interstates and other highway programs to help address local congestion problems in urban areas. To assist in making these decisions, we asked states about policies and tools that can be used in alleviating congestion. (See app. IV for the states’ responses.) Although states are particularly concerned about urban congestion levels, they also think that rural congestion will increase, especially on specific routes. Officials from 18 states expect to rate rural congestion as “high” or “very high” in the next 10 years. For example, rural congestion is increasing on the I-70 corridor—a 140-mile-long stretch through the Rocky Mountains of Colorado. This section serves in moving skiers and truckers through the mountains. However, traffic congestion has become an increasing problem along this corridor, in part due to population growth in the surrounding areas—and will continue to worsen over the years. States expect certain factors, especially the levels of truck and car traffic, the age of the Interstates’ pavement and bridges, and funding constraints to negatively affect the conditions of their Interstates over the next 10 years. FHWA data also indicate that traffic, especially the volume of truck traffic, will increase. In addition, many states believe they will be “falling behind” in satisfying the users of their systems, especially in terms of congestion. (See fig. 21.) Transportation officials have also indicated that large-dollar projects may negatively affect states’ financial ability to maintain their systems. States responding to our survey indicated that they plan to spend larger portions of their budgets addressing these Interstate pressures. However, identifying the states’ cost to maintain and improve their systems is difficult. States’ STIPs, required to include only projects that can be built with estimated revenues, show how states plan to use the funding they estimate will be available, rather than the funding they estimate will be needed for their Interstates. Some states have developed plans that provide some insight into what it will cost to maintain conditions or reach specific goals. These estimates indicate that states perceive Interstate needs as larger than estimated funding. According to our survey, states expect truck traffic to have a negative effect on the most elements of Interstate conditions including physical conditions (pavement and bridges), safety, and rural congestion. (See table 1.) For example, all 52 states expect truck traffic to increase over the next 10 years, and 49 states said that they expect this to negatively affect the condition of their pavement. Current estimates used by FHWA also show freight movement by truck increasing by 28 percent from the end of 2001 through the end of 2010. Finally, an alliance of primarily southern and southeastern states released a 2001 study that estimates an annual 6.9 percent increase in Latin American truck traffic in the United States (resulting in almost a doubling in 10 years). Ninety-six percent of this truck traffic will be on Interstates. State officials’ concerns about increases in truck traffic may reflect, in part, the estimated highway costs of damage to the pavement or bridge of each additional truck-mile driven compared with the cost of a car. A recent FHWA study explains that while car drivers pay about the same share of user taxes as their share of highway costs, heavy truck operators commonly pay less than their share of highway costs. Specifically, FHWA estimated that an additional mile of Interstate car travel cost of 0.1 cent in terms of pavement damage, while an additional mile of Interstate truck travel had a pavement damage cost as high as 12.7 cents on rural Interstates and 40.9 cents on urban Interstates. In 1994, we recommended that FHWA conduct this highway cost-allocation study. In addition to increases in truck traffic, estimates that FHWA uses show that passenger traffic will increase by 17 percent from the end of 2001 through the end of 2010—an increase from 2.7 trillion vehicle miles traveled to 3.1 trillion. States are also concerned about increases in traffic volume. Of the 52 states we surveyed, 51 predict that overall traffic volumes will increase over the next 10 years. Fifty-one of the states expect this increase in traffic volume to negatively affect urban congestion, and 41 of 51 respondents believe that the changes in traffic volume will negatively affect rural congestion. Another factor negatively affecting the condition of Interstate pavement and bridges is the age of the infrastructure. For example, half of the Interstate bridges are currently over 33 years old. Figure 22 shows when all Interstate bridges were built. Officials from one state we visited explained that many of their state’s Interstate bridges were built about 40 years ago and are reaching the end of their estimated 50-year design life. In addition, 45 states believe age may jeopardize their bridge conditions, while 38 states expect age to negatively affect their pavement conditions 10 years from now. Transportation officials are concerned that some states may face an increasing number of large-dollar projects such as work on bridges or interchanges that may constrain spending for those states’ other projects for a number of years. For example, Missouri is looking at reconstructing the 200-mile I-70 corridor at a cost of $2.5 billion to $3.0 billion. In addition, the Woodrow Wilson Bridge, which moves north-south traffic on I-95 around Washington, D.C., is expected to cost over $2 billion and is being funded by two states and FHWA. According to a Maryland official, over the 6-year project, funding for the bridge accounts for 45 percent of expenditures on major projects in the state’s capital budget. In addition, 40 states are facing budget shortfalls for 2002. Furthermore, the amount of funds available for federal highway programs may decrease for fiscal year 2003, depending on congressional action. These potential reductions in federal and state funds could reduce the funds available for maintaining the Interstates and increase states’ estimated funding shortfalls. It is difficult to identify state needs on the Interstate System and to determine what level of funding is needed to meet these needs. When surveyed, most states indicated that they expect to spend the same or increasing portions of their transportation budgets to maintain Interstate conditions. However, when states provided information on their planned expenditures, the amounts did not show a consistent upward trend, rather they varied considerably from year to year. (See table 1 in app. III.) State and FHWA officials explained that one common reason for these increases and decreases is that work on Interstates is not done in a vacuum; that is, Interstate projects must be weighed against projects on other classes of roads, such as expressways or “principal arterials.” For example, North Dakota officials explained that they are completing projects, which are focused on improving the condition of their Interstate highways. They expect to shift their attention and funding toward projects on other classes of roads. In addition, states’ federally required plans do not usually provide information on all needs and related costs. States’ short-term STIPs do not identify funds needed to maintain Interstate conditions because they include lists of proposed projects that can be built with estimated revenues. Therefore, as state and federal officials explain, STIPs reflect affordability rather than identifying projects that are needed and would be constructed if additional funding were available. In addition to STIPs, states are required to develop long-term (20-year) plans. However, these plans may not contain specific projects and cost estimates, and thus do not provide information on states’ needs and related costs. Nevertheless, some states have developed additional transportation plans that identify long-term funding gaps for various parts of their highway networks, including the Interstates. For example, North Dakota is developing a needs estimate for its state roads (excluding urban Interstates). The state defined its need by using criteria for pavement, bridge, design, and safety conditions. State officials estimated the funds needed to bring the roads (except urban Interstates) to the desired physical condition and level of performance as nearly a billion dollars more than available. According to state officials, eliminating the backlog will require either an increase in revenue or a decrease in service. In addition, in 2001, Florida officials estimated that to meet capacity needs on its Intrastate System (including Interstates), it would need $20 billion more through 2010 than the $11 billion it expects to have. Missouri’s draft 2000 long-term plan also indicates that the state’s needs outweigh the available funds. Interstate highways continue to play a vital role in moving people and freight in this country. Over the past few decades, however, they have taken on an important and expanded role in facilitating travel within urban areas. They have also become central to moving freight and, as a result, to economic growth. These roles will continue to be important; however, they have consequences that will challenge the federal government and state and local governments in assuring that Interstate highways continue to provide efficient travel and remain in relatively good condition. In particular, the challenges for Interstate highways include finding effective methods of easing traffic congestion, particularly in providing for efficient freight movement given increases in both passenger and freight traffic; and responding to the effect of traffic on roads and bridges given the continued aging of these structures. We provided a draft of this report to DOT and DOD for their review and comment. DOT officials, including the Team Leader for Highway Needs and Investment Analysis within FHWA, provided oral comments. They generally agreed with the observations in the report, and they also provided technical comments, which we incorporated in the report as appropriate. DOD officials, including the Chief, Office of Special Assistant for Transportation Engineering, Military Traffic Management Command, provided technical comments, which we incorporated as appropriate. We conducted our review from March 2001 through April 2002 in accordance with generally accepted government auditing standards. As arranged with your office, unless you publicly announce its contents earlier, we plan no further distribution of this report until 7 days after the date of this letter. At that time, we will send copies of this report to cognizant congressional committees; the Secretary of Transportation; and the Administrator, Federal Highway Administration. If you or your staff have any questions about this report, please contact me at (202) 512-2834. Appendix V lists the key contacts and contributors to this report. With the upcoming reauthorization of the surface transportation programs, the House Committee on Transportation and Infrastructure asked us to report on Interstate highways and bridges. Accordingly, this report examines the condition of the Interstate System, including, (1) how the role of the Interstate System has changed over time; (2) the roles of the federal and state governments in managing and funding the Interstate System; (3) the financial resources that states and the federal government have devoted to the system; (4) how physical conditions, safety, and congestion of the Interstate System have changed and how they compare to other classes of roads; and (5) the factors that could affect future Interstate conditions and the cost of addressing these factors. To determine how the role of the Interstate System has changed over time, we reviewed historical documents. We also conducted a nationwide mail survey of state transportation agencies in all 50 states, the District of Columbia, and Puerto Rico. Our survey focused on state officials’ views on the changing role of Interstate highways in their states’ transportation systems; the usefulness of various approaches for addressing operations and maintenance of their Interstate highways and bridges; their views on the Interstate System in 10 years; and their perceptions of the current condition of their Interstate System’s infrastructure, safety, and congestion. We received survey responses from all 52 governments—most states responded to most of the questions. A summary of responses to the survey appears in appendix II of this report. To develop our mail survey, we discussed potential survey topics with state officials in two states to determine how to design our survey questionnaire. Then, we conducted pretests of our questionnaire with transportation officials in four states. We selected states for our survey development phase to provide perspectives from a variety of geographic areas and from states with various types of weather, population patterns, and other factors that affect Interstate planning. Each of the four pretests consisted of a visit with state officials by our staff to ensure that (1) questions were readable and clear, (2) terms used were clear, (3) the survey did not place undue burden on state governments that would result in a lack of cooperation, and (4) the survey was independent and unbiased in its point of view. Appropriate changes were incorporated into the final survey based on our pretesting. In addition to our pretesting, we discussed our questionnaire with an official at FHWA headquarters and representatives of the AASHTO in Washington, D.C. We incorporated comments from these discussions, as appropriate. To determine which officials should receive our survey, we used AASHTO’s Reference Book to identify the appropriate state officials. We verified our selection by contacting FHWA division officials in most of the 52 locations. During the return period, an unprecedented terrorist incident occurred on September 11, 2001. Although it is possible that the responses completed after this date may have differed from those received beforehand, our analysis of the question of the role of the Interstates in moving military personnel and equipment shows that answers did not differ for these two time periods. We received the last survey included in our analysis on November 21, 2001. To address our second objective, we reviewed historical Federal-Aid Highway Program data obtained from FHWA, which discussed why the Interstate System was developed and the roles Congress, FHWA, DOD, and states played and how they have evolved into the current roles. We also interviewed FHWA and DOD staff about their roles and identified current federal requirements related to the Interstates. Finally, we examined federal apportionments to the states for Interstates as well as other activities. For our third objective, we analyzed FHWA’s obligation of funds for Interstate-related projects. We also reviewed outlays from all levels of government for Interstate-related projects, as reported by states on an annual basis. For the fourth objective, we used the responses to our survey described previously. To compare conditions of Interstate highways to other classes of roads as well as obtain trend information on Interstate highway conditions, we reviewed DOT’s published data on actual highway conditions and its forecasts of potential future conditions. To learn how officials assess Interstate highway conditions in their states, we interviewed officials in Arizona, Florida, Missouri, North Dakota, and Pennsylvania. We selected these states to obtain perspectives from a variety of regions with various types of weather, population differences, and other factors that affect Interstate planning. In addition, to determine the current condition of the Interstate System in terms of congestion, we relied on a number of measures reported by FHWA. We requested FHWA to obtain Texas Transportation Institute analysis of congestion levels on Interstate highways in comparison with other classes of roads. We also reviewed DOT’s Bureau of Transportation Statistics and U.S. Census Bureau data on factors related to congestion trends. Furthermore, to assess safety, we reviewed data from the National Highway Traffic Safety Administration’s Fatality Analysis Reporting System, and FHWA data on trends in fatality rates and number of fatalities. To address the last objective, we analyzed state survey responses and discussed the factors with state and FHWA officials during our site visits, as necessary. We focused on factors such as demographic changes or changes in traffic, but we did not focus on the influence of federal funding through the existing Federal-Aid Highway Program on state’s decisions about their investment in Interstate roads and bridges. To examine states’ plans for Interstate investment, we asked states to provide information on their planned costs for their Interstate highways in our survey. We reviewed states’ written plans for investment in Interstate highways and other roads. Again, we also visited the five states mentioned earlier to obtain more detailed information on their planning. Additionally, we interviewed FHWA division officials to obtain a general overview of FHWA’s approach to assisting states with their Interstate System plans. We conducted our review from March 2001 through April 2002 in accordance with generally accepted government auditing standards. States must meet specific planning requirements set forth by federal law. In addition, state transportation agencies may face state-level requirements. Within these requirements, states develop plans to allocate available funds throughout their transportation systems. Federal law requires each state to develop at least two planning documents—a 20-year Statewide Transportation Plan and a short-term Statewide Transportation Improvement Program (STIP) that covers at least 3 years. The STIP should include a list of proposed projects that is financially constrained—that is, projects that can be built with estimated revenues. States must submit their proposed STIPs to FHWA and the Federal Transit Administration for joint approval at least every 2 years; however, the STIPs may be amended at any time, subject to federal approval. Some states also have policies or laws that direct the use of their funds. These directives are taken into consideration when planning projects. For example, Florida officials are concerned about the safety and preservation of the current system. First, the state addresses safety in all their transportation projects. Next, it is the state’s policy to preserve the existing system before spending anything on new construction. In addition, Florida law requires that at least 50 percent of the amount of new funds available for capacity construction must go towards the state’s Intrastate system. Also, in Arizona, according to a statewide agreement, 50 percent of the funding available to the Arizona Department of Transportation must be spent on state highway projects within the Phoenix and Tucson metropolitan areas, and the remaining 50 percent must be spent on state highway projects outside these two metropolitan areas. To develop these planning documents and maintain their Interstate highways, states use a variety of planning approaches. For example, Florida has a complex system relying on policies, measurable objectives, and performance monitoring to make its investment decisions. Florida officials develop a 20-year long-range policy plan. Based on this 20-year plan, they develop a 10-year program and resources plan containing program funding levels given estimated revenues. Finally, the officials develop and update annually a 5-year list of projects. To help select specific projects that meet their goals, Florida officials use decision support software to consider a multitude of data, including pavement condition surveys, biennial bridge inspections, routine maintenance, safety data, and analyses of congestion levels. Arizona is revising its long-term planning process. In the meantime, Arizona is using an interim process to develop its 5-year construction program. To identify states’ plans to meet Interstate needs over the next few years, we asked states to provide information on the level of funding directed toward the Interstates. Table 2 shows the amount states plan to spend in 2001 and the increases and decreases compared with 2001 throughout the 5 subsequent years. The states in bold indicate states included in our site visits. States’ views differ on effectiveness of congestion relief tools. We surveyed the states about the tools they were using to relieve congestion and the tools’ usefulness. Although we identified below some of the tools mentioned on our survey, based on our case study states, we found that different tools may be more effective in one state than in another. For example, adding lanes may be a useful tool to deal with congestion for states with relatively low population density; however, this tool may not be useful for states with relatively high population densities—particularly in their urban areas, where the ability of adding lanes is limited since many urban areas have the maximum number of lanes that will fit into available space. States reported using a variety of tools and varied in their assessment of the tools’ usefulness. For example: Increasing capacity through the addition of lanes. Forty-four states indicated that adding lanes to increase capacity is very useful or moderately useful. Redesigning problematic highway sections. Three-fourths of the 52 states found redesigning highway sections to address traffic bottlenecks to be very useful or moderately useful. Using traffic incident management tools. About two-thirds of the state departments of transportation stated that traffic incident management tools (e.g., protocols for handling accidents) were very useful or moderately useful. Using technology for handling high-volume traffic—such as variable message signs, ramp metering, and electronic tolls—42 states found these to be useful. Providing alternative transportation modes to reduce Interstate traffic (e.g., buses, rail, and ferries)—12 states found these to be very useful or moderately useful. Providing incentives to drivers to reduce congestion. While 30 states used these techniques—for example, reserving lanes for high-occupancy vehicle and varying tolls by time of day—only 15 states believed them to be very useful or moderately useful. In addition to those named above, Carolyn Boyce, Richard Calhoon, Jennifer Clayborne, Catherine Colwell, Fran Featherston, Timothy J. Guinane, and Josephine Perez made key contributions to this report. 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Summary: Federal spending on Interstate highways has contributed to changes in residential and business land-use patterns. In 1991, GAO raised concerns about the condition of Interstate highways and rising levels of congestion. The original purposes for the Interstate system were to provide for efficient long-distance travel, support defense, and connect metropolitan and industrial areas. Today, the most important role that the Interstates perform, other than supporting safe travel, is moving freight traffic across their states. The federal government provides funding for, and oversight of, the Interstate system while the states do most of the maintaining and planning for the future of the system. Combined federal and state spending on the Interstate System increased from $13.0 billion in 1992 to 16.2 billion in 2000. States are required to pay ten percent of the cost of an Interstate project; however, GAO found that the average nonfederal share of urban Interstate projects was 15 percent and 11 percent for rural projects. Interstate highways are in better physical condition and are safer than other classes of roads, although they are generally more congested. The states expect that increased traffic, the aging of the infrastructure, and funding constraints will affect their ability to maintain physical and safety conditions of the Interstate Systems and to alleviate congestion, but the costs to address the factors pressuring their Interstates were difficult to determine.