Currently, seven Class I railroads own and maintain over 61,000 bridges and over 800 tunnels, and 40 Class II and 509 Class III railroads own and maintain over 15,000 bridges. According to FRA documents, in 2002, the U.S. railroad network contained approximately one bridge for every 1.4 miles of track. Class I railroads operate on approximately 70 percent of the total route miles in the United States and generate 90 percent of total railroad revenues. Class II and III railroads also play a critical role in the national freight railroad network, serving as feeders to Class I main lines. According to the American Short Line and Regional Railroad Association (ASLRRA), Class II and III railroads handle one out of every four carloads moved on the U.S. freight railroad system. Between 1978 and 2004, railroad traffic on Class I railroads increased dramatically while the number of railroad track miles decreased, as evidenced by an increase in the ratio of train-miles to track-miles (see fig. 1). In addition, freight volumes increased, as evidenced by a 105 percent increase in ton-miles per route-mile since 1990, from 8.63 million in 1990 to 17.70 million in 2005 (see fig. 2). These changes have focused more and heavier traffic over fewer core lines, thereby increasing both the strain on and the importance of key bridges and tunnels, such as those over the Mississippi River and underneath Baltimore. Bridges and tunnels on the freight railroad network are aging and are susceptible to a variety of conditions that may cause wear or deterioration. Railroad bridges are constructed from timber, steel, masonry or concrete, or a combination of these materials. According to an FRA bridge survey completed in 1993, more than half of the nation’s railroad bridges were built before 1920. This survey, which FRA’s Chief Structural Engineer told us is largely applicable today, found that 36 percent of railroad bridges were made of timber, 32 percent of steel, and 20 percent of masonry; the remaining 12 percent of bridges were not identified by bridge type. Increased weight and traffic can cause fatigue in timber and steel bridges. Timber bridges are also susceptible to decay from weather and insects, and steel bridges near salt water may be susceptible to high rates of corrosion. Masonry bridges are more vulnerable to the effects of time and nature than to the weight of traffic, but reinforced concrete bridges are susceptible to the effects of traffic loads. According to FRA, from 1998 through 2006 a total of 22 train accidents, involving one injury and no fatalities, were attributed to bridge structural failures. The most recent fatality resulting from a bridge structural failure occurred in 1957. Likewise, very few major railroad tunnels have been built within the last 50 years, according to FRA’s Chief Structural Engineer, although some have undergone maintenance or capacity expansion in recent years. Some tunnels are driven directly through rock; some are lined with brick or stone masonry, concrete, or timber; and many tunnels include two or more types of construction. Tunnels do not take stress from train traffic in the same way that bridges do, but they are susceptible to drainage issues, and timber-lined tunnels are particularly susceptible to fires. According to FRA, from 1982 through 2006 there were five reportable train accidents whose cause could have been related to the tunnel structure. One of these accidents resulted in two injuries, and none of the accidents resulted in a fatality. Many railroad bridges and tunnels were designed to have long useful life- spans, but were built for use by different types of trains. Until recent years, stress from locomotives and cars did not exceed the original design loads for bridges. For example, steel bridges built between 1895 and 1916 were engineered for steam locomotives that inflicted greater stress on bridges than today’s locomotives. However, because of their increased weight, freight cars are approaching the design load limits of older bridges. Railcar weight standards have increased from 263,000 pounds to 286,000 pounds, and some cars now weigh as much as 315,000 pounds; however, approximately 45 percent of Class II and III railroad lines are not equipped with track capable of handling 286,000 pound cars, according to ASLRRA. In addition, freight cars have increased in height as increased intermodal freight traffic has led to double-stacking intermodal containers on railroad cars. Some bridges and tunnels do not have the clearance needed to accommodate these double-stack intermodal trains. The majority of the freight railroad network is privately owned, and federal economic regulation of freight railroads has decreased since the federal government deregulated the railroad industry in 1980. All seven Class I railroads are privately owned, and according to ASLRRA, approximately 95 percent of Class II and III railroads are privately owned, with the rest owned by government entities. Private railroads have an incentive to maintain their infrastructure in order to maintain business operations, and most railroads privately finance their infrastructure maintenance and improvement projects. Railroads invest large amounts in fixed assets such as track, signals, bridges, and tunnels. The Association of American Railroads (AAR) estimates that in calendar year 2006 Class I railroads alone invested over $8 billion in “capital commitments,” that is, expenditures for capital projects and operating leases. Compared with other industries, railroads invest a higher percentage of revenue in their infrastructure. For example, in 2000, the average U.S. manufacturer spent 3.7 percent of revenue on capital spending, while railroads spent 17.8 percent—almost five times as much, according to an analysis of U.S. Census data prepared by the American Association of State Highway and Transportation Officials (AASHTO). As railroads take steps to increase their capacity—by increasing the size or weight of railroad cars or by adding track—some of their bridges and tunnels may require alterations. A bridge’s configuration and condition dictates weight restrictions, and most bridges and tunnels cannot accommodate the additional track, if needed, without replacement or significant reconstruction. Similarly, the dimensions of some bridges and tunnels restrict railroad car height and width. Because bridges and tunnels are the most expensive pieces of railroad infrastructure, with replacement and construction costs ranging from 11 to 550 times as much per linear foot as regular track, capacity expansion projects involving bridge and tunnel work require significant capital investment. While the freight railroad industry is projected to grow substantially with expected increases in freight traffic, the industry’s ability to fund this projected growth, including making needed capital infrastructure investments in railroad bridges and tunnels, is largely uncertain. For private companies seeking to maximize returns to stakeholders, railroad investment poses a substantial risk. A railroad contemplating an infrastructure investment must be confident that the market demand for that infrastructure will hold up for 30 to 50 years. Furthermore, while railroads own and maintain their own infrastructure, some other modes of transportation, such as the trucking and maritime barge industries, use infrastructure that is owned and maintained by the government, providing them with a competitive price advantage over railroads. We have previously reported that railroad investment is critical to freight mobility and economic growth, and investments in railroad projects can produce public benefits, such as (1) reducing highway congestion, (2) strengthening intermodal connections and the efficiency of the publicly owned transportation system, and (3) enhancing public safety and the environment. (See the list of related GAO products at the end of this report.) However, even when the public benefits of freight projects may be sufficient to warrant public funding, federal funding mechanisms may not be well tailored to freight projects. Whereas freight projects are frequently intermodal, most federal funding mechanisms are focused on one mode. In addition, freight projects generate private benefits, raising questions about whether and how to provide public support for them. Major railroads collect and maintain detailed information on the condition of their bridges and tunnels and on the extent to which these structures contribute to network congestion, but less is known about how much information Class II and III railroads collect. Freight railroads generally consider this information proprietary, citing concerns over security and liability, and they selectively share bridge and tunnel information with the government. Meanwhile, the federal government plays a limited role in collecting information on railroad bridges and tunnels because they are privately owned and maintained. In addition, FRA has no regulations or standards for railroad bridges and tunnels; and, in FRA’s view, the safety benefits that might accrue from collecting and maintaining information on their condition would not justify the expense. Various other federal agencies collect some information on railroad bridges and tunnels that pertain to their mission. While most bridges and tunnels are not the main cause of freight railroad congestion, some structures are chokepoints and do constrain capacity. Freight railroads set maintenance and investment priorities by considering bridge and tunnel information, together with comparable information on other components of their network infrastructure, and identify those repairs and improvements that will improve safety, provide the highest return on investment, and increase capacity. A bridge or tunnel is likely to cost more to repair—and much more to replace—than other components of railroad infrastructure networks, such as track or signals. As a result, railroads of all classes are more likely to invest in other components sooner and to consider extensive bridge or tunnel repair or replacement as one of their last investment options. Class I railroads, which own over 75 percent of U.S. railroad bridges and over 800 tunnels, maintain detailed information on the condition of their bridges and tunnels and generally have the resources to invest in a robust maintenance and inspection regime; however, less is known about the information Class II and III railroads collect on bridge and tunnel conditions, according to FRA’s Chief Structural Engineer. Officials from five of six Class I railroads with whom we spoke said they maintain bridge and tunnel information electronically in databases—including data on location, age, and other characteristics of the structures; inspection reports; condition information, maintenance histories, design drawings or construction documents; and other pertinent information.