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.