River and I-85 from the Connector north to I-285. This marked the true end of Freeing the Freeways as all the urban and suburban widening projects were complete and the HOV lanes initially built in the late 1980s were finally opened and operating. Railroads Georgia boasts one of the most extensive freight rail systems in the U.S., with some 5,000 miles of track that run through almost all of the state's 159 counties. The system primarily consists of two Class 1 railroads—Norfolk Southern and CSX—and 25 shortlines. 29 percent (1,433 miles) of the state's railroad system is operated by 25 independent or short-line operators. Light density lines The DOT owns nearly 540 miles of light density rail line. Approximately 90 percent of the 540 miles is leased to a shortline operator. The remaining 10 percent is leased to the Georgia Department of Natural Resources for use as a bicycle and pedestrian trail, is inactive, or is not leased. Norfolk Southern has approximately 851 miles of light density lines and CSX has another 242 miles. Georgia's light density lines carry less than 5 million gross tons of freight per year and function as local shortline service operators, primarily in rural agricultural areas. Mainlines 2,463 miles of the rail system are classified as "mainline track". Some Georgia mainlines transport more than 80 million gross tons per year, ranking them among the most heavily used in the country. Air transportation Aviation Programs Aviation Programs is tasked to assure a safe, adequate, and well-maintained system of public-use airports, to promote and encourage the use of aviation facilities, to guide airport development, to promote viable scheduled air service throughout the state, and to foster safer operating conditions at these facilities. Other responsibilities Aviation Programs is responsible for inspecting and licensing all open-to-the-public general aviation airports in the state. State law requires public-use airports to have a state airport license. Licensing occurs on a biennial basis. Aviation Programs also publishes and distributes to the airports and aviation community the Georgia Airport Directory and the Georgia Aeronautical Chart in alternating years. State Block Grant Program Georgia was designated by the FAA as the 10th participant in the State Block Grant Program beginning October 1, 2008. This mandates the department to accept and administer millions of dollars in federal funding for improvements at federally eligible general aviation airports. Aviation Programs assumes additional responsibility for project oversight, airport planning,