and Nuclearelectrica. Fossil fuels are the country's primary source of energy, followed by hydroelectric power. Nuclear energy in Romania Due to dependency on oil and gas imports from Russia, the country has placed an increasingly heavy emphasis on nuclear energy since the 1980s. The Cernavodă Nuclear Power Plant is the only one of its kind in Romania, although there are plans to build a second one in Transylvania, possibly after 2020. For domestic heating and cooking 48% of rural and small-town households use directly burned solid fuel (almost exclusively domestically produced wood) as the main energy source. Wind power had an installed capacity of 76 MW in 2008, and 3028 MW in 2016. The country has the largest wind power potential in Southeast Europe, with Dobruja listed as the second-best place in Europe to construct wind farms. As a result, there are currently investor connection requests for over 12,000 MW. There are also plans to build a number of solar power stations, such as the Covaci Solar Park, which will be one of the largest in the world. Physical infrastructure The volume of traffic in Romania, especially goods transportation, has increased in recent years due to its strategic location in South-East Europe. In the past few decades, much of the freight traffic shifted from rail to road. A further strong increase of traffic is expected in the future. As of December 2020, 914 km of motorways are in use with a small portion of Lugoj-Deva (between Margina and Holdea)to be finished while Sibiu-Pitesti is still tendering. The railway network, which was significantly expanded during the Communist years, is the fourth largest in Europe. Bucharest is the only city in Romania which has an underground railway system, comprising both the Bucharest Metro and the light rail system managed by Regia Autonomă de Transport București. Although construction was planned to begin in 1941, due to geo-political factors, the Bucharest Metro was only opened in 1979. Now it is one of the most accessed systems of the Bucharest public transport network with an average ridership of 800,000 passengers during the workweek. In total, the network is 71 km long and has 53 stations. Sectors of the economy Gas and natural resources Romania has become a natural gas exporter. Romanian Scientist, Lazar Edeleanu, had managed, for the first time in the world, to refine oil based products with sulphur dioxide, in other words separation