In the first wave, all six planes (carrying one bomb each) hit their target, but one of the aircraft crashed near Frederiksberg Girls School. Because of this crash, four of the planes in the two following waves assumed the school was the military target and aimed their bombs at the school, leading to the death of 123 civilians (of which 87 were schoolchildren). However, 18 of the 26 political prisoners in the Shell Building managed to escape while the Gestapo archives were completely destroyed. On 8 May 1945 Copenhagen was officially liberated by British troops commanded by Field Marshal Bernard Montgomery who supervised the surrender of 30,000 Germans situated around the capital. Shortly after the end of the war, an innovative urban development project known as the Finger Plan was introduced in 1947, encouraging the creation of new housing and businesses interspersed with large green areas along five "fingers" stretching out from the city centre along the S-train routes. With the expansion of the welfare state and women entering the work force, schools, nurseries, sports facilities and hospitals were established across the city. As a result of student unrest in the late 1960s, the former Bådsmandsstræde Barracks in Christianshavn was occupied, leading to the establishment of Freetown Christiania in September 1971. Motor traffic in the city grew significantly and in 1972 the trams were replaced by buses. From the 1960s, on the initiative of the young architect Jan Gehl, pedestrian streets and cycle tracks were created in the city centre. Activity in the port of Copenhagen declined with the closure of the Holmen Naval Base. Copenhagen Airport underwent considerable expansion, becoming a hub for the Nordic countries. In the 1990s, large-scale housing developments were realized in the harbour area and in the west of Amager. The national library's Black Diamond building on the waterfront was completed in 1999. Since the summer of 2000, Copenhagen and the Swedish city of Malmö have been connected by the Øresund Bridge, which carries rail and road traffic. As a result, Copenhagen has become the centre of a larger metropolitan area spanning both nations. The bridge has brought about considerable changes in the public transport system and has led to the extensive redevelopment of Amager. The city's service and trade sectors have developed while a number of banking and financial institutions have been established. Educational institutions have also gained importance, especially the University of Copenhagen with its 35,000 students. Another important development for the city has been the Copenhagen Metro, the railway system which opened in 2002 with additions until 2007, transporting some 54 million passengers by 2011.