The Beijing Subway opened in 1971 and is the oldest metro system in mainland China and on the mainland of East Asia. Before the system began its rapid expansion in 2002, the subway had only two lines. The existing network still cannot adequately meet the city's mass transit needs. Beijing Subway's extensive expansion plans call for of lines serving a projected 18.5 million trips every day by 2021. The most recent expansion came into effect on December 31, 2020, with the extensions of Line 16 and Fangshan line.