Line 15 of the Beijing Subway (simplified Chinese: 北京地铁15号线; traditional Chinese: 北京地鐵15號線; pinyin: běijīng dìtiě shíwǔhào xiàn) is a rapid transit rail line in northern Beijing with one portion in operation and the remainder under construction. In all, the line is set to have a total length of 45.7 km across northern Beijing from Xiyuan in Haidian District in the west, to Hedong in Shunyi District in the east. Construction is occurring in two phases. Phase I covers the eastern half of Line 15 from Beishatan in Chaoyang District to Fengbo in Shunyi District. It will cost ¥17.6 billion. Construction on Phase I began on April 11, 2009. Section 1 of Phase I, from Wangjing West to Houshayu entered operation on December 30, 2010. Section 2 of Phase I, from Houshayu to Fengbo, entered operation on December 30, 2011. Section 3 of Phase 1 is set to follow in 2013. Phase II is expected to be completed by 2015.