The Shenzhen Metro () is the rapid transit system for the city of Shenzhen in Guangdong province, China. Extensions opened on 28 December 2022 put the network at of trackage, operating on 16 lines with 369 stations. Shenzhen Metro is the 4th longest metro system in China and 4th longest in the world as of that date despite having only opened on 28 December 2004. By 2035 the network is planned to comprise 8 express and 24 non-express lines totaling of trackage. Current system Currently the network has of route, operating on 16 lines with 369 stations. Line 1, Line 4 and Line 10 run to the border crossings between the Shenzhen Special Economic Zone and the Hong Kong Special Administrative Region at Luohu/Lo Wu and Futian Checkpoint/Lok Ma Chau, where riders can transfer to Hong Kong's MTR East Rail line for travel onwards to Hong Kong. Line 1 Line 1, formerly known as Luobao line runs westward from Luohu to Airport East. Trains operate every 2 minutes during peak hours and every 4 minutes at other times. The line is operated by SZMC (Shenzhen Metro Group). Line 1's color is green. 28 December 2004: Luohu – Window of the World 28 September 2009: Window of the World – Shenzhen University 15 June 2011: Shenzhen University – Airport East Line 2 Line 2, formerly known as Shekou line runs from Chiwan to Liantang. Line 2 is connected with Line 8 at Liantang station. The line is operated by SZMC (Shenzhen Metro Group). Line 2's color is orange, the same as Line 8. 28 December 2010: Chiwan – Window of the World 28 June 2011: Window of the World – Xinxiu 28 October 2020: Xinxiu – Liantang Line 3 Line 3, formerly known as Longgang line runs from Futian Bonded Area to Shuanlong in Longgang, in the north-east part of the city. Construction began on 26 December 2005. The line is operated by Shenzhen Metro Line 3 Operations, which has been a subsidiary of SZMC (Shenzhen Metro Group) since 11 April 2011 when an 80% stake was transferred to SZMC. Line 3's color is sky blue. 28 December 2010: Caopu – Shuanglong 28 June 2011: Yitian – Caopu 28 October 2020: Futian Bonded Area – Yitian Line 4 Line 4, formerly known as Longhua line runs northward from Futian Checkpoint to Niuhu. Trains operate every 2.5 minutes at peak hours and