The northern and southern sections are connected, forming one complete line from Shanghai Railway Station - Xinzhuang. December 28, 2004 - Line runs from Gongfu Xincun - Xinzhuang after northern extension opens. December 29, 2007 - Second northern extension opens; full line runs from Fujin Road - Xinzhuang. Stations Service routes Important stations - Connects the metro with the main railway station in the city, allowing rail transport to and from other provinces. Virtual Interchange with lines 3 and 4. - This station serves a business and shopping area, and is also close to multiple tourist attractions making the station busy all day long. Interchange with lines 2 and 8. - This is a business and commercial area, also with tourist attractions such as the Xujiahui Cathedral. Interchange with lines 9 and 11. - This station is located at the sports stadium of the same name and the biggest regional and long distance bus station in the city. Interchange with line 4. - This station serves the second railway station of the city, which accommodates trains serving cities mainly to the south. Interchange with lines 3 and 15. - The southern terminus of line 1; interchange with line 5. Future expansion West extension of line 1 A extension to Humin road (North Xinzhuang Station) has been approved as part of the National Development and Reform Commission has approved the 2018-2023 construction planning of the city's Metro network. Work is expected to begin before 2023 and will take 4 years at acost of US$518. The extension will connect to the under construction Jiamin line. Headways <onlyinclude> <onlyinclude> Technology Signalling As the first line in the system, Shanghai Metro was conceived and designed during 1980s, when fixed block signalling and track circuit based train control (TBTC) was still considered a state-of-art approach to automatic train operation. The signalling system was designed by CASCO, a signalling manufacturer owned jointly by China Railway Signal & Communication Group Corporation (CRSC) and General Railway Signal (GRS), and was largely based on the system designed by GRS for the Washington Metro. Coded audio-frequency (AF) track circuits are used for both train detection and transmission of speed commands, as well as limited train-to-wayside communication (TWC) for automatic train supervision (ATS). Train operation between stations and station stop can be automatic, while doors are controlled manually by train operators. From 2013 to 2019, the system was completely renewed, with