Songshan–Xindian line

Initial plans for the line originally called for another station between Zhongshan and Beimen stations (at Chien-Cheng Circle). However, the Circle was suffering from economic concerns, as well as engineering feasibility and effectiveness problems. Coupled with problems with landowners regarding joint developments and two of the entrances/exits, plans for the station were shelved on 1 May 2007.[5] The station would have been a five-level underground station with stacked, split platforms.[6]

It was originally estimated that its opening would take place in 2013.[7]

Shield tunneling was used to construct most of the tunnels on the line, except for a few locations.[8] Tunneling beneath Dacheng St. crosses existing Taiwan Railway Administration and Taiwan High Speed Rail tunnels.[8] Common utility ducts were constructed in sync with the Metro line, carrying water pipes, gas pipes, and cables.[9] Over 200 homes were demolished or relocated to make way for Metro land use.[10]

Construction of the line was divided into three civil engineering section contracts and one electrical/mechanical system-wide contract.[11] The contract for construction on the eastern end of the line (including Nanjing Sanmin and Songshan) was awarded to Da Cin Construction Co., Ltd. on 2 March 2006.[12] The 3.02 km (1.88 mi)-long section includes a crossover section, a tail-track work shaft, and three shield tunnels. Construction of the line was completed in late 2014.

In 2008, steel price increases threatened to delay construction plans due to the price doubling over the previous two years.[13] The Ministry of Economic Affairs ordered that exports of other steel products be strictly supervised to ensure a steady local supply and to keep prices down.

Taipei Workshop, a 3rd level historical monument constructed during the era of Japanese rule, was exactly where the proposed Beimen station would be located. Thus, a temporary removal project commenced on 20 October 2006 to move the structure until construction of both the Songshan Line and the Taoyuan International Airport MRT are completed.[14][15] The building moved 30 meters to the southeast, and moved back when construction is completed.[16]