Taipei, March 2 (CNA) A project that will take part of the Taiwan Railways Administration (TRA) stations in Taoyuan underground will start in April 2022 and is expected to contribute to swifter rail transit in northern Taiwan, transport officials said on Tuesday.

The two-phase project will first put the existing TRA stations of Taoyuan, Zhongli and Neili underground by 2029, following calls for upgraded facilities due to a growing number of passengers using the stations, according to the Railway Bureau.

The bureau said another five underground stations will be added to the line -- Fengming in New Taipei, as well as Zhonglu, Taoyuan Hospital, Chungyuan and Pingzhen in Taoyuan -- which are planned to begin operation in 2030.

The 17.9-kilometer line will be linked to an extended route from the existing Taoyuan Airport metro via Zhongli Station, which is expected be completed in 2028, according to the Department of Rapid Transit Systems of the Taoyuan City government.

Meanwhile, the NT$104.8 billion (US$3.77 billion) underground project will also intersect with the green line of the Taoyuan mass rapid transit system via Taoyuan Station, the department said.

Currently under construction, the green line is scheduled to start operation in 2026, the department said, adding that the entire urban planning project, which will include an additional three lines, will make it more convenient to travel to the city's three hubs -- Taoyuan, Zhongli and the Taoyuan Aerotropolis area.