At present Taiwan Railway Administration (TRA) services from Taipei to east coast cities run northeast from the capital through New Taipei City and Rueifang, before following the Pacific coast south towards Toucheng.
Under the RRB's preferred option, the new line would run inland from the Nangang district of Taipei, passing through New Taipei City before rejoining the existing line at Shuangxi. The 53km line will require the construction of two major tunnels, one of which will be 21.6km long, making it Taiwan's longest tunnel.
The RRB says it expects the NT 50bn ($US 1.65bn) project to be completed by 2026, reducing the fastest Taipei – Yilan journey times from 1h 5min to 47min.
The RRB had also considered a second more direct alignment between Pinglin in New Taipei City and Toucheng, but the 36.3km route would pass through the water table of the Feitsui reservoir, which provides drinking water to Taipei. It would also encounter six geological faults and abandoned mine workings.