The Circular or ****Yellow line (code Y) is a metro line in New Taipei City, part of the New Taipei Metro, which was previously a line of the Taipei Metro. Currently the line runs between and, it is approximately 15.4 km long with 14 stations. This initial section was opened on 31 January 2020. Hitachi Rail Italy supplied 17 sets of 4-car driverless medium-capacity trains for the line. Extensions to the north and south are currently under construction.

Construction

Hitachi Rail STS supplied electromechanical equipment for the line, including driverless technology and CBTC signaling. , currently the only underground station on the line, was constructed by RSEA Engineering Corporation and employed the cut-and-cover method. Construction for the first phase officially broke ground on 11 July 2011 on a 6.3 km elevated section between Zhonghe and Banqiao. The section is estimated to cost NT$13.7 billion, with the entire first-stage 15.4 km route estimated to cost NT$54.7 billion to construct. The line includes the first elevated split platforms in the system at, , and due to the narrowness of the available station area. The initial section between and opened on 31 January 2020. On 5 May 2023, the Circular line has been transferred from the Taipei Metro to the New Taipei Metro, with the fare structure still integrated with Taipei Metro system, unlike light rail lines of New Taipei Metro.

Public art

Unlike previous public art installations on the metro, it was decided that a smaller number of art pieces would be installed within the same budget, allowing for large-scale artwork. Across the above ground section of the line, Emmanuelle Moureaux (a Tokyo based French architect and designer) spread distinctive bold colours across infrastructure – including steel beams and pillars, noise barriers, 13 stations and platforms, a bridge over the Tamsui River, and the exterior and interior design of the train. The platforms, walls and ceilings of Banqiao station are decorated by French artist Daniel Buren, using regular, contrasting coloured stripes.

Stations in operation

The western section of the line officially opened on 31 January 2020. After 3 April 2024, services between Zhonghe and Banqiao were temporarily suspended due to the 2024 Hualien earthquake. The repair work will take 1 year to complete.

Stations under construction

The north and south sections are approved for construction, which is currently underway. The estimated completion date for those sections is 2029.

South section

Stations Y01–06 are approved for construction. (Unopened stations' names are to be confirmed)

North section

Stations Y21–32 are approved for construction. (Unopened stations' names are to be confirmed)

Planned stations

The east section is still under planning and subject to change. After this section is complete, the Circular line will form a circle.

East section

(Unopened stations' names are to be confirmed)