The North Island line is a proposal to provide rapid transit service for the area between the existing MTRIsland line and the northern coast of Hong Kong Island in order to relieve the already congested Island line. Originally, according to the document "Rail Projects Under Planning 2000" released by the Highways Department, the current Tung Chung line would be extended from Hong Kong terminus eastward and two new stations, Tamar station and Exhibition Centre station are proposed on the extension. The new route would then connect and continue on the Island Line from Fortress Hill station to Chai Wan terminus. The Tseung Kwan O line will have newly constructed tunnel connected from its North Point terminus to Tin Hau station without passing via Fortress Hill station and continue on the remaining western half of the Island line. In 2013, the Highways Department released a second option for the North Island line scheme, so-called the "interchange scheme" because it will only extend the Tung Chung line and the Tseung Kwan O line to meet at Tamar station where it will act as an interchange station for the two lines without dividing the Island line. The original scheme is known as the "swap scheme" for distinction.
On 21 February 2013, the Highways Department launched stage two of public consultation of Our Future Railway, and proposed two schemes for the North Island Line. In addition to a "Swap" scheme which was similar to previous proposals, the consultation documents also included a second "Interchange" scheme.
"Swap" scheme
The existing Tung Chung Line would be extended along the northern coast of Hong Kong Island, with Tamar, Exhibition Centre and Causeway Bay North stations along the route. The extension would then connect eastwards to the existing Island Line at Fortress Hill Station, and continue on the remaining Island Line section to Chai Wan Station. Concurrently, the Tseung Kwan O Line would extend from its current westbound terminus at North Point Station to the existing Island Line at Tin Hau Station, and continue on the remaining Island Line to Kennedy Town Station. As the diagram below shows, direct service between Tin Hau and Fortress Hill stations would be discontinued. This scheme would greatly increase the number of stations reached directly by the Tung Chung Line and the Tseung Kwan O Line on Hong Kong Island, but east-west directional traffic along the existing Island Line would be interrupted and require an interchange. Also, the maximum train frequency between Fortress Hill and Chai Wan Stations, which would be served by the Tung Chung Line, would have to reduce by 8 trains per hour because the service frequency of the Tung Chung Line is restricted by the capacity of the Tsing Ma Bridge. Also, the signalling system and rolling stock used on both lines are different, so the “swap” scheme was not considered in the plan. , West Island Line and South Island Line
"Interchange" scheme
Both the existing Tung Chung Line and Tseung Kwan O Line would be extended along the northern coast of Hong Kong Island. Three stations, namely Tamar, Exhibition and Causeway Bay North, would be constructed along the extensions, and either Tamar or Causeway Bay North Station would be chosen as an interchange between the two lines. This scheme would preserve the existing Island Line in its current form and would not change the current commuting pattern between the Central, Western and Eastern Districts. However, as the Tung Chung and Tseung Kwan O Lines would not be run on the Island Line, passengers would still need to interchange as they currently do. Also, this arrangement would be less effective than the "Swap" scheme in relieving congestion, since although the number of stations and the area served has increased, the link with the current Island Line would still be the same, unlike the "Swap" scheme.
2014 plan
According to the "Railway Development Strategy 2014" document, the government opted for the interchange scheme because its construction cost and difficulties are lower and it does not interfere with the commuting patterns of current Island line users. Construction is expected to begin in 2021 and finish in 2026. The cost is estimated to be HK$20 billion in 2013 prices. As of 2020, construction has not begun while technical design proposals are still under consideration.
