8) The North Island line is a planned extension of the Tseung Kwan O line that will interchange at the future Tamar station with the Tung Chung line. It will alleviate traffic in the northern part of Hong Kong Island. There will be three new stations: Tamar, Exhibition Centre (which will be an interchange between the North Island line and the North South Corridor), and Causeway Bay North. Construction is expected to begin in 2021 and finish in 2026. The cost is estimated to be HK$20 billion in 2013 prices.