東區海底隧道
In 1984, the government approved the construction of the Eastern Harbour Crossing, a tunnel to be used by cars and MTR trains. The Kwun Tong line was extended across the harbour on 5 August 1989 to Quarry Bay station, which became an interchange station for the Kwun Tong line and the Island line. An intermediate station, Lam Tin, started operations on 1 October 1989.