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 to Quarry Bay, which became an interchange station for the Kwun Tong Line and the Island Line. The extension was launched on 5 August 1989. An intermediate station, Lam Tin, started operations on 1 October 1989.