The Quarry Bay Congestion Relief Works involved extending the Hong Kong Island end of the Kwun Tong Line from Quarry Bay to North Point via a 4.2–kilometre tunnel. The project was initiated due to overcrowding at Quarry Bay and persistent passenger complaints about the five-minute walk from the Island Line platforms to the Kwun Tong Line platform. Construction began in September 1997 and was completed in September 2001 at a cost of HK$3.0 billion (US $385 million). The tried-and-true cross-platform interchange arrangement is repeated here.