Input (grade 8): The northern section was completed on 30 September 1979 and opened on 1 October 1979.
Output (grade 5): The first line was opened in 1979. After almost four years, the northern section was completed on 30 September 1979. On 1 October 1979, the northern section was opened, with trains running from Shek Kip Mei to Kwun Tong.