 After no investments on the tramway for seventeen years, new stock had to be bought, and Oslo Sporveier opted for buying seven used M-23 units from the Gothenburg Tramway in Sweden.In addition twenty-five SL79 trams were delivered in 1982–83, followed by an additional fifteen in 1987, introducing articulated trams into the Oslo cityscape.Another major goal of the metro was to connect the suburban lines on each side of the city through a tunnel, specifically the Common Tunnel.