fɹʌm fˈoːɹ ˈeɪpɹəl nˈaɪntiːnhˈʌndɹɪd nˈaɪnti θɹˈiː tɹˈeɪnz ɐlˈɔŋ ðə sˈɑːɡnsvæn lˈaɪn wɜː kənˈɛktᵻd tə ðɪ ˈiːstɚn pˈɑːɹt ʌvðə mˈɛtɹoʊ, ɪnˈɪʃəli kənˈɛktᵻd wɪððɪ ɑːstˈɛnsdʒoʊ lˈaɪn.
From 4 April 1993 trains along the Sognsvann Line were connected to the eastern part of the metro, initially connected with the Østensjø Line.