fˈæst pˈæsɪŋ sˈɜːvɪsᵻz ˈɔːlweɪz jˈuːs ðə mˈeɪn lˈaɪn ɪf pˈɑːsᵻbəl ðɛɹ ɪz ɐ spˈiːd ɹᵻstɹˈɪkʃən ɔnðə lˈuːp.
Fast passing services always use the main line if possible - there is a speed restriction on the loop.