From 29 May 1927, Line 13 was replaced with Line 12, and from 19 June, Line 9 became Line 17, which continued along the Ullevål Hageby Line on the other side of the city center.
29. maj 1927 blev linje 13 erstattet af linje 12, og 19. juni blev linje 9 til linje 17, der fortsatte ad Ullevål hageby-linjen på den anden side af centrum.