On 28 December 1914 the Sagene Line was extended via Bentse Bridge to Torshov, where it intersected with the Grünerløkka–Torshov Line. This allowed KSS to start a circle service, which it named Sagene Ring and numbered 0. It initially used white signs for the counter-clockwise inside ring and green signs for the clockwise outer circle. Thus the service would run along the Sagene Line and then connect down along the Grünerløkka–Torshov Line. The headway was set to five minutes, which required eight trams per direction. At Sagene they took a five-minute break, and as long as they were on time passengers could transfer to the next tram and save the break.
