The Sognsvann Line is a rapid transit line on the Oslo Metro of Norway. It branches from the Common Tunnel at Majorstuen and runs 6.0 kilometers (3.7 mi) to Sognsvann. After Ullevål stadion, the Ring Line branches off. The Sognsvann Line serves the northwestern and northern neighborhoods of Oslo, mostly within the borough of Nordre Aker. The line is owned and maintained by Kollektivtransportproduksjon and has nine stations. The western end of line 5 serves the entire line. Line 4 and the eastern end of line 5 serve the southern part of the line up to Ullevål stadion before branching off and continuing along the Ring Line. This gives an average five-minute headway on the southern part and an average fifteen-minute headway on the northern part of the line.

The Ring Line is the newest rapid transit loop line of the Oslo Metro of Oslo, Norway. It connects to the Sognsvann Line in the west and the Grorud Line in the east; along with these two lines and the Common Tunnel, the Ring Line creates a loop serving both the city centre and Nordre Aker borough. The 5.0 kilometres (3.1 mi)-long line has three stations: Nydalen, Storo and Sinsen. Four-fifths of the line runs within two tunnels, with the 1.0-kilometer (0.62 mi) section between Storo and Sinsen, including both stations, being the only at-grade part. The line connects to the Grorud Line north of Carl Berners plass and with the Sognsvann Line north of Ullevål stadion.