The Ring Line ( or ) 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 -long line has three stations: Nydalen, Storo and Sinsen. Four-fifths of the line runs within two tunnels, with the 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. Planning for the line began in the late 1980s, and the city council approved the line 1997. Construction started in 2000; Nydalen and Storo opened on 20 August 2003, and Sinsen opened on 20 August 2006. The line cost to build and was financed through Oslo Package 2. The Ring Line is served by lines 4 and 5 of the metro, operated by Sporveien T-banen on contract with the Ruter transport authority. All lines operate each fifteen minutes. Nydalen and Storo are such located that trains in either direction use the same time along the loop, effectively giving a five-minute headway to the city centre. After the opening of the line, the areas around the stations have had increased urban redevelopment. The infrastructure is owned and maintained by the municipal company Sporveien. History By the 1960s, Oslo had a rapid transit network that branched out north-east and north-west from the city centre. In 1987, the western and eastern network were connected, and through-trains started operating between the two networks from 1993. Plans to make a second connection through the borough of Nordre Aker were launched by politicians in the 1980s. It was argued that this was cheaper than building roads, with the per-kilometre price being about a quarter of that for motorways. Some politicians also saw the Ring Line as an opportunity to close all parts of the Oslo Tramway, except the Ekeberg- and Lilleaker Line. Oslo Sporveier, the contemporary operator of the metro, started planning the line during the late 1980s. The plans would take advantage of the Gjøvik Line's right-of-way between Storo and Sinsen, while the section from Storo to Tåsen would have to be built in a tunnel. A projection for the line