Running mostly underground, it passes through the southern part of Groruddalen, serving neighborhoods in the boroughs of Alna and Furuset.

The line is owned by Kollektivtransportproduksjon and operated by Oslo T-banedrift on contract with Ruter using MX3000 trains.

The line continues along the southern side of Tvetenveien and then passes into a tunnel through which it runs under named road and reaches Tveita Station.

After crossing under Ring 3 the line exits the tunnel and runs along the western side of Tvetenveien to Haugerud Station.

Operations are carried out by Sporveien T-banen on contract with Ruter, the public transport authority in Oslo and Akershus.

[8] On 15 September 1949, the Planning Office For the Suburban and Underground Lines was established as a division within the new municipality.

[9] The first specific plans were launched in March 1954, and consisted of four branches, including one on the south side of Groruddalen, which would be built to Furuset.

The plans originally consisted of terminus in the city center at Grønlands torg, with a possible extension to Nationaltheatret, where the line would intersect with Holmenkolbanen's light rails serving Oslo West.

The original plans called for the use of 600 to 650 volt (V) direct current (DC) fed via a pantograph, to allow comparability with the western light rail.

The system also took into use cab signaling and moving blocks, which were cutting edge technology at the time, and had only been implemented on the Stockholm Metro in Europe by then.

[13] The line was further extended to Trosterud on 15 December 1974, to Furuset on 19 February 1978, and finally to Ellingsrudåsen on 8 November 1981.

[17] In June 2010, the headway on the line was reduced from 15 to 7.5 minutes, with half the departures terminating at Stortinget.

[19] The Furuset Line has been proposed extended towards Lørenskog and Akershus University Hospital (Ahus), a distance of 5.0 kilometers (3.1 mi).

In addition, the Coca-Cola Company and Norway Post are both establishing workplaces for a combined 3,300 people in the areas of Visperud and around Lørenskog Station.

Akershus County Municipality has proposed building stations at Visperud, Lørenskog sentrum, Ahus and Lillestrøm.

[21] The cost of building the 4.8 kilometers (3.0 mi) from Ellingsrudåsen to Stovner is estimated at NOK 2.4 billion.