It serves neighborhoods such as Smestad, Hovseter, Huseby and Røa in northwestern Oslo, and Grini, Øvrevoll and Østerås in northeastern Bærum.

The Røa Line is owned by Kollektivtransportproduksjon, and operated by Oslo T-banedrift on contract with the public transport agency Ruter.

It was built as a cooperation between the Municipality of Aker and the company Holmenkolbanen, and connected to the Holmenkoll Line's terminus.

The line was upgraded to rapid transit in 1995, became part of the metro and started running through the city center.

[1] Construction of housing in the Smestad area started after Kristiania Elektriske Sporvei (KES) established a tramway from the city center to Majorstuen in 1894.

In 1910, A. S. Guldberg, Iver Lycke, W. Munthes-Kaas and H. A. Mørk applied for a concession to build a tramway along the route.

The 1.9-kilometer (1.2 mi) long line was single tracked, with passing loops at Borgen and Smestad, which were the only stations in addition to Majorstuen.

The process had been delayed several times because of disagreements between the city and the company, in part because the two could not agree if it should be classified as a railway or a tramway.

It took five years to select a winner, and this allowed the municipality and company to make a compromise by locating the terminus at Nationaltheatret.

[5] The investments had drained Holmenkolbanen, particularly after it had received a massive lawsuit for damage to adjacent properties during the tunneling.

On 6 July, the section from Makrellbekken to Røa was upgraded to double track, and later Volvat was moved and placed inside a tunnel.

The main problem was getting building materials for a bridge to cross Grinidammen, and a local disagreement about where the station at Røa was to be located.

[11] During the early 1970s, Bærum Municipality wanted to extend the line onwards to Hosle, and were willing to pay the construction costs.

[12] Since 1978, Holmenkolbanen has had sufficient trams to operate an extension, but since then the municipality has not been interested in extending the line further.

Gradually during the 1970s and 1980s, Holmenkolbanen became more integrated into Oslo Sporveier, including the two using the same rolling stock, tickets and uniforms.

On 7 March 1987, the services from the west, including the Røa Line, were extended from Nationaltheatret to Stortinget, a station that allowed transfer to the metro.

The upgrades meant that all platforms needed to be extended to 110 meters (360 ft) to allow six-car metro trains.

The upgrade involved a complete renovation of the tracks, with the old ones being replaced with new, and increasing the weight to 49 kilograms per meter (33 lb/ft).

To compensate for the closing of Huseby skole, Røa was moved back to it original position, causing a heated local debate.

[1] The Røa Line starts at Majorstuen, a major public transport hub located 2.7 kilometers (1.7 mi) from Stortinget.

The line immediately enters a short tunnel, in which the now closed Volvat Station is located, 0.7 kilometers (0.43 mi) from Majorstuen.

Borgen follows next, located 1.5 kilometers (0.93 mi) from Majorstuen,[18] and serves a primarily housing area and a larger cemetery.

[23] Hovseter is a residential area with dominated by apartment blocks from the 1970s, and also serves Persbråten Upper Secondary School.

[23] The next station is Røa, located 4.8 kilometers (3.0 mi) from Majorstuen, which has also been a terminus for extra rush-hour trains.

[26] The next station is Eiksmarka, located 6.2 kilometers (3.9 mi) from Majorstuen, which until the late 1970s had the line's only spur, to allow ballast stone to be loaded from Franzefoss.

[28] Next is Lijordet, located 6.9 kilometers (4.3 mi) from Majorstuen, which serves Øvrevoll Galoppbane, the country's only gallop race course.

The metro and the line are owned by Kollektivtransportproduksjon and operated by Oslo T-banedrift on contract with Ruter.

[30] The line crosses into Bærum, but the entire metro system is within a single fare zone.

One possibility is also that the service be continued along the Kolsås Line and a new branch be built to Sandvika, the municipal center of Bærum.