The Kolsås Line () is a line of the Oslo Metro. It branches off from the Røa Line at Smestad Station and runs through western Oslo and Bærum to Kolsås Station. It serves the neighborhoods of Ullernåsen, Øraker, Jar, Bekkestua, Haslum, Gjettum and Kolsås. It is served by Line 3 of the metro at a 15-minute headway. The section from Jar to Bekkestua is built as a dual system with overhead wires, allowing Line 13 of the Oslo Tramway to continue from the Lilleaker Line to Bekkestua every ten minutes.
The Kolsås Line was built as an extension of the Lilleaker Line. It had been built to Lilleaker in 1919. The line was extended to Avløs on 1 July 1924, and the line was extended to Kolsås on 1 January 1930. The line was initially owned by Bærumsbanen, which was bought by Oslo Sporveier in 1934. A connection to the Røa Line opened on 15 June 1942, allowing the line access to the Common Tunnel. At this point the section from Sørbyhaugen to Kolsås was designated the Kolsås Line, while the section from Jar to Skøyen was retained as the Lilleaker Line. T1300 trains of the metro were introduced in 1982 and from 1995 it was linked with the eastern metro lines. The line was closed for upgrades to metro standard in 2006. It reopened in eight stages from 2008 to 2014. There are plans to extend the line to Rykkinn, Bærums Verk and Sandvika, although none of these have political priority.
Route The Kolsås Line branches off from the Røa Line after Smestad Station at a site previously occupied by the now closed Sørbyhaugen Station. Sørbyhaugen is situated from Stortinget at an elevation of . Previously there was a station at Husebybakken. The line runs parallel to Ring 3, through four stations in Oslo: Montebello, Ullernåsen, Åsjordet and Bjørnsletta. Situated at elevation, Ullernåsen is the highest elevated station on the line. The line largely runs along Bærumsveien from slightly before Bjørnsletta.
At Øraker the Lilleaker Line meets the Kolsås Line, after which point the lines share tracks. The line crosses the municipal border across the river Lysakerelven. The now closed station of Lysakerelven, from Stortinget, was situated on the Bærum side of the municipal border between Oslo and Bærum. At Jar there are two sets of platforms, one for the metro and one for the trams. The continues past Ringstabekk, which is only served by the metro. It replaced three disused stations, Tjernsrud, Ringstabek and Egne hjem. Situated from Stortinget, Bekkestua is the terminal station for the tramway, and a major transit hub for central Bærum. Like Jar, it features two sets of different platforms. The shared rail section features both third-rail power supply and overhead wires. The trams have a narrower loading gauge and shorter platforms, making it necessary to provide separate platforms for them.
The line continues past Gjønnes and Haslum to Avløs, which is one of the three Oslo Metro depots. After that point, it passes through the stations of Valler to Gjettum and Hauger before reaching the terminus, Kolsås Station, which, situated from Stortinget, is the terminus of line 3 and the station furthest away from the centre of Oslo.
Service
The Kolsås Line is served by Line 3 of the metro. During regular hours, is operates at a 15-minute headway. It runs along the Røa Line from Smestad to Majorstuen and onwards in the Common Tunnel through the city center. East of the center the Line 3 continues along the Østensjø Line to Mortensrud. Travel time from Kolsås to Smestad is 22 minutes, and from Kolsås to Stortinget is 30 minutes. Operations are carried out by Sporveien T-banen on contract with Ruter, the public transport authority in Oslo and Akershus. The infrastructure itself is owned by Sporveien, a municipal company. Service is provided using MX3000 three- and six-car trains. In 2002 the stations along the line had an average weekday 8,568 boarding passengers. Bekkestua was the busiest with 1,126 daily boarding passengers, while Lysakerelven had the least with 235.
Jar is also served by Line 13 of the tramway. It branches off on the east side of Lysakerelven and follows the Lilleaker Line to Skøyen, where it continues as a street tram to the city center along the Skøyen Line. It operates at a ten-minute headway. Travel time to Jernbanetorget is 31 minutes from Bekkestua. In comparison, the metro uses 22 minutes from Bekkestua to Jernbanetorget. Tram operations are carried out by Sporveien Trikken using SL95 trams.
History
Background Bærum grew as a suburb of Oslo after the Drammen Line of the Norwegian State Railways opened through the southern part of the municipality in 1872. The areas around the railway stations became popular among the middle class, while the lower class started to settle further north. In particular the areas around Nadderud and Presterud received working-class populations. The construction of the settlements were often organized by trade unions. Local investors applied in 1897 to establish a tramway that would run parallel to the Drammen Line from Oslo to Sandvika—which at the time was steam-hauled, narrow gauge and single tracked and suffered from low regularity. The application was rejected by the Ministry of Labour in 1906 to avoid competition with the railway. Instead, the state started to modernize the Drammen Line by converting it to standard gauge, electrifying it and building double track.
Two proposals were issued in 1917 for a suburban tram line further north. The southern proposal was to build the line as an extension of the Lilleaker Line, which would open in 1919. The line would go from the initial terminus at Lilleaker and extend towards Jar and Nadderud to Haslum. The northern proposal was for an extension of the Røa Line (at the time called the Smestad Line) via Røa to Hosle, Haslum and Fleskum to Kolsås. The latter was essentially a combination of the current Røa and Kolsås Lines. The two proposals caused local debate; generally people in western Bærum in general supported the northern line and people in eastern Bærum supported the southern line. An agreement was quickly reached with Kristiania Elektriske Sporvei (KES), the owner of the Lilleaker Line. The municipal council voted in favor of the southern line in 1921 after first rejecting a proposal to negotiate trackage rights with Holmenkolbanen. The main argument for the southern alternative was that the municipality would not have to pay any of the investment costs for the section of the line that would be localed within Aker.
KES' operations in Oslo were municipalized in 1924 and became Oslo Sporveier. However, the Lilleaker Line was kept outside the expropriation. The expansion to Bærum was financed in part by the cash from the sale of the rest of the company and in part from free land from the municipality. Concession from Lilleaker to Bekkestua was granted in 1922, and on 28 December Bærum Municipal Council approved to extend the line from Bekkestua to Haslum. The line to Bekkestua opened on 1 July 1924 and the extension to Hslum on 4 November. KES rebranded itself and became Bærumsbanen. The company bought twelve Class A trams and twelve trailers from Zypen & Charlier of Germany. After running along the Bærum Line to Skøyen, the trams continued along the Oslo Sporveier-owned Skøyen Line to Athenæum in the center of Oslo. Each station was equipped with a small building where there was a kiosk, telephone, ticket sale and freight handling.
The depot was originally planned to be situated at Haslum, but a more suitable lot was found at Avløs. A subdivision with dwellings for 39 employee families was also built there. On 27 August, the ground around Bekkestua started to sink; the track was lifted and covered with stone. Two days later, the track had sunk into the ground and a small island was created in a nearby lake. It turned out that the area was resting on clay that had transformed to quick clay after a water pipe had broken. It took two weeks to repair the damage. It became clear in 1924 that Bærumsbanen would also have to operate city services along the Skøyen Line in Oslo. This caused the company to order three trams and trailers, this time from Skabo Jernbanevognfabrikk. At the time it cost NOK 0.15 to take the tram within the city limits of Oslo, and NOK 1 from the city to Bekkestua. Passengers carried out a strike in 1924; this resulted is slightly cheaper tickets, but at the same time the trams and stations were equipped with advertisements.
Kolsås extension
The initial plans called for an expansion from Haslum to Kolsås. It was originally planned to run past Bærum Hospital to Løken Farm, but lack of funding instead forced the company to build the line along a cheaper section about one kilometer (half a mile) from the hospital. The free land for the extension was only valid for a limited time, and to be able to construct the line before the deadline, a single-track solution was chosen. The plans were passed by the municipal council in 1927 and concession granted on 10 February 1928. Construction started immediately, followed by track laying commencing in June 1929. The extension opened on 1 January 1930. Valler Station had a passing loop and at Kolsås a balloon loop was built. The line caused the closing of the bus from Haslum to Bærum Hospital, and the bus from Lommedalen was rerouted to correspond with the tram at Kolsås.
A mixed route scheme was introduced, where full-service trams operated all stations from the city center to Jar, while express trams would only serve boarding passengers from Athenæum to Tjernsrud. The full-services ran every 12 minutes and the express services every 30 minutes. The full-service routes were reduced to a 15-minute headway in 1932, but a 15-minute headway was introduced to Bekkestua with the express service. During rush-hour, there was a 7-minute headway to Jar and additional services to Haslum.
One of the conditions for the concession of 1924 was that the line was to be connected to the Common Tunnel of the Holmenkollen Line. Oslo Municipality demanded that the company either turn its trams at Skøyen or allow the municipality to purchase the company cheap. Bærumsbanen was bought by Oslo Sporveier on 1 October 1934 and turned into a subsidiary. The two companies had a common executive management, but retained separate operations. At the same time, Aker Municipality's tram company Akersbanerne was left operating a single line east of the city center, the Østensjø Line. In 1936, it was decided that Bærumsbanen would take over operation of this line, by operating the trams from the Kolsås Line through the city center to connect with the Østensjø Line. Operations started on 4 January 1937, and the service was marketed as the Østensjø–Bærum Line. Although Bærumsbanen took over Akersbanerne's three Class A trams, up to three units from Ekebergbanen were also leased.
Underground connection Since the birth of the line, plans had existed to connect to the Common Tunnel of the Holmenkollen Line. The tunnel would allow the trams to operate straight to the city center at Nationaltheatret, giving faster travel times and removing the heavy Class A trams from the city streets. A plan for the route from Jar to Sørbyhaugen on the Røa Line had been made in 1919, but by the 1930s, the Norwegian Radium Hospital and a tuberculosis hospital at Ullern had been built in the immediate vicinity of the line. Concession for this route was granted on 30 April 1937, but Aker Municipality protested, because they did not want noise pollution at the hospitals. Another concern was that the magnetic field from the overhead wires could affect the instruments at the hospitals. The route was therefore moved, but this made construction more difficult due to worse geological conditions.