Kolsåsbanen
Encyclopedia
The Kolsås Line is a rapid transit
Rapid transit
A rapid transit, underground, subway, elevated railway, metro or metropolitan railway system is an electric passenger railway in an urban area with a high capacity and frequency, and grade separation from other traffic. Rapid transit systems are typically located either in underground tunnels or on...

 line on the Oslo Metro network of Norway
Norway
Norway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...

. It branches off from the Røa Line at Smestad
Smestad (station)
Smestad is a station shared by the Røa Line and the Kolsås Line on the Oslo T-bane system. Although the two lines continue to share track some time after Smestad, passing the former station of Sørbyhaugen which was also shared, they diverge before passing another station...

, and runs 12.2 kilometres (7.6 mi) to Kolsås
Kolsås (station)
Kolsås is the end station of the Kolsås Line on the Oslo Metro. The station, located in Bærum municipality, comes after Hauger, and is located from Stortinget....

; the terminus being 17.3 kilometres (10.7 mi) from Stortinget
Stortinget (station)
Stortinget is an underground rapid transit station on the Common Line of the Oslo Metro, Norway. It is located in the heart of the city center, next to Stortinget, the Parliament of Norway. The station is served by all six lines of the metro. At the street level, the station serves tram routes 17,...

. While the eastern part of the line is in Oslo
Oslo
Oslo is a municipality, as well as the capital and most populous city in Norway. As a municipality , it was established on 1 January 1838. Founded around 1048 by King Harald III of Norway, the city was largely destroyed by fire in 1624. The city was moved under the reign of Denmark–Norway's King...

, most of the line is in the neighboring municipality of Bærum
Bærum
is a municipality in Akershus county, Norway. The administrative centre of the municipality is the town of Sandvika. Bærum was established as a municipality on 1 January 1838. A suburb of Oslo, Bærum is located on the west coast of the city....

. The line is owned by Kollektivtransportproduksjon, while the trains are operated by Oslo T-banedrift
Oslo T-banedrift
Oslo T-banedrift AS is a limited company that is responsible for operating Oslo Metro , the rapid transit in Oslo, Norway. The company is owned by Kollektivtransportproduksjon that again is owned by the city council...

 on contract with Ruter
Ruter
Ruter As is the public transport authority for Oslo and Akershus, Norway. The company, organized as a limited company is responsible for managing, but not operating, public transport in the two counties, including bus, the Oslo Metro, the Oslo Tramway and ferries...

. The line is served by route 6, that continues through the city center into the Ring Line.

The line was opened to Avløs
Avløs (station)
Avløs is a station on the Kolsås Line on the Oslo T-bane system. It is between Valler and Haslum, 13.6 km from Stortinget. The station was opened 1 July 1924 as part of the tramway Lilleaker Line. Along with most of the line, Avløs has been closed for upgrades since 1 July 2006 and its...

 as part of the Lilleaker Line in 1924. It was extended to Kolsås in 1930, and from Jar
Jar (station)
-External links:*...

 to Sørbyhaugen
Sørbyhaugen (station)
Sørbyhaugen is a former subway station on the Oslo T-bane.The station was located between Smestad and Makrellbekken, and was opened when the Røa Line was created, as an extension from Smestad to Røa on 24 January 1935. From 1942 it was the point from which the Kolsås Line branched off of the Røa...

 in 1942. Since 1995, it has been part of the T-bane. The line has been closed since 2006 for upgrades, with the first section to Åsjordet
Åsjordet (station)
Åsjordet is a station on the Kolsås Line and Line 6 on the Oslo Metro system. It is located between Ullernåsen and Bjørnsletta, from Stortinget. The station was opened on 15 June 1942 when the line from Røabanen to Jar was completed....

 opening in 2008. Between 2006 and 2008 the terminus was at Husebybakken
Husebybakken (station)
Husebybakken was a metro station on the Kolsås Line of the Oslo Metro. Serving the neighborhood of Montebello in Oslo, Norway, it opened in 1942, when the connection line between Sørbyhaugen and Jar was opened. It was closed on 19 June 1961, but reopened from 31 July 2006 to 31 May 2008, when the...

. The upgrade is scheduled to be completed by 2014.

History

Background

Bærum started developing as a suburb of Oslo after the Drammen Line of the Norwegian State Railways was opened through the southern part of the municipality in 1872. The areas around the stations became popular among the middle class, while the lower class started to settle further north. In particular the areas around Nadderud
Nadderud
Nadderud is a district in eastern Bærum, Norway. It was formerly farmland under one of Bærum's larger farms, named Nadderud, but since the 1950s it has been built up with housing, several schools and sporting facilities. The best known facility, which has made the name Nadderud nationally known, is...

 and Presterud became populated with the working class, often by subdivisions being built by trade unions. In 1897, local investors applied to establish a tramway that would run parallel to the Drammen Line from Oslo to Sandvika
Sandvika
is the administrative centre of the municipality of Bærum in Norway. It was declared a city by the municipal council in Bærum on 4 June 2003.Sandvika is situated approximately west of Oslo. It is the main transportation hub for Western Bærum, and has a combined bus and railway station. Sandvika is...

—which at the time was steam
Steam locomotive
A steam locomotive is a railway locomotive that produces its power through a steam engine. These locomotives are fueled by burning some combustible material, usually coal, wood or oil, to produce steam in a boiler, which drives the steam engine...

-hauled, narrow gauge
Narrow gauge
A narrow gauge railway is a railway that has a track gauge narrower than the of standard gauge railways. Most existing narrow gauge railways have gauges of between and .- Overview :...

 and single track
Single track (rail)
A single track railway is where trains in both directions share the same track. Single track is normally used on lesser used rail lines, often branch lines, where the traffic density is not high enough to justify the cost of building double tracks....

ed and suffered from low regularity. The application was rejected by the Ministry of Labour in 1906 because they did not want competition with the railway. Instead, the state started to modernize the Drammen Line by converting it to standard gauge
Standard gauge
The standard gauge is a widely-used track gauge . Approximately 60% of the world's existing railway lines are built to this gauge...

, electrifying
Railway electrification system
A railway electrification system supplies electrical energy to railway locomotives and multiple units as well as trams so that they can operate without having an on-board prime mover. There are several different electrification systems in use throughout the world...

 it and building double track
Double track
A double track railway usually involves running one track in each direction, compared to a single track railway where trains in both directions share the same track.- Overview :...

.

In 1917, two proposals were made 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
Terminal Station
Terminal Station is a 1953 film by Italian director Vittorio De Sica. It tells the story of the love affair between an Italian man and an American woman. The film was entered into the 1953 Cannes Film Festival.-Production:...

 at Lilleaker
Lilleaker (station)
Lilleaker is a light rail station on the Oslo Tramway.Located at Lilleaker in Ullern, it was the terminus of the Lilleaker Line when it was opened in 1919 by Kristiania Elektriske Sporvei as an extension of the Skøyen Line...

 and extend towards Jar
Jar
A jar is a rigid, approximately cylindrical container with a wide mouth or opening. Jars are typically made of glass, ceramic, or plastic. They are used for foods, cosmetics, medications, and chemicals that are relatively thick or viscous...

 and Nadderud to Haslum
Haslum
Haslum is a district in the municipality of Bærum, Norway. Its population is 6,041. Haslum is noted for its medieval parish church, which is surrounded by a cemetery.-References:...

. The northern proposal was for an extension of the Røa Line (at the time called the Smestad Line) via Røa
Røa
Røa was a borough of the city of Oslo, Norway up to January 1, 2004, when it became part of the Vestre Aker district.Røa is also a suburb of Oslo, located approximately 7 kilometers away from downtown Oslo. It primarily consists of duplex houses and apartment blocks as well as single-family...

 to Hosle
Hosle
Hosle is a district in the municipality of Bærum, Norway. Its population is 5,713.-References:...

, Haslum and Fleskum to Kolsås
Kolsås
Kolsås is a wooded mountain ridge in the municipality of Bærum, Norway. Geologically, Kolsås belongs to the Oslo Graben area. Its two peaks consist of hard rhomb porphyric lava covering softer rocks, forming steep cliffs to the east, south and west....

. The latter was essentially a combination of the current Røa and Kolsås Line. The two proposals caused local debate with people in western Bærum in general supporting the northern line and people in eastern Bærum supporting the southern line. An agreement was quickly reached with Kristiania Elektriske Sporvei
Kristiania Elektriske Sporvei
A/S Kristiania Elektriske Sporvei or KES, nicknamed the Blue Tram , is a defunct operator of parts of the Oslo Tramway, Norway. It opened the first electric tramway in Scandinavia in 1894, and remained in service until 1924 when it was merged into the municipal owned Oslo Sporveier.-History:Tram...

 (KES), that owned the Lilleaker Line. In 1921, the municipal council voted in favor of the southern line after rejecting a proposal to negotiate trackage rights with Holmenkolbanen
Holmenkolbanen
A/S Holmenkolbanen was a company that owned and operated part of the Oslo Tramway and Oslo Metro in Norway from 1898 until 1975 when services were taken over by the majority owner Oslo Sporveier. Holmenkolbanen opened the Holmenkoll Line in 1898, and expanded it to become the first Nordic...

. 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
Aker, Norway
Aker is a former municipality in Akershus, which lends its name to a municipality and a county in Norway. The name originally belonged to a farm which was located near the current Old Aker Church...

.

In 1924, KES' operations in Oslo were expropriated
Nationalization
Nationalisation, also spelled nationalization, is the process of taking an industry or assets into government ownership by a national government or state. Nationalization usually refers to private assets, but may also mean assets owned by lower levels of government, such as municipalities, being...

 and became Oslo Sporveier
Oslo Sporveier
Kollektivtransportproduksjon AS is a municipal owned public transport operator of Oslo, Norway, the name meaning simply "public transportation producer". It operates the trackage and maintains the stock of the Oslo Metro and Oslo Tramway, as well as owning eight operating subsidiaries...

. However, the Lilleaker Line was kept outside the expropriation. The expansion to Bærum was financed in part by the cash from the sale and in part from free land from the municipality. Concession
Concession (contract)
A concession is a business operated under a contract or license associated with a degree of exclusivity in business within a certain geographical area. For example, sports arenas or public parks may have concession stands. Many department stores contain numerous concessions operated by other...

 from Lilleaker to Bekkestua
Bekkestua
Bekkestua is a town in the municipality of Bærum, Norway, with a busy bus terminal and a station on one of Oslo's westbound T-bane lines, Kolsåsbanen. It also has its own library, McDonalds, police station and fire station...

 was granted in 1922, and on 28 December the municipality voted 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
Bærumsbanen
A/S Bærumsbanen was a tram company that operated the Lillaker-, Kolsås and Østensjø Line of the Oslo Tramway, Norway, from 1924 to 1971 when the company became part of Oslo Sporveier.-History:...

. The company bought twelve Class A trams with twelve trailers from Zypen & Charlier of Germany. After running along the Bærum Line to Skøyen
Skøyen
Skøyen is a neighborhood of Oslo, Norway. It is located in the western part of the city, in the borough of Ullern.The name "Skøyen" comes from Old Norse Skǫðin, of unknown etymology....

, the trams continued along the Oslo Sporveier-owned Skøyen Line
Skøyen Line
The Skøyen Line is a tramway line running from Slottsparken to Skøyen in Oslo, Norway. It is served by line 13 of the Oslo Tramway. It connects the Briskeby Line at Slottsparken to the Lilleaker Line at Skøyen....

 to Athenæum
Wessels plass
Wessels plass is a square in Oslo, Norway, located south of the Parliament of Norway Building.-History:Originally on the site was a knoll with a house surrounded by a garden. The Parliament of Norway Building was completed in 1866, ad in 1873 Oslo municipality bought the knoll. It was demolished...

 in the center of Oslo. The stations had a small building where there was a kiosk, telephone, ticket sale and freight handling.

The depot was originally planned to be at Haslum, but a more suitable lot was found at Avløs. A subdivision for 39 employee families was also built at Avløs. 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 near-by lake. It turned out that the area was resting on clay that had transformed to quick clay
Quick clay
Quick clay, also known as Leda clay and Champlain Sea clay in Canada, is a unique form of highly sensitive marine clay, with the tendency to change from a relatively stiff condition to a liquid mass when it is disturbed. Undisturbed quick clay resembles a water-saturated gel...

 after a water pipe had broken. It took two weeks to repair the damage. In 1924, it became clear that Bærumsbanen was forced to also operate city services along the Skøyen Line in Oslo. This caused the company to order three trams and trailers, this time from Skabo Jernbanevognfabrikk
Skabo Jernbanevognfabrikk
Skabo Jernbanevognfabrikk was a mechanical workshop focusing on design and construction of railcars. It was established by Hans Skabo in Drammen, Norway in 1864; it became the first rail car factory in the country when it took delivery of the cars for Kongsvingerbanen...

. 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. In 1924, the company became subject to a passenger strike, resulting 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 initially 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 and the track laying started in June 1929. The 4.3 kilometres (2.7 mi) extension opened on 1 January 1930. Valler Station
Valler (station)
Valler was a station on the Kolsås Line on the Oslo Metro. It was located between Gjettum and Avløs, from Stortinget.The station was opened January 1, 1930 as part of the tramway Lilleaker Line....

 had a passing loop
Passing loop
A passing loop is a place on a single line railway or tramway, often located at a station, where trains or trams in opposing directions can pass each other. Trains/trams in the same direction can also overtake, providing that the signalling arrangement allows it...

 and a balloon loop
Balloon loop
A balloon loop or turning loop allows a rail vehicle or train to reverse direction without having to shunt or even stop. Balloon loops can be useful for passenger trains and unit freight trains, such as coal trains....

 was built at Kolsås. The line caused the bus from Haslum to Bærum Hospital to be closed, and the bus from Lommedalen
Lommedalen
Lommedalen is a picturesque, rural community in a small valley in Bærum municipality, in the county of Akershus, Norway. The population is about 3000 people. Its name is derived from the river Lomma, which, after joining with Isielva, forms Sandvikselva. Another explantion of the name, is by the...

 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
Tjernsrud (station)
Tjernsrud was a station on the Kolsås Line on the Oslo Metro system. Located in Bærum, Norway, it was between Ringstabekk and Jar, 9.9 km west of Stortinget...

. 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.

In 1924, one of the conditions for the concession was that the line was to be connected to the Common Tunnel of the Holenkollen Line. Oslo Municipality demanded that the company either turn its trams at Skøyen or allow the municipality to purchase the company cheap. On 1 October 1934, the Bærumsbanen was bought by Oslo Sporveier and made a subsidiary. The two companies had a common executive management, but retained separate operations. At the same time, Aker Municipality's tram company Akersbanerne
Akersbanerne
A/S Akersbanerne was a municipal owned company that operated tramways in the former Municipality of Aker in current Oslo, Norway. The company was established in 1917, and opened the suburban Østensjø Line tramway in 1926; it took over the majority ownership of Holmenkolbanen in 1933, that owned the...

 was left operating a single line east of the city center. 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 to the Østensjø Line. Operations started on 4 January 1937, and the 25 kilometres (15.5 mi) line 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
Nationaltheatret (station)
Nationaltheatret is an underground metro station and tram stop serving Vika and the city center of Oslo, Norway. It is located on the Common Tunnel of the Oslo Metro and on the Briskeby Line of the Oslo Tramway. Also located at the same place is Nationaltheatret Station of the Drammen Line. The...

, giving faster travel times and removing the heavy Class A trams from the city streets. A plan for the route from Jar to Sørbyhaugen
Sørbyhaugen (station)
Sørbyhaugen is a former subway station on the Oslo T-bane.The station was located between Smestad and Makrellbekken, and was opened when the Røa Line was created, as an extension from Smestad to Røa on 24 January 1935. From 1942 it was the point from which the Kolsås Line branched off of the Røa...

 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
Magnetic field
A magnetic field is a mathematical description of the magnetic influence of electric currents and magnetic materials. The magnetic field at any given point is specified by both a direction and a magnitude ; as such it is a vector field.Technically, a magnetic field is a pseudo vector;...

 from the overhead wires could effect the instruments at the hospitals. The route was therefore moved, but this made construction more difficult due to worse geological conditions.

Construction started in 1939, but was put on hold in 1940 because of the break-out of World War II. Construction commenced in April 1941 and later the same year the first Class C trains were put into service. The work also involved widening the profile between Jar and Egne Hjem
Egne hjem (station)
Egne hjem was a Oslo Metro and Oslo Tramway station on the Kolsås Line located in Bærum, Norway. The station is situated between Ringstabekk and Bekkestua, from Stortinget....

 so the Class C could operate on the whole line. The connection from Jar to Sørbyhaugen opened on 15 June 1942. From Haslum to Kolsås, the line was upgraded to double track; this opened on 23 December. The Class C was a class of eight larger trams that matched the width of Holmenkolbanen's lines. In addition, two Class A trams were converted to the wider and longer Class D.

With the opening of the connection, the 16.4 kilometres (10.2 mi) section from Sørbyhaugen to Kolsås was designated the Kolsås Line, and the 3.8 kilometres (2.4 mi) section from Jar to Skøyen was designated as the Lilleaker Line. A balloon loop was built at Jar, and the new Class B trams that served the Lilleaker Line could start turning there. This allowed for transfer between the two lines. The distance from Kolsås to Nationaltheatret was 16.4 kilometres (10.2 mi). During World War II, ridership on the whole tramway, including the Kolsås Line, skyrocketed. In 1938, the line transported 5.7&nsbp;million passengers, while in 1944 it transported 19 million. In 1944, the ownership of rolling stock and all but two employees in Bærumsbanen were transferred to Oslo Sporveier. However, the ownership of the tracks and the formal operation rights remained with Bærumsbanen.

Post-war operations

At the end of the war in 1945, the line was in need of a major overhaul, in particular the overhead wires. Lack of materials and money caused the extraordinary maintenance to take four years. Limitations of freight were imposed in 1946, and were terminated the following year. At the same time, the Kolsås Line services were internally numbered 14, but it was first many years later that the number appeared on the destination signs and schedules. In 1948, a former barracks was moved to Avløs where it was used as office space. Until 1951, the line had had constant fares since 1939; a 27 percent fare increase in 1951 was not sufficient to cover the 170 percent cost increase in the same period.

From 1949 to 1966, Avløs Depot built nine new Class C trams. In 1963, the line also received two Class T trams that were prototypes for the first Oslo Metro rolling stock
Oslo Metro rolling stock
The rolling stock of Oslo Metro, Norway has consisted of three classes: T1000/T1300, T2000 and MX3000. The T1000 was built as 162 single cars from 1964 to 1978. From 1979 to 1985, 33 new T1300 trains were built, followed by the conversion of 16 T1000s. Six two-car T2000 units were delivered in 1994...

. On 5 July 1957, Mærradalen was closed and Ullernåsen
Ullernåsen (station)
Ullernåsen is a Oslo Metro station located at Ullern in Oslo, Norway. It is on Kolsås Line between Åsjordet and Montebello. It was opened on 15 June 1942. Since June 2006 it was temporarily closed while Kolsåsbanen was upgraded, and reopened on 18 August 2008....

 was moved mid-way between its old location and that of Mærradalen. On 19 June 1961, Husebybakken
Husebybakken (station)
Husebybakken was a metro station on the Kolsås Line of the Oslo Metro. Serving the neighborhood of Montebello in Oslo, Norway, it opened in 1942, when the connection line between Sørbyhaugen and Jar was opened. It was closed on 19 June 1961, but reopened from 31 July 2006 to 31 May 2008, when the...

 was closed for traffic, due to low ridership and close proximity to near-by stations. During the 1960s, the rectifier
Rectifier
A rectifier is an electrical device that converts alternating current , which periodically reverses direction, to direct current , which flows in only one direction. The process is known as rectification...

 at Jar was replaced with a more modern one at Øraker and a new garage built at Avløs Depot. Since the 1960s, ridership lay stable at about four million passengers per year. From 1971, Bærumsbanen was liquidated and ownership and all aspects of operation of the line was transferred to Oslo Sporveier.

In 1978, Holmenkolbanen started taking delivery of the T1300 series of combined metro and tram multiple units. This caused Oslo Sporveier to put into service HKB 500 units on the Kolsås Line. To use T1300 stock on the Kolsås Line, several upgrades were needed: the platforms height
Railway platform height
On a railway the platform height refers to the height of a platform above the rail. The value varies between railway systems. A related term is "train floor height" which is the height of the floor of the rail vehicle. There are a wide number of standards for platform heights and train floor heights...

 was raised and the power supply was improved with new rectifiers at Ringstabekk and Kolsås. With the second delivery of T1300 stock in 1980 and 1981, the new units were put into service on the Kolsås Line. The T6 series of fifteen units was built with a driver's cab at both ends, so single-car trains could be operated in the evenings. This resulted in Class D being taken out of use in 1982. From 21 June 1982, the conductor was removed from the service. During rush hour, Class C units were still in use, and these still were manned with a conductor.

On 7 March 1987, Stortinget Station
Stortinget (station)
Stortinget is an underground rapid transit station on the Common Line of the Oslo Metro, Norway. It is located in the heart of the city center, next to Stortinget, the Parliament of Norway. The station is served by all six lines of the metro. At the street level, the station serves tram routes 17,...

 opened and Line 14 was extended further into the city center. This section was incompatible with Class C and these were retired. To meet the required number of trains, six T1000 units were converted to T1300. On 18 May 1995, the Røa Line from Sørbyhaugen to Volvat
Volvat (station)
Volvat is a disused rapid transit station on the Oslo T-bane.The underground station was located between Majorstuen and Borgen, and opened in 1939. The platform length was only large enough to accommodate two cars. When the Røa Line was upgraded to metro standard on 5 February 1995, it started...

 closed and the Røa Line upgraded to metro standard. At the same time, the Lillaker Line tram was extended from Jar to Kolsås. The upgrade involved the line receiving automatic train control
Automatic Train Control
Automatic Train Control is a train protection system for railways, ensuring the safe and smooth operation of trains on ATC-enabled lines. Its main advantages include making possible the use of cab signalling instead of track-side signals and the use of smooth deceleration patterns in lieu of the...

 with cab signaling, third-rail power supply and longer platforms. Until 20 August, Line 14 only operated between Kolsås and Montebello
Montebello (station)
Montebello is a station on the Kolsås Line of the Oslo Metro. The station is located between Smestad and Ullernåsen. Montebello is the first station on line 6 not shared with another line. The station is on the north side of the Ring 3 highway which runs in an arch north of Oslo...

. After the Røa Line reopened, the third rail had been laid to Montebello, and the trains had to switch power supply and signaling system there.

On 19 November, the Kolsås Line was connected with the Lambertseter Line east of the city center, given line number 4 and started operating through the city center. Oslo Sporveier decided that it wanted to remove the rush-hour services and instead introduced three-car trains. Because of this, all station platforms were extended in 1997, with the changes taking effect from 7 April. From 5 April 1998, the Kolsås Line was connected to the Østensjø Line and given number 4. From 21 March 1999, all T1300 stock were overnighted at Majorstuen Depot and Avløs was reduced to a maintenance center.

In 1995, the new T2000 stock that was bought for the Holmenkollen Line was tested on the Kolsås Line, but the lower voltage made operations impossible. At Gjønnesjordet the current was measured at 311 volt. From 4 August 1995, the current on the line was increased to 680 volt and from 3 March 1999 to 750 volt. The latter was done after the trams had been rebuilt to handle the increased voltage and this taken into use on the entire tramway.

Metro standard

On 1 July 2003, budgetary disagreements between local politicians in Oslo, Bærum and Akershus led to the closure of the Bekkestua
Bekkestua (station)
Bekkestua is a station on Kolsås Line of the Oslo Metro situated at Bekkestua in Bærum, Norway.Located between Egne Hjem and Gjønnes it is being served by the Oslo Tramway line 13 while the Kolsås Line is closed for upgrade...

 to Kolsås leg. It was temporarily reopened 22 November 2004. There was a debate about what standard the line should have; many Akershus politicians wanted to convert the section west of Jar
Jar (station)
-External links:*...

 to light rail
Light rail
Light rail or light rail transit is a form of urban rail public transportation that generally has a lower capacity and lower speed than heavy rail and metro systems, but higher capacity and higher speed than traditional street-running tram systems...

, that would operate along the Lilleaker Line.

In early 2006, Akershus County Council
Akershus county municipality
Akershus County Municipality is the regional governing administration of Akershus, Norway. The main responsibilities of the county municipality includes the running of 35 upper secondary schools...

 passed a upgrade of the line. The line will be upgraded to metro standard all the way to Kolsås. Metro standard is an upgrade to the line that will raise it to the same standard as the Røa and Sognsvann Lines have had since 1995. The overhead wire will be removed, and replaced by a third rail
Third rail
A third rail is a method of providing electric power to a railway train, through a semi-continuous rigid conductor placed alongside or between the rails of a railway track. It is used typically in a mass transit or rapid transit system, which has alignments in its own corridors, fully or almost...

; this will require the few remaining level crossing
Level crossing
A level crossing occurs where a railway line is intersected by a road or path onone level, without recourse to a bridge or tunnel. It is a type of at-grade intersection. The term also applies when a light rail line with separate right-of-way or reserved track crosses a road in the same fashion...

s to be removed. Station platforms
Railway platform
A railway platform is a section of pathway, alongside rail tracks at a train station, metro station or tram stop, at which passengers may board or alight from trains or trams. Almost all stations for rail transport have some form of platforms, with larger stations having multiple platforms...

 will be extended to accommodate six-car trains, instead of the former three-car limit. Signalling will be moved to inside the cabs, using automatic train control
Automatic Train Control
Automatic Train Control is a train protection system for railways, ensuring the safe and smooth operation of trains on ATC-enabled lines. Its main advantages include making possible the use of cab signalling instead of track-side signals and the use of smooth deceleration patterns in lieu of the...

. The metro standard will allow the new MX3000
MX3000
MX3000 is an electric train used on Oslo Metro in Oslo, Norway. The multiple units are produced by Siemens, who started serial delivery in 2007. Seventy-eight three-car units have been ordered by Kollektivtransportproduksjon, and five by Akershus County Municipality. They replaced the older T1000...

 stock to operate on the line. In addition, a light rail service will share the tracks between Jar and Bekkestua. The intention is to create a transport hub at Bekkestua enabling interchange with local bus services.

The upgrade will also reduce the number of stations. Lysakerelven
Lysakerelven (station)
Lysakerelven is a former station in western Oslo on the Kolsås Line of the Oslo T-bane network, between the stations of Bjørnsletta and Jar, from Stortinget. It was the last station within Oslo's boundaries before the line continues into Bærum; taking its name from the river Lysakerelven which is...

 and Bjørnsletta will both be replaced by a new station named Bjørnsletta
Bjørnsletta (station)
The old Bjørnsletta was a station on the Kolsås Line between Åsjordet and Lysakerelven of the Oslo Metro. It is located in the Ullern borough. Along with Frøen, Bjørnsletta was one of only two stations on the subway network which lacks step-free access to the platform.. The station was opened on...

, though located between the two. Similarly, Tjernsrud
Tjernsrud (station)
Tjernsrud was a station on the Kolsås Line on the Oslo Metro system. Located in Bærum, Norway, it was between Ringstabekk and Jar, 9.9 km west of Stortinget...

, Ringstabekk and Egne hjem
Egne hjem (station)
Egne hjem was a Oslo Metro and Oslo Tramway station on the Kolsås Line located in Bærum, Norway. The station is situated between Ringstabekk and Bekkestua, from Stortinget....

 will be replaced by a new station named Ringstabekk
Ringstabekk (new station)
Ringstabekk is a station on the Kolsås Line on the Oslo Metro system. Located in Bærum, Norway, it is between Bekkestua and Jar, 10.2 km west of Stortinget....

. In addition, the consulting form Norconsult
Norconsult
Norconsult is Norway's and one of Scandinavia's largest multidisciplinary engineering and design consultancies. The company was founded in 1929, and has its headquarters in Sandvika, just outside Oslo, Norway. Norconsult has about 1850 employees, of which about 400 work outside of Norway...

 proposed to replace the station Avløs
Avløs (station)
Avløs is a station on the Kolsås Line on the Oslo T-bane system. It is between Valler and Haslum, 13.6 km from Stortinget. The station was opened 1 July 1924 as part of the tramway Lilleaker Line. Along with most of the line, Avløs has been closed for upgrades since 1 July 2006 and its...

 with a new station called Durud, located 100 metres west of Avløs, but this has not been approved.

The line was closed on 1 July 2006, and the only operational station unique to the Kolsås Line was the new, temporary station Husebybakken
Husebybakken (station)
Husebybakken was a metro station on the Kolsås Line of the Oslo Metro. Serving the neighborhood of Montebello in Oslo, Norway, it opened in 1942, when the connection line between Sørbyhaugen and Jar was opened. It was closed on 19 June 1961, but reopened from 31 July 2006 to 31 May 2008, when the...

, which temporarily replaced Montebello
Montebello (station)
Montebello is a station on the Kolsås Line of the Oslo Metro. The station is located between Smestad and Ullernåsen. Montebello is the first station on line 6 not shared with another line. The station is on the north side of the Ring 3 highway which runs in an arch north of Oslo...

 from 31 July. Montebello was formerly the station where the metro switched from overhead wire to third rail. From 20 August 2007, Line 13 of the Oslo Tramway, that operates along the Lilleaker Line, was extended from Jar to Bekkestua, after a NOK 2.3 million upgrade to the line, and lowering of the platforms. From 16 February 2009, this service was trunkated to Lilleaker
Lilleaker (station)
Lilleaker is a light rail station on the Oslo Tramway.Located at Lilleaker in Ullern, it was the terminus of the Lilleaker Line when it was opened in 1919 by Kristiania Elektriske Sporvei as an extension of the Skøyen Line...

, following the closing of the stations from Jar to Bekkestua for upgrades.

In August 2008, the stations between Montebello and Åsjordet
Åsjordet (station)
Åsjordet is a station on the Kolsås Line and Line 6 on the Oslo Metro system. It is located between Ullernåsen and Bjørnsletta, from Stortinget. The station was opened on 15 June 1942 when the line from Røabanen to Jar was completed....

 were opened, after the upgrade was completed. The next section to be opened is the new Bjørnsletta, scheduled for 2010. The section from Jar to Bekkestua is scheduled for the following year. The final section to Kolsås is not estimated to be finished upgraded until 2014, after initial plannes had called for the upgrade to be completed by 2011. The project has received much criticism from users and politicians, since the metro line is being closed for eight years to allow an upgrade that takes 18 months to complete. Ruter has stated that the reason for the delays is a budget calculation error, that shows that the cost of upgrading is NOK 2.5 billion, and not NOK 0.7 billion. The error was made because the planners used price estimates for tramways instead of rapid transit.

While the Kolsås Line was closed, and the replacement trams drove no further than Bekkestua, a bus service—line 42—was set up to accommodate passengers all the way to Kolsås. It serves a slightly different sequence of stations. Starting at Majorstuen, stops are made at the demolished metro stations Volvat
Volvat (station)
Volvat is a disused rapid transit station on the Oslo T-bane.The underground station was located between Majorstuen and Borgen, and opened in 1939. The platform length was only large enough to accommodate two cars. When the Røa Line was upgraded to metro standard on 5 February 1995, it started...

 and Heggeli
Heggeli (station)
Heggeli is a former subway station on the Oslo T-bane.The station was located between Borgen and Smestad, and was opened when the Smestad Line was created, as an extension from Majorstuen to Smestad on 17 November 1912. It was closed as a part of the Røa Line overhaul in 1995.-References:...

 in addition to the stations normally served by the metro. From the junction at Smestad it follows the highway Ring 3
Ring 3 (Oslo)
Norwegian National Road 150, also known as Ring 3 and formerly Store Ringvei is a beltway limited-access road which circumnavigates Oslo, Norway. It runs from Ryen, through the Sinsen Interchange to Lysaker in Bærum.-History:...

, stopping at Montebelloveien and Radiumhospitalet. After leaving Ring 3 to follow the Norwegian National Road 160, the bus stops at Blokkajordet before reconnecting with the metro tracks to stop at Lysakerelven. In Bærum the stations Tjernsrud and Egne hjem were skipped due to technical reasons, instead adding three extra stops further west, at Løkebergveien, Bjørnekollen and Toppåsveien.
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