In 1966, the Oslo Metro opened as an upgrade of two existing suburban tramways, the
Østensjø- and
Lambertseter Lines (Lines 3 and 4). By 1970, the system was supplemented by the
Grorud- and
Furuset Lines. They only operated to the eastern suburbs. In 1987, the system was expanded to connect to the western network, that remained a suburban tramway with
overhead wires, two-car platforms and an inferior signaling system. In 1993, the
Sognsvann Line was converted to
metro standard, with the
Røa Line following two years later. When the order for the MX3000 trains was placed, the
Kolsås- and
Holmenkoll Lines still used overhead wires, and would not be able to use the new stock. Both systems were at the time being considered for conversion to
light rail systems, that would connect to the
Lilleaker- and
Ullevål Hageby Line, respectively. The old fleet of T1000 and T1300 consisted of 195 cars in eight series. The T1000 was the original series delivered between 1966 and 1978, while the T1300 was a later adoption built until 1987. The T1000 series had only a
third rail shoe, while the T1300 also had a
pantograph, and could be used on the Kolsås- and Holmenkoll Lines. In 1995, six two-car
T2000 units were delivered for the Holmenkoll Line. They were, at the time, proposed as a possible replacement for all the T1000 and T1300 stock, but were prone to technical problems. They featured both third rail shoes and pantographs. In 2005, the city council voted to replace all existing T1000 and T1300 stock with the MX3000, increasing the quantity by another 30 units. Two test units were delivered in October 2005, and the serial production started in April 2006, with the first deliveries in April 2007. With the delivery of the new trains, Oslo Sporveier received criticism that they had been disloyal to the old red color of the metro, and that they did not follow up on their former design concept from the 1960s through the 80s. During the first 30 days, two errors occurred: one in the closing mechanism of the doors, and one with a switch in the cab that was not water tight. However, it turned out that Oslo Sporveier had not been accurate enough in specifying the energy consumption of the trains, and the
rectifiers on parts of the line needed to be upgraded to supply sufficient power to the trains. During 2007, there were four incidents where the trains were not able to brake at stations. The worst incident occurred when a train slid from
Blindern down to
Majorstuen. Following the 2006 decision to convert the Kolsås Line to metro standard, Akershus County Council announced that they would order five units. In November 2006, the city government proposed that the maintenance of the new trains be
privatized. This resulted in protests from the employees, who performed a partial strike by refusing to work overtime. As a result, after a few weeks, the company lacked 57 trains to provide adequate service. The issue was solved when the socialist opposition parties along with the
Liberal Party agreed to postpone the matter until after all the new trains were delivered in 2009. As part of the agreement, a new limited company, Oslo Vognselskap, wholly owned by Sporveien, would take ownership of all metro trains and trams used by the operating companies Oslo T-banedrift and
Oslo Sporvognsdrift, the latter being the operator of the
tramway. Responsibility for the debt accumulated after buying the trains was to be managed by Oslo Vognselskap, while operation and management of the maintenance contracts was transferred to Oslo T-banedrift. In January 2008, an additional 15 units were ordered by Oslo Municipality, with an option for further orders later. This would allow all the eastern lines to have a 7-minute-30-second
headway on their services into the city center, instead of the current 15-minute headway. Trains would start using the
balloon loop located at
Stortinget, and the western lines would continue to have a 15-minute headway. Additionally, the trains serving the
Ring Line were extended to six cars, with a double train set. The order cost NOK 675 million. In addition, Akershus finalized their order for five units, costing NOK 240 million. Unlike the Oslo-owned units, Akershus' five units are owned by the transit authority
Ruter. The same year, the city council in Oslo decided to upgrade the Holmenkoll Line to metro standard, to allow six-car MX3000 trains to be the main mode of transport to
Holmenkollen during the
FIS Nordic World Ski Championships 2011. This allowed 9,000 people per hour to be transported to the sports venue. In 2009, the T2000 units were taken out of service, and on 22 April 2010 the last T1300 was taken out of service, making the MX3000 the only units in traffic on the Oslo Metro. The city council was considering ordering 15 additional MX3000 to replace the T2000, as an alternative for a NOK 50-million renovation. In November 2010, the
Accident Investigation Board Norway criticized the braking system of the trains. In 2009, there were 83 incidents where trains with locked wheels slid down steep sections of track. The Accident Investigation Board found that the metro had conducted insufficient testing of the braking system on steep slippery lines, had not adjusted the brakes satisfactorily, and had not maintained the trains and tracks sufficiently. In December 2010, Oslo Vognselskap ordered another 32 three-car units, bringing the total order up to 115 three-car units. The last trains would be delivered by 2012. There was political disagreement regarding the final purchase, with the
Liberal Party and socialist opposition securing a majority for the purchase, while the right-winged parties voted to order 19 units. The extra trains will make it possible to run all lines except the Holmenkollen Line (Line 1) with six-car lines, compared to a situation with only three-car trains on the
Lambertseter Line, the
Ring Line and the
Kolsås Line (lines 4, 5 and 3) would only use three-car trains. ==Specifications==