Operating as Metro Line 1, it is the route with the fewest passengers[1] and the only one still to have level crossings and short station platforms.

Since its upgrade ahead of the 2011 FIS Nordic Skiing World Championships, the Holmenkollen line has been powered by third rail and operated by single three-car sets of MX3000 trains.

However, there is a large amount of seasonal tourist traffic, and the line – climbing as it does to over 400 metres (1,300 ft) and providing views over Oslo – is an attraction in its own right.

If it met performance expectations, future orders could be made to replace the T1000 stock when the latter reached the end of its economical life in around 2000.

[5] On 22 October 1987, a fatal accident occurred when one of the old HkB 600 units suffered a catastrophic failure of its braking system, and rolled down the Holmenkollen Line, finally tipping over at Midtstuen.

One person was killed and four were seriously injured, leading to a safety inspection of the old teak cars used on the line; the HkB 600 units were withdrawn from service, but were reintroduced after some refits.

The high development cost was subsidised by the Norwegian government, who saw the project as potentially establishing a new industrial export product.

[7][8] In 1996, Arkitektskap made a proposal to extend the line from Frognerseteren to Tryvannshøgda, where there is among other things a skiing centre with 200,000 annual visitors.

In 2003, Oslo Sporveier started terminating the Holmenkollen Line trains at Majorstuen, thus allowing the other routes of the metro to use the capacity.

A year later, running the trains through the Common Tunnel were re-introduced, after ridership on the Holmenkollen Line fell drastically.

[11] On 25 May 2006, Oslo was awarded the FIS Nordic World Ski Championships 2011, which would be held at Holmenkollen National Arena.

[13] In order to allow increased capacity on the line, it would either have to be connected to the street tramway, or upgraded to metro standard.

Travel time would be slightly increased, in part because of more stops along the line, including serving the main campus of Oslo University College and the shopping area in Bogstadveien.

[18] In December 2008, Ruter stated that it was considering building a tunnel from the Holmenkollen Line which would run to the area next to the ski-jumping hill.

The proposal would have cost an additional NOK 260 million and involved the building of a new station, either underground or at ground level.

Locals have been opposed to this solution, stating that they fear children will run into the tracks and get a lethal current through them, and that the municipality chose to take a shortcut to get the line finished in time for the World Championships.

[24] Kollektivtransportproduksjon stated that procuring spare parts was becoming nearly impossible and that the small size of the series forced high maintenance costs.

Alternatively, the city council has been recommended by Kollektivtransportproduksjon to purchase five new MX3000 three-car trains for NOK 250 million.