The tunnel has two tracks, is electrified and allows for maximum speeds of 160 kilometres per hour (99 mph).

These are primarily intended to allow access for emergency personnel, rather than as an escape route for passengers.

[4] The line has two tracks, is electrified at 15 kV  16.7 Hz AC and allows for maximum speeds of 160 kilometres per hour (99 mph).

Prior to its opening, the only railway west of Oslo was the Drammen Line, which has limited capacity, and had a mix of local, regional, intercity and freight trains.

[13] The tunneling resulted in 800,000 cubic meters (28,000,000 cu ft) of soil, most of which was used for the expansion of the Port of Drammen.

This caused a land slip which pressed up soil nearby at Gjønnes Station on the Kolsås Line of the Oslo Metro (that section of the Kolsås Line was largely unused due to unrelated construction at the time); a 50 meters (160 ft) long section of one platform and track was pressed up 3 meters (9.8 ft), resulting in the other track lying on its side.

[14][15] Because of changes to European Union regulations after planning of the project, three extra emergency staircases had to be installed in late 2009.

To avoid similar problems which occurred during the construction of the Romerike Tunnel, where massive leaks took a year to fix, several test bores were made in the area to measure the groundwater level.

The measuring system was set up to communicate any indications of a change immediately & automatically to the on-site geologists, who would be able to act accordingly.

[22] Along with several other projects west of Oslo, including a new Lysaker Station and Høvik Station, and an upgrade to the Drammen Line between Lysaker and Etterstad, the Asker Line was meant to allow for higher service frequency, higher regularity and faster trains west of Oslo after its completion.

[23] The higher capacity was exploited with a new high-frequency schedule, named Route Plan 2012,[24] following delivery of new Stadler FLIRT trains.