In the longer term it will be a key component in the proposed Oslo to Hamburg high speed rail link via Gothenburg, Malmö and Copenhagen.

The tunnel is part of a larger project to upgrade the whole West Coast Line to double track.

However, construction was plagued by major difficulties concerning large amounts of water seeping in from surrounding rock, only a small fraction of which had been foreseen.

The main contractor, Skanska, took no special precautions for the sealant, nor did it tell its own workers or the local population of the risks.

Skanska, along with Rhone-Poulenc and Swedish Railways all had criminal charges brought against them; some senior executives resigned as a result.

[1] In 2005 construction resumed after a positive decision by the Riksdag and the Swedish government, hydrological and environmental remediation by Banverket and Skanska, and selection of contracting consortium Skanska-Vinci for the project.

Nicknamed "Åsa", the TBM was in reality a comprehensive tunnelling machine; as it drilled through the strata, it simultaneously installed precast concrete tunnel lining segments behind it, and then injected a mortar-and-gravel slurry into the voids between the strata and the lining.

Drilling then switched to the western tunnel, which started in March 2011 from the workface at the south end and proceeded north.

On 3 April 2012, this drive reached the central adit, whereupon 2,517 m (8,258 ft), or 46 percent, of the western tunnel had been bored.

Since the remaining cost at the beginning of 2005 was calculated to be more than SEK 4 billion, there was initially much debate and hesitation as to whether to halt or resume work.

On Nov 4, 2015 work was started to dismantle the old railway for re-use, recycling and disposal, and to rebuild the road surfaces at its crossings.