The first bore of the SKr 10.5bn ($US 1.6bn) twin-bore tunnel between Bastad and Förslöv was holed through in August 2010. Tunnelling originally started in 1992 but was halted in 1997 when the project was one-third complete because of serious environmental concerns. Tunnelling restarted in 2005 and the project is now scheduled to be finished in 2015.

The tunnel is a key element in upgrading Sweden's West Coast Line between, replacing a steeply-graded single-track section on the line which is now 85% double-track. The tunnel will allow the number of trains to be increased from four to 24 per hour, while doubling the maximum permitted weight for freight trains. It will also allow the maximum speed of passenger trains to be increased from 80km/h to 200km/h.

The tunnel is being constructed by a joint venture of Skanska and Vinci, and involves the installation of around 40,000 concrete segments. Since being launched in autumn 2005, Åsa has drilled through a varied and unstable geology consisting of gneiss, amphibolites and dolorite. In order to drive the TBM through the Mölleback zone, a highly-decomposed and water-bearing fissure, a 230m horizontal rock section had to be frozen.