is a series of underground expressway tunnels currently under construction between the Kungens Kurva interchange in the south of Stockholm and the Häggvik interchange north of Stockholm. Most of this bypass; more than 17 out of 21 kilometers, is built underground. The Swedish government decided to permit the construction of the bypass on September 3, 2009, according to the proposal by the Swedish Road Administration.
The bypass will become the world's longest tunnel in the proximity of a city. 140 000 vehicles per day are expected to use the bypass. The tunnel reaches at its deepest point 65 meters below sea level and the lake Mälaren. The projected cost for the project is estimated at 27.6 billion (short scale) SEK (2009 value). Construction began in August 2014 but was stopped for political reasons soon after but was restarted in early 2015 and is expected to take ten years to complete.