The section of railway which runs between Farriseidet and Porsgrunn is in the process of being replaced with a new, high-speed section. It will reduce travel time between Larvik Station and Porsgrunn Station from 34 to 12 minutes. Originally planned as single track with two passing loops, it was upped to double track with surveys showing increased traffic should the Sørlandet Line be connected to the Vestfold Line with the construction of a proposed Grenland Line. The segment includes seven tunnels with a combined length of and five bridges. Municipal zoning of the segment was passed in July 2010, with construction commencing in September 2012. Construction is estimated to cost NOK 5.3 billion and is scheduled for completion in 2018.