Since the 1980s there have been plans to upgrade the line to high speed. The first section, at Skoger, opened in 1995. It was followed by a section past Sande Station in 2001, a passing loop at Nykirke in 2002 and a section including the Jarlsberg Tunnel in Tønsberg in 2011. In 2016 a new railway through Holmestrand, of which most is in the Holmestrandsporten tunnel, opened. In September 2018 a new double track line between Larvik and Porsgrunn opened, which shortened the travel-time from 33 to 12 minutes.