There are proposals to connect the Vestfold Line with the Sørlandet Line via a new Grenland Line. It would connect to the Vestfold Line just north of Porsgrunn Station and would run from Porsgrunn to Skorstøl on the Sørlandet Line. The line is estimated to cost NOK 20-26 billion and would allow the travel time from Kragerø to Oslo of 2 hours and from Kristiansand to Oslo in 3 hours and 23 minutes. Passenger trains along the Sørlandet Line, and possibly freight trains, would be routed via the Vestfold Line. It is therefore necessary to complete the upgrade of the Vestfold Line before the Grenland Line is opened.