While there was a continual construction work from Oslo westward as far as Moi, the Jæren Line from Egersund to Stavanger in Western Norway was opened in 1878.

The railway line forms a horseshoe curve in the main valley -precisely the Kongsberg area -, passing Saggrenda to get back westwards.

While the main road E134 leads directly to Notodden, the southbound route forms a horseshoe curve in Ådalen before reaching Heddalsvatnet at Hjuksebø station on its eastern edge.

To the east of the lake, the route leads southwards, before the Saua river is bridged westwards at Akkerhaugen (in the former municipality of Sauherad) at its confluence with the Heddalsvatnet.

The line continues to Gvarv in the Gvarvelva valley, which we leave after calling at Bø (Telemark) southwards, going via side-valleys to Lunde, sitting at the Straumen river.