To transport the products to the coastal port at Skien, Norsk Hydro needed to build an extensive railway network.

Cargo was stored in tank cars and transported down the 16-kilometre (10 mi) Rjukanbanen to Mæl, where it was transferred to the Tinnsjø railway ferry.

It received a thirty-year concession on 17 July 1907 to build—with necessary expropriations—and operate a railway from Rjukan to Notodden.

The agreement meant the railway line would become a joint venture between the two, while operations south of Tinnoset would be performed by NSB.

From Tinnoset a corresponding train would transport them to Notodden, and after the Bratsberg Line opened, connections were available to Skien and Oslo Vestbanestasjon.

From 1907 an unmotorized barge named Tinnsjø was completed; the steam ship Skarsfos was used to haul it between the two railways.

She got a major overhaul in 1915 after the sister ship SF Hydro at 494 GRT was launched the same year.

[5][13] While built by Norsk Transport, from 1913 the Tinnoset Line was operated by NSB, and owned by Øst-Telemark Jernbaneaktieselskap.

A suggestion to expand the canal to allow coastal vessels access was scrapped in favor of a railway.

[14] The line connects Notodden with Grenland, including the cities of Skien and Porsgrunn and the ports at Herøya and Brevik.

Prior to 1949 the terminal station had a break-of-gauge, and Vestfoldbanen continued as narrow gauge.