Østfold Line

The Østfold Line (Norwegian: Østfoldbanen) is a 170-kilometer (110 mi) railway line which runs from Oslo through the western parts of Follo and Østfold to Kornsjø in Norway. It continues through Sweden as the Norway/Vänern Line. The northern half is double track and the entire line is electrified. It serves a combination of commuter, regional and freight trains and is the main rail corridor in the south of Norway. The Follo Line runs parallel to the Østfold Line in tunnel. The Eastern Østfold Line branches off at Ski Station and runs 79 kilometers (49 mi) before rejoining at Sarpsborg Station.

The line opened as the Smaalenene Line (Smaalenenebanen) on 2 January 1879. Stations were designed by Peter Andreas Blix. It was the first railway in Norway to predominantly build bridges and viaducts with iron. The line underwent upgrades from 1910 through 1940 in which the section from Oslo to Ski received double track, the permitted weight and speeds were increased and the line was electrified. From 1989 to 1996 the section from Ski to Sandbukta received double track and the maximum permitted speed increased to 160 km/h (99 mph). Work since 2015 been under way to upgrade most of the line to high-speed, with the new tracks at least as far as Halden by 2030.