Follo Line
The Follo Line () is a high-speed railway between Oslo and Ski, Norway. The line runs parallel to the Østfold Line, and is dimensioned for . Most of the line, , runs in a twin-tube tunnel named the Blix Tunnel, which is the longest railway tunnel in the country. Construction started in 2015, and the line opened in 2022. The Follo Line increased capacity from twelve to forty trains per hour along the South Corridor, and allows express and regional trains to decrease travel time from Ski to Oslo from 22 to 11 minutes. The line was projected to cost over 26 billion Norwegian kroner (NOK) in 2014, but the final cost became 36.8 billion NOK when it was completed. The project was a continuation of the Norwegian National Rail Administration's (now Bane NOR) plan to build four tracks along the three main corridors out of Oslo; the Gardermoen Line was completed in 1998, and the Asker Line was completed in 2011. Between 1989 and 1996, the Østfold Line south of Ski to Moss was upgraded to double track and higher speeds. To take full advantage of this and allow the rest of the Østfold Line to be upgraded for