With the Fornebu Line (in Norwegian: Fornebubanen) project, all had started in a good way. The all-tunnel 8150 meter rail line is planned to connect of Fornebu in Bærum with Oslo Metro. It is also planned to have 6 stations. When completed, it will allow thousands of new housing development in the old airport area.

In the plans, the line would cost NOK (Norwegian Krone) 4,5 Billion. After various transport mode changes, construction has started in 2020. The current estimate is NOK 23,4 billion. More than 5 fold increase. Some even think this is very optimistic and the real cost will be around NOK 30 Billion. And there are even those think the ultimate price tag will even be much higher. Completion year has also shifted from 2027 to 2029.

https://www.nettavisen.no/okonomi/fornebubanen-koster-na-33-000-kroner-per-centimeter-marerittet-er-ikke-over/s/5-95-765620