 The plans were approved by Parliament in 1916 . However , the decision concerning technical specifications was not taken by Parliament until 1923 , when it decided that the line was to be electric . The line was then estimated to cost NOK 14 @.@ 5 million — the increase caused by inflation during the First World War — of which NOK 1 @.@ 2 million was to be paid by the local governments . The line was to have tracks which weighed 25 kilograms per meter ( 50 lb / ft ) . The curve radius was set to minimum 150 meters ( 490 ft ) , although exceptionally 125 meters ( 410 ft ) was permitted . The steepest permitted gradient was 5 @.@ 5 percent ( 1 : 18 ) . 
