Proposals for bridges were first made in 1988, as part of a joint planning of a new high-speed railway and freeway through Vestby.

Johs Holt were the structural engineers and Lunde og Løvset architects.

Its northern end is situated 46.02 kilometers (28.60 mi) from Oslo Central Station.

[2] The two western bridges carry a combined four freeway lanes of European Road E6.

The three concrete cantilever bridges have the same span and length dimensions, with pillars located at the same relative points.

[3] NSB changed their original plans and cut the initial double tracking short at Rustad Station so that the section south of Rustad could be moved and planned along with the freeway.

[2] The increased speed meant that a simple double of the existing track was no longer a viable option.

[10] Planning on this project was therefore carried out jointly between NSB and the Public Roads Administration.

Important aspects were construction costs, minimizing the amount agricultural land which was taken and esthetics.

[6] Several designs were considered, with a concrete cantilever and a steel box girder the two finalists.

The latter would have a smaller profile, with a girder height of 4.3 meters (14 ft), but the placement of the pillars would force the rerouting of the Såna.

The cantilever gave a stiffer construction and higher weight and would also be more dominant in the landscape.