Tunnel east entrance with Toll Station Oslofjord Tunnel () is a subsea road tunnel under the Oslofjord, Norway, connecting Hurum, in Buskerud in the west to Frogn, in Akershus in the east.
Tunnel west entrance in Hurum
The Oslofjord Tunnel is one of the longest undersea tunnels of its kind in Northern Europe; it is 7.2 km long and reaches a depth of 134 metres below sea level, with a maximum gradient of 7%. The tunnel was opened by King Harald V on 29 June 2000, providing an alternative method of transport between the east and west side of the Oslofjord, replacing the former Dr bak Storsand Ferry operated by Ferjeselskapet Dr bak Hurum Svelvik.
The tunnel has one lane in each direction with an extra lane in the inclining direction on the slopes. The speed limit of 70 km/h is enforced by road rule enforcement cameras. The tunnel is partially toll financed with a toll plaza on the east of the tunnel.
The first suggestions for construction of a tunnel came with the suggestion of building a new main airport for Eastern Norway at Hurumlandet. Although Gardermoen was chosen instead as the location for the new airport, the plans for the tunnel were allowed to continue, and on 13 December 1996 the Norwegian Legislature authorized the project. Construction began on 14 April 1997. There have been some closings of the tunnel due to unstable geological activities.
da:Oslofjordtunnelen de:Oslofjordtunnel fr:Tunnel du Fjord d'Oslo no:Oslofjordtunnelen pl:Tunel Oslofjord