The Oslofjord Tunnel is a long subsea tunnel which constitutes part of European route E134 and is hence part of the Trans-European road network. The tunnel traverses below Drøbaksundet of the Oslofjord, reaching a maximum depth of below mean sea level. The tunnel has three lanes, with one used as a climbing lane in the uphill direction to overcome the seven percent gradient. It has a speed limit of , which is enforced by traffic enforcement cameras. The tunnel has a width of and was at the time of construction build after criteria for a traffic of up to 7,500 vehicles per day.