The E134 crosses the Oslofjord in tunnel between Hurum in Asker and Vassum in Frogn, just south of Drøbak. This is the only fixed road link across the outer Oslofjord.

The tunnel opened on 29 June 2000, replacing the Drøbak to Storsand ferry. It was built in three years, and carries one tube with three lanes, with oncoming traffic in the same bore. At its deepest it lies 134 metres below sea level, and the steepest gradient is 7 percent.

The tunnel has a long record of closures, and winter storms and ice are a recurring cause. Statens vegvesen has studied a new fixed crossing, and the Oslofjordforbindelsen project is in planning. Until it arrives, check the status before you drive.