Located on the boundary of Rogaland and Vest-Agder counties, in Norway, Fv946 (Tronåsen) is one of the steepest roads in the world (25-33%). Use at your own risk. Not recommended for non-experienced drivers.
Located at the northern end of the lake Lundevatnet, the road is 5.4 km (3.35 miles) long and runs from a parking place (toilets) of European route E39 and ends at Bakke Bro (bridge), an old suspension bridge from 1844 crossing the river Sira. The road is asphalted in pretty bad conditions. It is narrow (only 2,5 - 3,5 m wide) and totally closed in winters.
Be prepared, this road is not for the faint of heart or ill prepared. The road is extremely steep (25-33 degrees) via 11 sharp and challenging hairpin turns. Many cars have to back up, since the engine becomes too weak and the reverse has the most favorable gearing. The road is closed for large vehicles and for cars with caravans or trailers.
This steep, narrow and winding road was completed in 1844 but was in operation since 1791. It suffers the harsh meteorological conditions of the area every winter. The Tronåsen road is occasionally open for small cars during the summer (from May, 1st). The road was used during the Rally Monte Carlo in 1931.