The Lærdal Tunnel in western Norway is the world's longest road tunnel, with a total length of 24.51km (15.23 miles). It has held the Guinness World Record since it officially opened on November 27, 2000.
The tunnel connects the municipalities of Lærdal and Aurland along the E16 motorway. It was built over five years at a cost of around £120m to provide a reliable year-round road link between Norway's two largest cities, Oslo and Bergen.
Road link that replaced mountain crossings
Before the tunnel existed, travel between Oslo and Bergen was difficult. Drivers faced mountain roads that regularly closed in heavy snow, or had to rely on ferry crossings that could be delayed by poor weather.
In 1992, Norway's Parliament approved the tunnel plan. Construction began three years later, in 1995, and the tunnel opened after five years of work.
Engineering and safety features
The Norwegian Public Roads Administration oversaw the project, with construction carried out by its own teams and contractor NCC Eeg-Henriksen Anlegg AS. The Norwegian Geotechnical Institute helped oversee geological work.
Building the tunnel involved excavating more than 2.5 million cubic metres of solid rock using drill-and-blast methods. The interior was reinforced with sprayed concrete and rock bolts to make it safe for traffic.
To keep drivers alert during the roughly 20-minute drive, the tunnel is split into four sections separated by three large caverns, each about 6km (3.7 miles) apart. These caverns are wider than the rest of the tunnel, providing turning space for large vehicles, and are lit with blue and yellow lighting designed to resemble daylight.
The tunnel is also known for its ventilation system. It was the first road tunnel in the world to have its own dedicated air purification plant, using electrostatic dust filters and activated carbon filters to remove nitrogen dioxide and exhaust particles from the air.
There is no toll to use the Lærdal Tunnel, and drivers can travel through it at the 80km/h (50mph) speed limit, with the journey usually taking about 20 minutes.
