Lærdal Tunnel: The World’s Longest Road Tunnel

In 1975, the Norwegian Parliament decreed it necessary to join the capital of Oslo with the country’s second-largest city of Bergen via a reliable all-weather land route instead of the circuitous collection of narrow mountain highways that closed in winter weather and fjord-crossing ferries that previously connected the two cities. The solution was a series of tunnels in Sogn og Fjordane county along what is now European Route E16, allowing traffic to run uninhbited while preserving the alpine environment of the region from further human encroachment. In 1992, Parliament authorised the completion of the final link in the route: a mammoth 24.51 km (15.23 mi) tunnel between the villages of Aurland and Lærdal that would not only run under an entire range of mountains but constitute the world’s longest road tunnel, dethroning the previous record holder, Switzerland’s Gotthard Road Tunnel, by some 8 km (5 mi).

Laerdalstunnelen

The Aurland entrance to Lærdal Tunnel. Source: BIL, http://commons.wikimedia.org/wiki/File:Laerdalstunnelen.jpg.

Lærdal Tunnel, the long, nearly straight road at the right of the map, cuts a straight path under the surface of Sogn og Fjordane county, replacing the twisting mountain road that now runs above it. Other new tunnels are seen on the E16 to the west of Lærdal Tunnel (the 1.36 km/0.85 mi Fretheim Tunnel, the 5.05 km/3.14 mi Flenja Tunnel, and the 11.4 km/7.1 mi Guvanga Tunnel), forming a complete all-weather link between Oslo and Bergen.

Construction began on Lærdal Tunnel in 1995, taking five-and-a-half years at a cost of 1.082 billion kr (US$113.1 million). Navigation satellites and laser guides were used to ensure that the two sides of the tunnel would line up together in the middle (a second, 2.1 km/1.3 mi-long tunnel was constructed from a side valley into the middle of the future Lærdal Tunnel site in order to ensure works could be conducted from four sides instead of two, speeding up the construction process). 5 000 separate dynamite blasts were used to excavate the 2.5 million m3 (3.3 million cu yd) of rock from the tunnel. To prevent the tunnel from collapsing due to the immense pressure from the surrounding rock, 200 000 rock bolts and 45 000 m3 (58 900 cu yd) of reinforced shotcrete were applied to the walls to equalise the stress.

The mountainous alpine terrain seen here is bypassed by the tunnel lying one kilometre beneath the surface. Keep in mind that this imagery is from the middle of summer.

With the massive length and depth of the tunnel (much of the tunnel is around one kilometre beneath the surface), a major concern was maintaining fresh airflow and disposing of the massive amounts of exhaust generated by vehicles. Surpringsingly, there is only one ventilation shaft, located approximately 6 km (4 mi) from the Lærdal end of the tunnel. Instead of constructing more shafts, the tunnel employs fans at either entrance to draw in air, as well as an air filtration plant installed in a short side tunnel 10 km (6 mi) from the Aurland end. Other safety measures include telephone call boxes every 250 m (820 ft) and fire extinguishers every 125 m (410 ft). Every vehicle that enters the tunnel is photo-catalogued upon entry in order to ensure they make it out the other end.

Lærdal Tunnel employs a number of features designed keep to drivers alert through such an otherwise monotonous, claustrophobic drive, including occasional slight curves and pullouts every half-kilometre. Drivers can see hundreds of metres ahead at any given point. The most interesting features of the tunnel, however, are the three artificial ‘caverns’ placed at equidistant intervals within the tunnel. Unlike the main tunnel, which is generally dark save for the white lights overhead, the caverns are lit up with blue and green ambient lighting with yellow lights at the fringes of the pullouts producing the false impression of a sunrise or ‘light at the end of the tunnel’.

Laerdalstunnel_cave

Source: G. Lotsberg, The World’s Longest Tunnel Page, http://www.lotsberg.net/data/norway/laerdal/007.jpg.

The Lærdal tunnel - Worlds longest road tunnel

Source: K. Rivenes, http://www.flickr.com/photos/sprengstoff72/2580638852/. Licensed under the Creative Commons Attribution-NonCommercial-NoDerivs 2.0 Generic licence.

If the sky is the limit, why aim for the stars?

Source: J. Martin, http://www.flickr.com/photos/sprengstoff72/2580638852/. Licensed under the Attribution-NonCommercial-ShareAlike 2.0 Generic licence.

Laerdal Tunnel

Source: E. MacPhillimy, http://www.flickr.com/photos/emacp/4336327547/. Licensed under the Creative Commons Attribution-NonCommercial-NoDerivs 2.0 Generic licence.

Below, a real-time trip through Lærdal Tunnel. Can you endure all 22 minute and 25 seconds?

Further Reading

Brekke, A. (2001). The world’s longest road tunnel: Laerdal – Aurland. Bergen Guide, 21 Juanuary 2001. Available at http://www.bergen-guide.com/538.htm. Accessed 24 August 2013.

CNN (2000). Norway opens world’s longest road tunnel. 27 November 2000. Available at http://archives.cnn.com/2000/TRAVEL/NEWS/11/27/norway.tunnel.reut/index.html. Accessed 24 August 2013.

Engineering.com (2006). Laerdal Tunnel. 13 October 2006. Available at http://www.engineering.com/Library/ArticlesPage/tabid/85/ArticleID/60/Laerdal-Tunnel.aspx. Accessed 24 August 2013.

Lotsberg, G. (2006). Laerdal – World’s longest Road Tunnel – Nov. 27 2000. The World’s Longest Tunnel Page, 21 November 2006. Available at http://www.lotsberg.net/data/norway/laerdal/tunnel.html. Accessed 24 August 2013.

Roadtraffic-technology.com (2012). Laerdal Tunnel – the world’s longest road tunnel, Norway. Available at http://www.roadtraffic-technology.com/projects/laerdal-tunnel/. Accessed 24 August 2013.

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