entrance reading: (English: Tunnel closed). There are 15 turning areas which were constructed for buses and semi-trailers. In addition to the three large caverns, emergency niches have been built every . There are photo inspections and counting of all vehicles that enter and exit the tunnel at security centres in Lærdal and Bergen. There is also special wiring in the tunnel for the use of radio and mobile phones. Speed cameras have been installed because of serious speeding. There are very few other completely straight roads in the region. Air quality High air quality in the tunnel is achieved in two ways: ventilation and purification. Large fans draw air in from both entrances, and polluted air is expelled through the ventilation tunnel to Tynjadalen. The Lærdal Tunnel is the first in the world to be equipped with an air treatment plant, located in a wide cavern about northwest of Aurlandsvangen. The plant removes both dust and nitrogen dioxide from the tunnel air. Two large fans draw air through the treatment plant, where dust and soot are removed by an electrostatic filter. Then the air is drawn through a large carbon filter, which removes the nitrogen dioxide. Media gallery References External links World's longest Tunnel Page Aurland Lærdal Road tunnels in Vestland 2000 establishments in Norway Tunnels completed in 2000 European route E16 in Norway