Which European route includes the world's longest road tunnel, the Lærdal Tunnel?

The Lærdal Tunnel is carried by European route E16 in Norway, so E16 is the European route associated with the world’s longest road tunnel.

The 24.51-kilometre tunnel connects Lærdal and Aurland in Vestland county. It forms part of the principal road connection between Oslo and Bergen, allowing motorists to cross beneath the mountains without relying on a ferry or tackling a difficult winter mountain crossing. The tunnel opened on 27 November 2000.

Engineers divided the tunnel into four driving sections separated by three large caverns. These chambers are illuminated with blue and yellow lighting to create a visual break and reduce the monotony of a very long underground drive. Emergency niches, turning areas and ventilation systems were built into the design, and an air-treatment plant helps remove dust and nitrogen dioxide.

E16 is not the tunnel’s name; it is the numbered international route that carries traffic through it. Other options such as E6, E18 and E39 are major European routes in Norway, but they do not identify the highway passing through the Lærdal Tunnel.