Tunnel Lighting

The maintenance of traffic volume at design roadway speeds through a tunnel on a bright sunlit day depends on the ability of the motorist to see the interior of the tunnel and objects on the roadway for a safe stopping distance. The geographic location, orientation, and portal surroundings influence the ability of the human eye to adapt from the bright ambient roadway to the “black hole” of the tunnel interior. The lighting of the tunnel interior to eliminate and or diminish the effect of the black hole is achieved through varied lighting concepts. The most prominent lighting concepts employed are the symmetrical and the asymmetrical, of which there are two types: the counter beam and line-of-sight. Linear or point source luminaires or a combination of types of sources are employed to provide for specific illumination requirements for unidirectional or bidirectional traffic tunnels as appropriate to the system.