Tunnel

Much-used main roads and highways are increasingly channelled through tunnels and underpasses. Areas of dense population and more stringent environmental demands make this necessary. Land use can thus be minimised and the ever increasing level of traffic kept under control.

Traffic density and toxic pollutants in conduit areas mean high demands in terms of safety and service life for tunnel luminaires. A corrosive atmosphere due to exhaust fumes in reaction with road salting leads to a high degree
of dirt and grime inside a tunnel, resulting in especially high-grade materials such as stainless steel for housings and safety glass for enclosures being used. Protection rates such as IP66 and IP67 are typical.

Normal calculation programs used for example in the installation planning of streetlighting are not suitable for tunnel installations. The spacial conditions in a tunnel require the consideration of wall reflections. A bright illumination of wall surfaces is also important in communicating a feeling of safety to road users. For the lighting planning of a tunnel or for the making of an offer, Siteco calculate according to current norms.

The level of illumination as well as quality criteria for luminaires are defined according to country-specific standards.

Approach: Stretch of road immediately before a tunnel. Its length is equal to the stopping visibility. It must be possible to see inside the tunnel from here in order to drive in with a constant speed.
Entrance: Distance required for bringing the vehicle to a halt from the tunnel portal. The level of illumination is determined by conditions in the approach zone as well as the traffic conditions, and remains constant for half the visibility range. It is then reduced to 40% of the original value by the end of the entrance zone.
Transition Zone: Distance over which the luminance is reduced from the value at the end of the entrance zone to that inside the tunnel. A ratio of 1:3 must not be exceeded if the luminance is reduced
Interior: Distance between the transition zone and the exit zone.
During the day, interior lighting is required from the end of the transition zone to the tunnel exit. At night, the requirements posed on the level of illumination Lin must be higher than for a comparable stretch of open road in order to take account of the changed physiological conditions. The tunnel must be illuminated over its full length at night.
Exit: Distance over which the lighting conditions outside the tunnel have a significant effect on the tunnel distance by day. Adaptive lighting may be required here in some cases.

sample projections / planning examples in Relux