But current lighting solutions have many drawbacks. They are usually mounted at the tunnel ceiling or high on the tunnel walls and therefore lead to complicated, lengthy and extremely expensive installation and maintenance work with prolonged closure times of the tunnel, which also leads to certain risks of accidents.
Insufficient illumination of the road makes it difficult for road users to identify the road boundaries, which increases the risk of accidents, for example because the road user keeps too much distance from the edge limit. Although the walls are partially illuminated, a “cave effect” can lead to claustrophobia and monotony, especially in longer tunnels, such as those found in the European neighbouring countries. This again significantly increases the risk of accidents.
Furthermore, the large amount of additional lights and signals for road boundary, emergency exits, escape routes, as well as other signs leads to a so-called “Christmas tree effect”: too much colored light information in different places irritates the driver, his concentration decreases. Finally, even in the event of a fire, the lighting is permanently affected by the rising heat and black smoke, what leads in most cases to a complete lighting blackout.