Tunnel lighting is different from ordinary road lighting, because it must be lit 24 hours a day, and the lighting intensity during daytime is higher than the lighting intensity at night. It can be imagined that the electricity cost of the tunnel is an important part of the running cost; in addition, the tunnel lighting is different from general road lighting, and has its particularities obviously, including needs to consider driver’s adapt ability to daylight and shaded zone, the distance and luminance for the transition from daylight to shaded zone, etc. All these need to be taken into account in designing of tunnel lighting, moreover, it is related to the safety of tunnel users.
Entrance Lighting
1.Threshold zone: The threshold zone is to eliminate the “black hole” phenomenon, so that the driver can clearly identify obstacles at the threshold of tunnels.
2.Transition zone: The tunnel transition zone’s lighting is tasked with avoiding drastic change in luminance from the threshold to the internal, and its luminance level should be gradually decreased. Therefore, the lighting issue during daytime is more complicated than that at night.
Internal Lighting
The internal zone is the area within the tunnel away from the influence of natural light, and the drivers’ vision is only affected by the lighting inside the tunnel. The inner section is characterized of uniform illumination, because the luminance level doesn’t need to change at all through this zone, it only takes appropriate and stable luminance, of which the specific value is determined by the traffic flow and vehicle speed.
Exit Lighting
In a tunnel with one-way traffic, it is usually necessary to deal with the exit zone properly to alleviate the adverse effects of the white hole phenomenon; in a tunnel with two-way traffic, as it is entry at both ends, the lighting conditions are the same for the 2 ends, thus no need to deal with the issue of exit zone in particular.
In view of tunnel lighting’s characteristics against ordinary road lighting, generally the following aspects need to be considered in designing:
1.The basic luminance on the road;
2.Designed traffic speed, traffic volume, route straightness and other influencing factors on road;
3.Driver visual adaptation levels, especially at the entrance and exit of the tunnel; The larger the difference between levels of illumination is, the longer the duration of eye adaption takes. Under any given speed, the difference in illumination between in-tunnel and external environmental levels will be amplified, as that means the sensitivity in the distance he drives will be decreased in the driver’s vision system.
4.The basic luminance at tunnel walls;
5.Determined luminance level from the aspects of driving safety &comfort, etc.;
6. The hours of daylight. Human vision system cannot recognize the space-related details within the same length of time under different luminance levels.
To save energy, improve lighting effects , ensure driving safety and comfort in tunnel lighting, it need to consider from the following aspects as well,
a： Brightness
b： Brightness uniformity
c： Light glare
Different tunnels require different patterns of light distribution according to the site. The following are light distributions we recommend for common cases,
In addition, with variable wattage and optic options, ARDEN Lighting’s tunnel light ensure full compliance with tunnel automation systems. With infinite dimmable option, at least 25% savings in annual energy consumption can be achieved.
