North Star Lighting Group - Tunnel Lighting Systems

As our road networks become more crowded, the use of tunnels and underpasses, to improve traffic flow and protect local environments from increased traffic exposure, is expanding.

Within tunnels, where maintenance access can be limited and corrosive atmospheric conditions are common, reliable lighting systems are critical, as is the need for absolute minimum maintenance operational requirements.

North Star Lighting's tunnel lighting systems aim:

• Firstly, to allow traffic to enter, pass through and exit the enclosed section safely
• Secondly, to do so without impeding the through-flow of traffic

These aims are achieved by the adequate illumination of the tunnel interior, which allows drivers to quickly adjust to the light within, identify possible obstacles, and negotiate their passage without reducing speed.

HIGHLY ENGINEERED OPTICS

North Star Lighting's development programmes employ specialised software to help develop highly engineered optics, to optimise lighting systems, and to allow our lighting engineers to provide maximum safety and comfort for tunnel users.

Lighting a tunnel is a complex and specialised task. North Star Lighting has developed dedicated lighting systems and services to assist planners from concept to implementation, management and servicing. While luminance levels are used for accurate theoretical assessment, illuminance is more often used in practice.

North Star Lighting's assessment studies, therefore, are executed using luminance values, with the results presented as illuminance values. It is commonly accepted in road lighting that, even with the most accurate calculations and modelling, there is a substantial difference between what the mathematical lighting conditions are and what each individual driver subjectively sees in reality. This is especially true for tunnel lighting, where such sharp contrasts in light levels prevail.

IN-HOUSE VISIBILITY MODELLING SOFTWARE

At North Star Lighting, we have addressed this problem head on. Continuous research and development has led to a more sophisticated and detailed understanding of lighting and its effects on vision.

Along with rapid advances in IT, this research has allowed us to develop dedicated in-house software, which combines mathematical models of physiological stimuli with conventional lighting modelling parameters to generate results that are, visually, as well as mathematically, accurate beyond alternative visual modelling techniques.

Thanks to an impressive number of variables, our software is a unique and accurate tool. It verifies the ability of a given lighting system to meet the visual criteria set by all national and international standards regarding detection of obstacles on the road, within the allocated time.

HELPING TUNNEL LIGHTING DESIGNERS AND TUNNEL USERS

Taking into account criteria from the tunnel exterior and interior, the software generates a table of Visibility Levels (VL) that shows the extreme influence of daylight on the values of VL on targets in the entrance and threshold zones of the tunnel.

Experiments demonstrate that the minimum level of visibility should have a value equal to, or greater than, seven to ensure detection of planar or spherical targets. Though in North Star Lighting's current calculations, the target size may not exactly represent a potential obstacle in a tunnel, they show the behaviour of light on real, multifaceted objects whose diffuse reflectance can be modified and therefore they represent a real visual scenario for tunnel users.

The design of the lighting systems needed for a tunnel is the job of experienced designers who define the scheme, the choice of the lighting system, the type and number of luminaries, and their appropriate light distribution. North Star Lighting's visibility software provides invaluable new input into the design of optics for tunnel fittings making it easier for designers to create lighting systems and light distribution schemes for tunnels that maximise the visual performance and comfort of users.