Finding a suitable solution involves a chain of responsibility including local planning departments, local residents, owners, lighting designers and installers.
The past 20 years has seen a dramatic increase in the number of sports facilities in our communities. The booming health and fitness sector and the fact that many people like to participate in their favourite sport on weekday evenings, after work, accelerated this. Lighting systems have become a normal feature of outdoor sports facilities and, therefore, our neighbourhoods.
Artificial lighting systems have greatly benefited the users of sports facilities but, in some cases, have caused disturbance and even distress to people living nearby. It is usually the light straying onto a person's property or entering via living room or bedroom windows that causes the most frustration. The amount of obtrusive light needed to cause annoyance will depend upon the external ambient lighting conditions. Light pollution falls into three categories: sky glow, light trespass, and installation brightness / glare.
This is the well-known halo effect seen above our towns and cities. What we see is the light that is directed upwards being reflected off moisture or dirt particles in the air. Upward light makes air-borne pollution visible, which reduces the visibility of stars in the night sky. Needless to say, this represents a considerable waste of energy and obscures natural beauty.
This is light which enters our homes or falls vertically on surfaces both inside and out.
This is the overall visual brightness when looking in the direction of the installation.
- Zone E1 Intrinsically dark areas - national parks and protected sites
- Zone E2 Low brightness areas - industrial and residential rural areas
- Zone E3 Medium brightness areas - industrial and residential suburban areas
- Zone E4 High brightness areas - city centres, town centres and commercial developments.
1. Choice based on preserving the existing environment.
2. Classify whole municipal areas by zones E1 to E4.
3. Define a future master plan for the use of light in the municipal area.
This creates an umbrella under which planning requests can be considered and monitored against clear performance criteria. It is this aspect that will produce one of the greatest challenges for local planning authorities, who are faced with integrating this new thinking with existing regulations and dealing with the contradictions it brings.
Another aspect to be considered is that of time restrictions in order that local residents are not disturbed at all hours of the night. Curfew hours can be set, for example between 23:00 and 06:00, a common sleeping period, during which lower light pollution limits come into force.
The daytime appearance of the lighting system can be disturbing. This can be the case where large floodlights and arrangements are involved, or where the column heights are far greater than those of the surrounding houses, buildings or natural vegetation.
At present there is no government legislation. This is due to the fact that, during the past ten years, many countries have developed recommendations for dealing with light pollution. Whilst these are all largely in agreement as to how to tackle the problem, the actual values recommended do differ according to local expectations of what is tolerable. Two industry recognised publications which provide a degree of guidance for the reduction of light pollution are the CIE 150:200 'Guide on the Limitation of the Effects of Obtrusive Light from Outdoor Lighting Installations' and the ILE's 'Guidance Notes for the Reduction of Light Pollution'.
Good lighting design must serve the needs of the users and meet the appropriate requirements of all external parties, who experience the lighting. The lighting designer will consider the most appropriate floodlighting equipment, column height and column locations in order to limit the amount of light pollution.
In general, the floodlights that will produce the most efficient lighting system for a given specification will also be those that effectively control spill or stray light as a they concentrate a higher percentage of their light directly onto the target area - the sports field.
These types of lighting systems tend to be specifically designed for sporting applications, where the performance of the reflector system, luminaire, lamp and control gear are optimally matched by the manufacturer to produce far higher performance than that of general floodlights. Just as light spill is a key issue during evening games, so too is the issue of conspicuous masts, which can visually spoil the daytime aesthetic.
The lighting designer should define the best performance possible to balance all needs, and to verify by measurement that the installed system is correctly aimed to deliver the intended results. Installation has to be done, therefore, in close cooperation with the installing contractor to ensure that the columns are placed in the correct position and that all floodlights are aimed and tilted to the intended design positions for optimal performance. Large 'protractor - scale' angle indicators at either side of the floodlight, or a simple aiming device, permits accurate aiming.
Once correctly installed, consideration also has to be given to the lamp replacement without compromising the original aiming position of the floodlight.
Solutions for dealing with or avoiding light pollution concern more than just the proper choice of lighting equipment. All those involved, from town planners to the final users, have a part to play, and always with the sensitivities of the local community in mind.
One such example of reduced spill and spray is the OptiVision 'flat glass' asymmetric floodlight, available from Philips, which produces approximately three times less spill light than previous asymmetric floodlights. It has a patented reflector system which delivers its highest peak lighting intensity at 60 degrees from the vertical and an excellent cut-off at 80 degrees from the horizontal while in a flat glass position.
By designing very compact reflector optics around the double-ended 2kW lamp and oversized fins for optimal cooling, Philips has succeeded in making OptiVision smaller and more compact than comparable 2kW floodlights. This compact size together with the OptiVision's low weight, windage and versatile mounting options also allows for less visually obtrusive columns to be designed.