The issues of light pollution are highly emotive and pertinent and we regularly hear the resounding negativity of terms such as sky glow, light trespass and energy waste. There are, however, several other effects that are often forgotten: crime reduction, safety and disruption to ecosystems.
What can we do as lighting designers and manufacturers to combat these potential problems?
When we commence work on an initial lighting scheme design, we have a plethora of products at our disposal, along with advisory information from technical documents such as the ILP guidance notes and BREEAM assessment methodology.
A holistic consideration encourages us to take into account a number of fundamental factors that should be considered on every scheme.
When deriving the appropriate lighting class we take into account crime levels, ambient lighting levels and traffic flow rates, therefore taking measures not to over-light a scheme from day one.
Thought must also given to the colour rendering index of the lamp that is to be used on the scheme as the CEN code allows the selected S Lighting Class to be reduced by one class if a white light source is specified.
Much of the street lighting in the UK is still equipped with low pressure sodium lamps. Although these lamps are fairly efficient in terms of the lumens per watt, they offer very poor control and cast a deep orange light that is a huge contributor to sky glow.
In contrast, the latest discharge lamps, such as the Philips CosmoPolis, have a compact arc tube, meaning the light produced can be tightly controlled using specific reflectors for this type of lamp.
LED lanterns should also be considered for appropriate projects. These again offer very tight optic control, meaning the light can be directed exactly where it is needed, rather than needlessly and wastefully illuminating the surrounding area.
Optics have evolved significantly through the years, so what might have been considered an efficient luminaire ten years ago would now be deemed inefficient by today’s standards.
Appropriate optics for a specific application must always be selected: a fitting suitable for a wide dual carriageway will not provide optimum distribution to a narrow single carriageway road or a car park application. Reflectors are designed to emit light in precise patterns and a dedicated road optic will direct the light onto the road surface and not into adjacent areas.
Often schemes are specified as requiring flat glass lanterns. Although this is advantageous since there will be zero upward light from the fitting, it should not be the sole consideration. It’s worth noting that a curved glass lantern will generally achieve greater column spacing, meaning fewer fittings, therefore lower power consumption and less light pollution overall.
DIMMING & SWITCHING
Dimming systems are becoming more common as the political argument over energy usage (and carbon reduction) heats up. The original dimming systems used conventional magnetic gear which was not only unreliable but, during the dimming process, offered little energy reduction as the magnetic ballasts absorbed significant power.
The latest dimming and monitoring systems available on the market use electronic ballasts, offering dependable control of the lanterns and genuine energy savings. These systems allow individual or a complete series of units to be dimmed or switched off during off-peak times.
Although systems such as these definitely save energy and reduce light pollution, there are many objections to their implementation due to fear that their use could lead to increased crime rates and traffic accidents. Therefore, balanced consideration needs to be taken when planning the implementation of dimming and it should only be used where safe and appropriate to do so in order to achieve equilibrium between safety, light pollution and energy savings.
The use of projectors, spotlights, uplighters and feature lighting is more widespread than ever before. A well designed scheme incorporating these fittings will add the finishing touches to a project but a poorly engineered scheme can look unsightly, be ineffective, waste energy and create unnecessary light pollution.
Careful consideration should be given to the use of uplighters in particular:
- Is their use justified?
- Do they actually add significant aesthetic quality to the project?
- What intensity is required?
- Would a low-energy marker light suffice?
We may not be able to avoid sky glow due to the inherent directional nature of this lighting practice but we can thoroughly evaluate the design intent before deploying uplighting solutions. This analysis allows us to be certain that their use is warranted in a project and provides the opportunity to ensure they are as energy efficient as possible.
It’s clear that while nobody advocates light pollution, it is impossible to eradicate it all together. However, by employing the latest technology available and implementing well designed schemes, we can ensure we don’t contribute unwittingly to the problem.
We’d be happy to discuss your specific lighting design requirement in order to apply both our technological expertise and wider appreciation of the associated aspects of public realm lighting for the very best result on your project.