Prepared 27 April 2010 for Prof. Madhav Badani (URBP506, McGill University).
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In this paper:
Mechanism of sight
Rods and cones
Melanopsin, melatonin, and the circadian clock
Three qualities of vision
History: when, how, and why the night was conquered
Solid state lighting: LEDs
Other techniques and technologies
A precautionary approach
Practical obstacles and workarounds
Defining and evaluating risk
Cost benefit considerations
Terms of reference
EDITOR’S NOTE: view the companion slideshow presented alongside this research.
Ecosystems are not simple. They are systems. They are complicated, diverse, and susceptible to component and systemic failure when disrupted.
Private installations excluded, more than 20 million streetlights were in use in North America as of 2001 (Mizon 2002, 45–6). Of these, the lion’s share are still configured with luminaires that were not designed to shine an optimal amount of light and only where needed — namely, on surfaces directly below the illumination source. When that light shines beyond where it must — such as outward and upward from a luminaire — it generates a skyglow effect known by astronomers as light pollution and by biologists as photopollution and ecological light pollution (Longcore and Rich 2004, 191). Moreover, when that unshielded light shines brighter than it should, it also generates impairing glare. This glare adds to a skyglow that by 2001 “resulted in approximately 40 per cent of the United States population, one-sixth of the European Union population and one tenth of the World population” completely unable to see the night sky with use of their built-in night vision capabilities, “because its brightness is above the night vision threshold” (Cinzano, Falchi, and Elvidge 2001, 701).
These concerns inform the genesis of an illumination planning framework. As a cross-disciplinary concern, it can explore, evaluate, and develop a policy architecture for artificial illumination management that balances both desired aesthetic results and ecological limits. Stakeholders might be institutional or commercial, but increasingly it is the epidemiologists and ecological conservationists whose concerns are now being heard for the first time.
In this essay, I propose illumination planning as a complementary, but autonomous discipline for municipal and regional policymaking. Illumination planning can provide a novel and comprehensively informed approach confronting artificial outdoor lighting as a transparent, implicit, and neglected aspect of traditional planning policy. This paper features a review of literature across several disciplines which traditionally are not grouped together. This holistic overview is a wager of sorts: by bringing specialists under the same tent, I hope to challenge a better comprehension of how indiscriminate lighting practices implicate several relevant interests, including interests which cannot speak for themselves.
Illumination planning acknowledges the morphology of artificial lighting at night and its uniquely interwoven relationship with the social, cultural, economic, and ecological conditions that it creates. It is also ideally poised to inform new policy language for striking an equilibrium between transportation safety, public safety, aesthetic desires, and keeping light from bleeding beyond where it was meant to shine. Illumination planning can identify and advocate improved practices for special lighting situations and develop strategies to reduce artificial light at night’s negative impacts on nocturnal habitats and public health. The core to this, though, is that illumination planning can bear witness to the nocturnal ecosystem as a separate, distinct environment now beholden to and threatened with colonization by a species which is evolutionarily adapted to the bias of daylight.
Light’s relationship with nearly all life is a symbiotic one: it functions like a biological signal beacon and probably has ever since the earliest organisms emerged four billion years ago (Pauley 2004, 589). Light — sunlight, moonlight, starlight, bioluminescence, etc. — signals to different species when to rest, feed, reproduce, or take shelter. This is just as much the case for animals as it is for plants which regulate growth cycles depending on seasonal changes to light — or for animals living in total darkness which must rely upon bioluminescent signals for their reproductive survival (Horch et al, 2008, 87).
As the literature across several disciplines has agreed that circadian and biological functions are dependent on specific, predictable qualities of light and darkness, our proliferate approach to outdoor lighting must come under closer, more critical scrutiny. As outdoor light at night’s effects are disrupting indigenous habitats, seasonal migrations, entire nocturnal habitats and, with humans, increasing the risk for carcinogenesis, the urgency to remedy these effects supersedes the mere economic, social, and engineering interests acting against it — even though planned mitigation of excess light at night can generate economic, social, and quality of life benefits in addition to an ecological remediation process.
Mechanism of sight
Our vision lets us see in a variety of lighting conditions while many other species are limited to much narrower ranges — such as, for example, only in dim conditions. The eye detects and processes light into electrochemical signals for the brain to render into images and other biochemical triggers.
Eyes of all species are enriched with specialized cells called photoreceptors. These are able to detect different wavelengths of light, but the quality of light which can be seen is directly linked to evolutionary adaptation. For instance, human eyes are best adapted to view the green region of the light spectrum for discerning foliage variations, while the ability to see in the red region of the spectrum can be used to identify fruits embedded within that foliage (King 2005, 3). Unlike several bird and insect species whose photoreceptors can also detect ultraviolet light, we cannot see beyond violet or, at the other end, infrared light beyond red.
Rods and cones
The human eye’s two dominant photoreceptors facilitating vision are called rods and cones. Each of these contains specific photopigments that can detect different types of light entering the eye (Stryer 1996, 557). Rhodopsin — exclusive to rods — is most sensitive under dim lighting. Opsins are the class of photopigments exclusive to cones and are sensitized for either red, green, or blue wavelengths. Combinations of these trichromatic — literally, three-colour — signals enable our colour vision. The high concentration of cones in the foveal region of the human retina — that is, the centre field of view — makes acuity (sharpness) possible. Cones are used in daylight or artificial lighting where colour can be detected.
Cones lose their light sensitivity just above the luminosity of a full moon. At full moon or dimmer lighting conditions, only the rods are used. While the rhodopsin in rods are most sensitive to greenish-blue light, it is interpreted only as a monochromatic signal. This explains the phenomenon when colour seems to vanish as night falls or is entirely missing when inside a darkened room. Switching on bright lights in that room, however, will overload the rods, causing temporary light blindness until the cones can adjust and take over vision tasks. If the lights are shut off, it can take up to a half-hour for rods to become fully functional again. Nocturnal animals may only have rods (or, in addition to rods, a trivial number of cones). In an artificially lit area, this could impair or blind all sight. As predator, foraging could be compromised; for prey, it could result in greater vulnerability.
Melanopsin, melatonin, and the circadian clock
The eye is equipped with other photoreceptors. The most relevant for this discussion are the retinal ganglion cells located underneath rods and cones. Typically, ganglion cells transmit information from cones and rods to the brain via the optic nerve. A very select few of these, however, are specialized for detecting low levels of light and are sensitized with another photopigment called melanopsin (Brainard, et al. 2008, 380). Melanopsin is most sensitive to bluer light, but rather than aiding vision, its role signals to the brain’s pineal gland when to regulate the secretion and suppression of the hormone melatonin (Czeisler and Gooley 2007, 583). Melatonin is used by the body to initiate a series of restorative and neurochemical functions, including protection against certain cancerous activity, ageing effects, and neurochemical disorders such as depression (Navara and Nelson 2007, 218–9). These are reviewed later in this discussion.
Three qualities of vision
Our rods and cones allow for three distinct qualities of vision: photopia, scotopia and mesopia (Fotios, Cheal, and Boyce 2005, 272).
Photopia is cone-dependent vision, enabling the ability for many diurnal species — some whose eyes have few rods — to see colour and sharpness in brighter lighting. Scotopia is rod-dependent vision and the sole domain for many nocturnal animals — many whose eyes lack cones. Scotopia tends to be less sharp than photopia. This is partly because several rods are connected to a single ganglion receptor, which then must deliver that light information to the brain for imaging; cones, meanwhile, are far fewer in number than rods (for humans, a 15:1 ratio) and far more sensitive, because each cone is linked to its own ganglion receptor — allowing for a better quality of imaging in-formation to be forwarded to the brain (Boyce 2009, 46–8).
Mesopia, meanwhile, is a hybridizing of rod and cone vision and is used mostly around dusk, underneath streetlights at night, or in low indoor lighting levels (Rea, Bullough, and Akashi 2009, 21). Objects nearby a light source will appear in colour, while colour quality will tend to diminish the more those objects are moved back into the darkness. Mesopic vision is now a major topic of interest for lighting engineers, whose goals include establishing quantitative standards for properly measuring mesopic vision performance (Goodman 2009, 231–32). A thorough understanding of mesopic vision is key to determining the best visual performance capabilities and applying that knowledge to street lighting circumstances. As it relates to illumination planning, this may actually help to reduce overall luminosities without compromising the quality of illumination — thus mitigating impact on the nocturnal ecosystem.
What are the ecological impacts of artificial light at night? Rather than compare its presence against an index for “excessive” light at night — problematic and subjective in of itself — it may be most useful to evaluate its effects from a baseline of zero ambient artificial lighting even while human activity is present: regional blackouts could be such possible baselines. Unfortunately, urban areas would find this baseline difficult to identify without deliberately shutting off all lighting — both a complicated and controversial proposition. The importance of baselines — be it actual or estimated — acknowledges conditions for indigenous nocturnal ecosystems before anthropogenic lighting technology began to disrupt it.
While biology is an extremely diverse discipline, the underlying relationship each sub-discipline shares in this discussion is a mutual interest to fundamentally understand the mechanisms of how and to what degree artificial light at night — that is, all lighting geared for outdoor use — is disrupting, harming, or altogether extirpating different species.
Table 1 outlines a compact overview of the literature on how ecological impacts of artificial lighting at night appear to affect different nocturnal taxa. It is far from an exhaustive compendium, but it does underscore how this area of research only started to emerge over the last decade or so.
Research literature cautiously suggests links between chronic, artificial light at night exposure and biological disruptions which appear to enable certain types of cancerous activity and impairment of our endocrine system (Iyilikci, Aydin and Canbeyli 2009, 67). Circadian disruption to our endocrine system may be far more implicated in the welfare of public health.
Relationships between cancer activity in urbanized areas and light at night receives considerable attention from epidemiological researchers. A site-specific study in Haifa, Israel, featured a select group of women whose shift work jobs exposed them to regular exposure to artificial light at night. A “statistically significant” increase in breast cancer rates was detected, while a comparison of their lung cancer rates was unchanged from the general population (Kloog, et al. 2008, 78). The same research team changed scope slightly by comparing rates of prostate cancer in men against light at night prevalence and found “a significant positive association between exposure to LAN, electricity consumption and prostate cancer” but not with colon or lung cancers (Kloog, et al. 2009, 120). Using laboratory rats for another study, the researchers conclusively identified a direct relationship between “influence of nocturnal light” and “mammary carcinogenesis” — recommending the addition of melatonin-based supplements to counteract tumour activity (Cos, et al. 2008, 270). Black, et al., (2005, 11174) verified that the intensity of light at night exposure corresponds with the rate of growth with breast cancer: increased light at night levels inhibits melatonin secretion with corresponding increases in tumour growth. In a melatonin-specific study on pancreatic cancer, results confirmed that adding melatonin supplements behaved with an anti-oxidant effect and reduced the size of tumorous nodules (Ruiz-Rabelo, et al. 2007, 270–5).
Other health research beyond oncology similarly finds beneficial effects of melatonin availability, suggesting that melatonin’s role is not only a benefit, but possibly a vital regulator of maintenance activity in animal biology. A positive relationship between increased white blood cell activity in the presence of increased melatonin is supported (Peña, et al. 2007, 268). Likewise, melatonin’s effects on cardiac health appear to negatively influence higher blood pressure and ease stress on the cardiovascular system (Reiter, Tan, and Korkmaz 2009, S20). A study on rats exposed to Arctic lighting conditions of continuous light (and corresponding darkness) concurred generally that pineal functions are negatively affected during constant daylight periods, contributing positively to the metabolic syndrome linked with obesity, hypertension, and other ageing factors (Vinogradova, et al. 2009, 862–3).
Mortality rates for these identified risks to light at night disruption may be relatively minor compared to other public health hazards — radiation exposure, particulate matter, groundwater contamination, overexposure to ultraviolet light, and so on. But an exhaustive understanding is still emerging. The known risks suggest at least an urgency for err on the side of caution for an illumination planning policy approach — much the way public health campaigns began exercising precautions for avoiding second-hand smoke exposure before its full effects were completely understood. Potential public health costs wrought by excess light at night should be given due consideration when weighing a cost-benefit analysis for capital projects such as lighting infrastructure retrofits.
History: when, how, and why the night was conquered
Geologically speaking, outdoor lights flickered on only a fraction of a second ago. Anthropologically, this amounts to about ninety seconds (from the first modern humans a half-million years ago). While humans learnt to control the naturally-occurring light of fire as far back as the first modern Homo sapiens and possibly earlier, its use remained confined to cooking, protection from predators and — following the end of the Younger Dryas ice age — illumination with oil lamp technology (including candles) (Douglas 2001, 1; Koslofsky 2002, 743).
As a technical innovation of the Industrial Revolution, the integrated outdoor lighting system debuted in 1806 when the first coal gas lamps were installed in West London, an upscale district of the city (Bouman 1987, 12). Early attempts with candle lanterns during the late 1600s had tried achieving similar ends for police patrolling; while success was limited, it provoked the imagination for exploring street lighting as a public service (Koslofsky 2002, 754). Street illumination allowed merchants to keep shops open well after dark as wealthy citizens used that extra time of “day” for leisure while police could more effectively patrol streets for vice activities; soon after, these advantages sold other cities on adding their own gas lamp systems (Bouman 1987, 16). Decades later the electric arc light, a source several orders brighter than gas and immensely popular with the public, assured that street lighting infrastructure had secured its place in the urban fabric — expanding its reach with increased ubiquity by the twentieth century as more reliable incandescent light bulbs became commonplace (Nye 1990, 3).
As lighting technology evolved during the twentieth century, the emphasis on boosting output and standardizing measurements for luminance were the main drivers behind making streets brighter (Cuttle 2009, 10). In other words, it was more important for street lights to be as bright as possible than to concentrate on focussing the light already being emitted to where it would actually be used to its fullest (i.e., ground surfaces). While this increased both annoying and even disabling glare conditions, particularly on wet surfaces, the unprecedented brightness levels were positively associated with modernity and progressivism — several cities creating “White Way” districts where conspicuous acts of consumption could occur and be easily seen by others (McQuire 2005, 130; Nye 1990, 54). By the 1930s, the expansion of streetlight use was tied to the growth of automobile popularity and improved highway road systems (Boyce 2009, 79).
Gas discharge bulbs are a mainstay of contemporary street lighting. These began replacing incandescents in the 1960s as mercury vapour bulbs demonstrated a greater reliability and durability while offering a five-fold improvement in lumens per watt efficiency (Riegel 1973, 1288). Along with the greenish-blue (and ultraviolet) light of mercury vapour, low-pressure sodium (LPS) lights were also among the first gas discharge bulbs to be widely used for infrastructure lighting, particularly so in Europe. As environmental concerns over mercury contamination were raised, mercury vapour lighting was slowly phased from service during the 1990s and replaced with high-pressure sodium (HPS) lighting — recognizable by its orange-pink hue. Even so, other gas discharge bulbs may still use an amalgam which includes small amounts of mercury.
In recent years, the emergence of ceramic metal halide (CMH) lighting — a type of high-intensity discharge lighting recognizable by its whitish hue and used for both sporting arenas and retail parking areas — has offered an alternative to HPS lighting. Its relative resemblance to daylight, able to render colours more effectively, adds an aesthetic advantage over its gas discharge counterparts, while its efficacious performance — that is, its ability to generate a better quality of light optimized to human vision capabilities, watt for watt, versus HPS lighting — has improved its cost effectiveness over HPS lighting in terms of life cycle costs (Rea, Bullough, and Akashi 2009, 1).
LPS lighting, while still in use, is seen less often. This is due to two reasons. First is quality: because it is a monochromatic light, eyes can only see objects in an amber hue, while other colours such as red may be completely cancelled out and appear black (Fotios and Cheal 2007, 226). LPS lights emit an eerie glow seldom seen in nature, in turn raising aesthetic and usability complaints when used in residential and commercial areas (Royal Commission 2009, 3). Second, concerns raised by public safety agencies have moved to discourage their widespread use since, for instance, colour-keyed roadway information cannot be accurately rendered under the amber glow (Pauley 2004, 593). Nevertheless, LPS lights remain the most energy efficient gas discharge bulb available and is strongly advocated by both astronomers (who can filter out its specific, 589nm light wavelength) and herpetology conservationists (whose observations confirm that sea turtles are not attracted by it) (Crawford 2000, 18; Salmon 2006, 146).
Solid state lighting: LEDs
Light-emitting diode (LED) luminaires are emerging as an increasingly viable alternative — if not a possible replacement — to gas discharge lighting. The ability to easily manage both hue and the illumination coverage area of an LED cluster yields new opportunities to devise customized solutions presently difficult (or cost prohibitive) to achieve with gas discharge bulbs (Lerchi, et al 2009, 144). Its increasingly higher efficiency in lumens per watt performance, durability, performance consistency, and longer anticipated life cycle further presents a strong case for the incremental application of LED luminaires. As with Moore’s law for microchip improvements, Haitz’s law states “the light output of LEDs increases by a factor of 20 every 10 years, while the cost decreases by a factor of 10 over the same period of time” (Pacific Gas & Electric 2008, 20).
Perhaps most valuable is the capability of integrated LED luminaire designs to more precisely focus light output and to do so more evenly. A 2008 field study completed in Oakland, California, compared LED and HPS luminaires using the same city block to test both systems. The researchers’ findings support this new capability: “lower average illuminance levels measured under the LED luminaires do not denote inferior light performance; the LED luminaires maintained minimum light levels across all spacings while significantly [increasing overall uniformity] compared to the HPS” (Pacific Gas & Electric 2008, ES-1).
In other words, LED luminaires can be configured to shine more dimly than gas discharge bulbs, yet still provide equal or better quality lighting by evening out illumination levels throughout the luminaire’s projection area. By contrast, gas discharge luminaires tend to create very bright “hot spots” underneath the luminaire while fading somewhat logarithmically as reaches the periphery of its projection area.
Lighting quality is not only dependent on the luminance source. How that light is focussed and how reaches its destination depends on its luminaire. Boyce (2009, 38) describes the luminaire in broad terms as the part of street lighting which “provides electrical and mechanical support for the light source and determines the light distribution.” In short, the luminaire’s main function is to protect the light source from the elements, to direct light output through “reflection, refraction, or diffusion, individually or in combination” (Id.). Luminaires can either be functional or ornamental, but they ultimately must meet these basic criteria.
The design possibilities for luminaires are virtually limitless, but they must also be functional. Functionality traditionally referred to the basic protection of the light source within. For light pollution remediation, this conventional approach is no longer sufficient. Luminaire designs now have an active role in channelling where light can and cannot go. The Illuminating Engineering Society of North America (IESNA) adopted a classification system for defining luminaire projection cut-off values to help standardize the measurement of directional light emissions (IESNA 2007). The classification system is based on the amount of light projected from the luminaire, as broken down into pie-wedge segments [Figure 1]. From these wedges, different luminaire classifications are made. Three are explained below:
- Non-cutoff (NCO). This luminaire class has “a luminous intensity distribution where there is no limitation of luminous intensity above the angle having the maximum luminous intensity” (Boyce 2009, 81). Globe and “historic” styled lampposts, like that shown in Figure 1, are representative of non-cutoff designs, as they illuminate evenly at nearly every angle (save directly below). These directly generate light pollution, emit light outward and upward — causing glare, skyglow, and can cause temporary light blindness when directly looked at in dark conditions.
- Semi-cutoff (SCO). These are luminaires which emit light at and below the luminaire’s 90-degree plane, while light emitted above that plane makes up no more than five percent of the total light emitted (IESNA 2005a). In Figure 1, this is the “upright” zone. Perhaps the most common streetlight in North America, the “drop lens cobrahead” design, is an SCO luminaire. Like NCO luminaires, semi-cutoff designs contribute to light pollution and light trespass as some light shines directly into the sky, and they contribute to light trespass (e.g., light bleeding directly into a second-storey bedroom). Glare and temporary light blindness are also a problem. Given their sheer number, SCO luminaires are likely the dominant contributor of excess light at night.
- Full-cutoff (FCO). These are defined as “having zero luminous intensity at or above 90 degrees from” the luminaire “and no luminous intensity in the range 80–90 degrees from the downward vertical greater than 10 percent” of the total luminaire output (Boyce 2009, 80). In Figure 1, no light is visible from either the “upright” or the “very high” region. No light trespass or glare occurs. Because light is only directed to where it is actually needed, FCO luminaire designs are an essential part of an effective light at night remediation strategy.
Other techniques and technologies
New instruments for optimizing lighting output and energy consumption may assume an equal role to light sources and luminaire shapes. One promising proposal, Outdoor Site-Lighting Performance (OSP), would drive better luminaire design by creating a “box” where illumination is needed or required; this box doubles as an illumination measurement yardstick and as a clear “dividing boundary between public and private interests” (Brons, Bullough, and Red 2008, 203). OSP also confronts the problems of sky glow, light trespass, and glare by creating a methodology to allow these three by-products of poor artificial lighting to be measured with standard instruments (Id., 204). An OSP box might extend to sidewalks on either side of a street: anything inside that box (reaching no higher than the luminaires) can be illuminated; everything outside that box (i.e., private property) would not.
Telemanagement and adaptive lighting offer two more instruments for illumination engineers. Telemanagement allows for the stepped dimming of a series of streetlights from a remote site; stepped dimming can help reduce hydro operating costs once traffic diminishes late at night (Guo, Eloholma, and Halonen 2008, 158). Adaptive lighting is a similar technique, but the difference is that it enables individual luminaires to dim and brighten as needed; control over this system can also be networked and managed online, which can signal when a luminaire is faulty (McLean 2009, 55). If a bulb fails, then adjacent luminaires on either side can compensate through raw illumination increases.
A precautionary approach
Nocturnal ecosystems and individual organisms (including ourselves) appear to be at risk to excess light at night. How great these risks are is not yet fully known. Until definitive conclusions can be ascertained from more research, might it in the meantime to act sooner rather than later?
While peer review is an ongoing process, it nevertheless would be, according to Buchanan (2006, 215) “prudent to adopt a precautionary approach” and “limit exposure to artificial night lighting whenever possible while biologists continue to investigate the effects of lighting.” While his research is specifically concerned with anuran health, this basic idea is just as useful for other organisms. Circadian rhythms — entrained since time immemorial by evolutionary adaptations to daily light-dark cycles — are now being altered, sometimes with fatal effects. The commodity value of bird fatalities and other habitat depletions may be hard to monetize where no market exists, but this does not dismiss a responsibility to assume responsible stewardship over “the commons”. As lamented by Hardin (1968, 1248), “In a still more embryonic state is our recognition of the evils of the commons in matters of pleasure.” As noted earlier in this paper, the evolution of streetlights was driven in great part by the convenience to conduct business, commerce, and leisurely activity well after sundown. So artificial lighting at night may be qualified as an anthropogenic contaminant — even if intangible — unless or until the burden of evidence proves otherwise.
Advancing a precautionary approach would mean to assume a “safe minimum standards” tack that would, in effect, specify thresholds “below which ecosystems services or resources should not be permitted to fall” (Rockström et al 2009, 9). In this sense, illumination planning can establish the core methodologies, conventions, and policy models to illuminate only intended surfaces, while areas beyond this would be strictly excluded from that light. It is unlikely that voluntary reversion to darkness on streets will happen anytime soon, if at all. But illumination planning would present the means to assure that the quality of darkness at night avoids falling below a threshold considered acceptable to key stakeholders.
Practical obstacles and workarounds
Efficient use of artificial light requires providing an even luminosity across a targeted zone. There are two problems with this strategy: one, lighting engineers designate minimum required luminosity standards for the dimmest part of a luminaire’s coverage area; to achieve this, over-illumination is used to assure these minimums are met, if not exceeded (McLean 2006, 12). Traditional luminaires — including conventional street lights and decorative, heritage-themed lampposts — are typically not designed to direct illumination evenly across an area or illuminate only the areas needed.
Second, gas discharge bulbs are still the standard technology for most outdoor lighting. Because their light output steadily diminishes over time, new bulbs are designed to exceed minimum illumination standards by up to 20 percent to assure that they can maintain minimum compliance once they reach the end of their service lifetime (Guo 2008, 35). To over-design in this manner means entire areas are often far brighter than necessary. This also means that very old bulbs can dip below minimum levels which, placed next against a new installation, can result in very uneven lighting (Guo, Elohoma, and Halonen 2008, 164). These conditions in turn contribute to harsh illumination, skyglow, light trespass, and glare.
One approach may be to only use lighting systems which can limit these inconsistencies. Solid-state LEDs may help to solve this problem. Unlike luminaires for gas discharge bulbs, LED arrays in an integrated luminaire are not really confined to any single dimension. This flexibility can enable a design to provide illumination more evenly and only where that light is needed. An LED array might, for instance, be better able to project evenly across and parallel with the edges of a roadway (i.e., a rectangle). It would be possible to reduce total luminance by more than half that of a sodium gas-discharge light while still maintaining proper minimum levels at its periphery (Pacific Northwest National Laboratory 2009, 5.1).
Defining and evaluating risk
An interdisciplinary, systems based approach can bring together different perspectives, data, and findings to determine how best to evaluate risk. Fischhoff, Watson, and Hope (1984, 128) suggested that risk is a subjective judgement call — specifically, it must be determined “which consequences it should include,” meted by “’society’s values’, rather than any of those of any single interest.” This poses a chicken-egg paradox, given that society itself must first be apprised of the risks before it can be consulted on for general consensus on how to act on that risk.
Evaluating risk for artificial lighting is problematic, in that its value for urban activity is established by most as a net benefit (e.g., lighting roads to improve driver visibility). Less considered, however, is to what degree indiscriminate lighting is used to extend “safe” limits of risk-based activity. In other words, if streets lacked lighting, would transportation engineers recommend reduced speed limits?
A prescriptive approach can set the pace for regulating permitted types of lighting, their frequency, and intensity of illumination. It can enforce compliance on properly installed lighting, such as allowing luminaires to only shine downward. A prescriptive approach begins by adopting a set of desired goals on luminosity reduction — for example, phasing out undesired types of lighting with a planned obsolescence strategy for existing stock. In terms of scope, boundaries for a site could encompass an entire territory — municipality, ward, or designated “dark preserve” sites (set aside for the conservation and preservation of light-vulnerable nocturnal habitats) — inside which quantitative and qualitative monitoring and enforcement can be managed. If desired, this same partitioning can also be used for a kind illumination zoning.
Tucson, Arizona, was an early adopter of this prescriptive approach, motivated in large part by political pressure from Kitt Peak, a nearby observatory located outside its city limits (Bazell 1971, 461). The telescope observatory, one of the largest in the U.S., was built long before the city’s rapid suburban expansion had begun to impede on the quality of sky conditions needed for field research. The city’s eventual adoption of its Outdoor Lighting Code, passed over two decades after initial complaints by astronomers, enforced limitations on times of day, types of lighting, minimum luminaire shielding requirements, geographic lighting zones, and extents of outdoor illumination permitted (Tucson 1993). Its enforcement instruments include statutory fining on a per-incident basis and, where necessary, court orders for permanently reducing or removing any lighting found in violation of the ordinance.
A restrictive approach, meanwhile, can enable a provincial or national government with regulatory instruments to allow, prohibit, or apply usage/recovery fees on products made available within its jurisdiction. For instance, a carrot-stick approach could assist with the phaseout of lighting products which fail compliance under new criteria set by administrators. Introducing an “amnesty” promotion for consumers to exchange older lighting units with designated “night-friendly” models could help facilitate this transition. In addition, compliance can be coaxed with the carrot of grants (for public infrastructure retrofit projects) or tax rebates (for private consumers) — all tools to incentivize replacing older, prohibited units with compliant products.
The “stick”, meanwhile, could include prohibitive, point-of-sale recovery fees to bulb replacement products for non-compliant lighting fixtures (e.g., all gas discharge lights). These products could still be used under a grandfather clause, but their continued operation would make them far less attractive options to newer, compliant lighting products. As well, private sector entities might also consider employing restrictive frameworks to effect compliant lighting goals. These might mimic the incentive programmes similar to Leader in Energy and Environmental Design — or LEED — awards. Alternately, a not-for-profit approach might create a voluntary guidance initiative similar to Toronto’s Fatal Light Awareness Program (FLAP), encouraging owners and operators of telecom towers and other outdoor disruptive lighting products to voluntarily find ecologically safer illumination solutions at the public relations benefit of being recognized as a friend of the organization (Gauthreaux and Belser 2006, 86).
In short, the restrictive policy approach regulates the distribution and consumption of products, thereby nudging manufacturers to meet the new demands, while the prescriptive policy approach can help promulgate enforcement of which lighting products are permitted (and how they can be used) at the local level.
Cost benefit considerations
Evaluating the best available lighting systems on the market — using long-term, service life cost-benefit assessments — can help to identify which lighting schemes will provide improved returns on capital investment costs and life-cycle operational savings. For example, if an integrated lighting system is more costly at the time of installation but projected to operate more efficiently and/or steadily for a much longer duration than the system it replaced (with lesser likelihood for premature luminaire failure), then these considerations can rationalize a marginally higher initial investment.
Cost benefit also means acknowledging the value of public/private illumination boundaries: illumination provided by a public entity should only illuminate publicly owned spaces such as streets and adjacent sidewalks and avoid shining onto private property; this leaves private lighting decisions up to the home owner. When a city plan retrofits for its streetlight luminaires, FCO luminaire designs can be used to provide even illumination across public space while sparing private property. The benefit of this approach may help to command small premium from home buyers wanting to be spared the nuisance of a nearby streetlight shining into bedroom windows.
Administratively, municipalities and regional governments must contemplate how to remediate their aggregate light footprints — that is, the telltale signature of reflective and incident outdoor lighting at night as observed from a very high altitude [Figure 2]. Facilitating this remediation means holistically looking to the challenges which could potentially complicate light pollution mitigation.
Straightforward approaches, while potentially effective across much of a jurisdiction, may still run into local situations resisting a one-size-fits-all mould. Historic districts, for example, might demand innovative remediation alternatives to replace glare-intensive luminaires (such as the classic “globe”, “teardrop”, or lantern designs known to be main sources of light trespass, ineffective illumination, and skyglow). To solve these localized challenges, it will require the direct participatory involvement of local citizens working in partnership with, amongst others, illumination planners, environmental scientists, transportation engineers, councillors, and landscape architects; ultimately, aesthetic decisions would remain vested with the citizens (Arnstein 1969, 221–2). This co-operation is essential. Questions should be encouraged, but so should demonstrative explanations highlighting why this poorly-designed designs must be phased out.
Terms of reference
A first step is to define a terms of reference for which objectives should be achieved through policy. For example: what language should a city council or legislative body consider when drafting effective by-law on light-at-night remediation or mitigation? Which guidelines should be consulted for quantitatively and qualitatively gauging targeted reduction goals — that of a not-for-profit body such as the International Dark-Sky Association, that of a professional association such as the IESNA, a consortium of scholars, or some hybrid of these?
What objectives and priorities should new policy or by-law hope to remedy, relieve, or improve? Is it only to lower long-term operational costs for lighting infrastructure? Is it to improve the quality of light at the pedestrian level without impairing visibility? Is it to prevent intrusive stray light and enact regulatory prohibitions on light trespass — that is, “the unwelcome spilling of light beyond the boundaries of the premises within which it is emitted” — for both public and private spaces (Mizon 2002, 46)? What local indigenous species are most vulnerable to lighting at night? Are there other policy frameworks in use elsewhere that could serve as templates for the drafting of new by-law language? Should sales of outdoor security lighting be regulated at a provincial, state, or national level to permit only certain features, to cap total luminosity, or to promote lighting products that use only the most energy efficient technologies on the market? Should a policy framework on lighting become part of a broader turnkey sustainability or planning initiative?
To successfully raise and inform public awareness, one of the toughest challenges is changing general perceptions of traditional lighting approaches — in effect, overcoming the resistance (or fear) of change. It is necessary to underscore how dimmer, but even illumination is as safe, if not safer for both pedestrians and drivers than adverse illumination conditions traditionally ascribed to traditional gas discharge lighting. A “more is better” tack will not work if the excess cannot be used to genuinely improve overall conditions. It is akin to using too much laundry detergent when less actually washes clothes better.
Altering this frame of mind can be difficult. This is the challenge faced by dark-sky advocates in the astronomical community (Mizon 2002, 81). This means demonstrating the fundamental, even fatal flaws behind why NCO luminaires, gas discharge lights, over-illumination, and use of “historic” or “heritage” luminaires are not only energy inefficient, but also fall short of their illumination mandate by negatively altering the quality of life for nearby residents and for nocturnal habitats. It is good to convey how important it is to illuminate only that which must be lighted, to do so evenly, and to eliminate all light shining anywhere other than where it is supposed to.
Also, illumination requirements for ageing eyes, particularly as baby boomers mature to retirement, add another layer of urgency to policymaking for outdoor lighting infrastructure. Over-lighting is problematic in of itself regardless of one’s age or vision capabilities, since transitions from excessively bright “hot spots” that emit glare to darker gaps force the eyes to constantly readjust to conditions that typically take several minutes for optimum vision recovery; these transitions are responsible for causing brief night blindness in dark zones (Pacific Gas & Electric 2008, ES-1). Ageing additively compounds these limits as the cornea and lens start losing their transparency and light is increasingly refracted around the eye before reaching the retina — creating an increased sense of glare (Goodman 2009, 233). In practice, this presents another hazard for driving at night, as well as being able to see effectively in harsher lighting conditions (i.e., inclement weather). Poorly designed streetlight luminaires only amplify vision difficulty the older one’s eyes become (Bullough, Brons, and Rea 2008, 225).
While the technical jargon explaining how vision works might not be useful for general audiences to absorb, it can nevertheless help to illustrate its basic concepts by using familiar ideas: a deer being blinded by headlights or “going blind” when bright lights are switched on inside a darkened room are good reference points. Likewise, using demonstrations to highlight the importance of better lighting and lighting policy means showing how the eyes need not adjust so dramatically to be able to see effectively in low light. In turn, this can help people recognize how detecting unusual activity after dark can be done without harsh light; to see more effectively into the scotopic range of vision beyond where the streetlight’s FCO illumination stops; how seeing best in darkness involves both rods and cones; and to describe how easily rods can be overwhelmed and eyes fatigued by glare conditions.
Whether props or multimedia are used, adding a premium to showing over merely telling can effectively reach a much wider audience as demonstrations are better able to convey complex concepts with minimal explanation.
Artificial light at night is — deliberately or unintentionally — an act of encroachment. It is encroachment upon a nocturnal ecosystem. We are not a nocturnal species. So to reify a nocturnal ecosystem, as a space separate and distinct from a diurnal ecosystem with which we are most familiar, is a new idea. Generally, ecosystems are a function of geography. Geography is tangible. The nocturnal ecosystem is less concerned with this tangibility and more with the intangible function of time. We do not travel to it so much as wait for it to arrive. When it does, our geography is unchanged, but the terms and conditions are changed. Our vision weakens. Certain activities must be suspended. The body must properly rest and regenerate itself. To do this, it needs darkness.
Our clever use of technology lets us wedge out usable pathways to make sense of this unfamiliar territory — not with a machete or with an earthmover, but by using light. The nocturnal ecosystem has very little experience with our industrial capabilities and is now taking a substantial hit from it. I do not make a case for a return to night as it was known before about 1800. This is not likely to happen. Rather, I make a case that an improved co-existence is possible and necessary. This is well within reach of our technical means and manageable using our existing policy and financial instruments.
A proposal to create an illumination planning approach is really an attempt to acknowledge the cross-disciplined nature of this challenge that we as a species generated for ourselves. We have learnt to use light indiscriminately. We must now learn how to use light prudently, to understand it fully, to begin to trust our senses after dark, and to provide stewardship in whatever way practical to help undo our light-triggered biological harm.
Our collective knowledge is tucked away in different places, but without interdisciplinary emphasis, they are as only as effective as ships passing in the night. This paper includes the foundation for an illumination planning approach as an invitation for these disciplines to work with one another instead of in each other’s absence. To name illumination planning is to give it a place where the diverse participation of disciplines and stakeholders can come together to understand a complex problem.
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