Excerpts from Light Pollution Handbook
Excerpts from Light Pollution Handbook
Target audience: “those responsible for design, installation, and maintenance of outdoor lighting installations” and public spaces.
“Emphasis on light pollution that interferes with astronomical observations.”
“an engineering approach…practical and economic solutions for problems stated in science terms.”
Ch.1-7 General interest and recommendations for decision makers, especially for public space.
Ch. 8+ is “science and engineering elaboration” for managers, designers, installers.
Not in book: light scatter in atmosphere; technological details of lighting design; legislation and regulations
1 Avoid the light, or reduce the disturbance
6 Regarding philosophy of night: “The conservation of the starry night is essential for the development of human consciousness.”
11 Not a rant—recognizes “the unambiguous positive effects of high-quality outdoor lighting.
12 See bullet items—a long haul approach.
16 Energy chain illustrates how only about 1% of initial energy makes it from generator to roadway reflection.
53 The 168 hour economy
61 Practical minimum of the natural background radiation is ~21.6 magnitude per square arcsecond (3.52 x 10-4 cd/m2). [SQM]
66 “If humanity loses contact with the cosmos, it may lose contact with some of its most profound spiritual fundaments.”
68 Yarger Observatory an ALCoR 1 facility (p.71) and an E2 district (p. 71) [AstroCamp]
69 Refutes widely cited data, such as price tag of wasted light—or at least acknowledges some of the so-called “wasted” energy is unavoidable: “calculations over-estimate energy loss,” with particular reference to Crawford’s estimate of “loss.”
69+ Connects light pollution to air pollution—combat both.
71 Distant visible luminaries, though glare, do not impinge on astronomical observatories—tis purely aesthetic (see 9.1.7d)
Specific recommendations (excerpts and quotes) for L.P. advocates,
including “custom-made solutions” (p. 87) from
93 Influence of light (on plants) is well known, but not influence of light pollution (on plants);
CAVEAT: many authors base their work on the same few sources.
95 Insects sensitive toward blue light; hence, mercury vapor are band and high pressure sodium good; non-cutoff lights attract 12 times as many insects as cutoff, per one story (good for predators, though)
107 “The main subject of this book—the restriction of light pollution,” yet it delves into…addiction
118 “The number of measurements and their quality, however, seems rather meager in view of the importance to restrict light pollution for optical astronomy.”
“It would be better if one could use the actual, direct measurements of
the ‘light distribution’ of cities or of other large outdoor lighting
installations…a matter that deserves further attention.”
[PLATO: See opening paragraph on p. 131 re: need for study]
Use most efficient source, low pressure sodium, where amenity and crime
considerations are not a factor for traffic lighting; color rending is not
important (however, see p. 208, 1); [Gumwood]
196 After seemingly erroneous calculations are given: “We give it here only to be aware of experts!” Similarly, “references given are not exactly right” (p.226).
253 The IAU suggestion to restrict artificial airglow stray light to not more than 10% of the natural background is more stringent than necessary. Authors suggest there is room to give.
254 “Observers will ‘see’ what they expect.”
255 “The role of expectancy;” we expect a silvery full moon, but compared to a wall illuminated by the setting sun, the moon is dark grey.
262 “When a theory is adopted by the scientific establishment, all data are squeezed into it.”
271 Visual acuity depends on color of light and color of light was important aspect of road lighting.
Visual acuity decreases as light source approaches a continuous spectrum (LPS→Incandescent).
272 Less of a controversy now about color but of interest regarding L.P.
273+ Try Pulfrich-pendulum effect with double stars.
274 Visual persistence varies with color.
277 Role of a light’s flicker effect in determining distance between lights, and nee for “continuous line lighting.”
281 Resolution of the small pupil is ~1 degree at 542.5 nm (green-yellow) [Transit of Venus]
288 Conversion table and light source characteristics; power (W), luminous flux (lumen), intensity (cd).
290 “Luminaires with the strictest possible cut-ff will still be quite conspicuous…for the visual system is so sensitive.” However, visibility does not imply a detrimental effect—the ugliness is less “light pollution” and more “horizon pollution,” akin to high rises and power lines on the horizon. Hence, since not affecting observations, horizon pollution is strictly and aesthetic effect.
293 History lessons, e.g., Hipparchus classification; “traditional” limiting magnitude for stars is 6.0, taken from Almagest.
294 Explains why color of stars is hard to discern.
Glare: absolute/blinding; disability; discomfort.
Disability glare or “physiological glare”… “field of view
contains strong light” in the direction of the object viewed.
“The light from the glare source is scattered within the ocular media
when it strikes the eye. It causes a
light veil that seems to stretch over the complete field of view.”
297 If object and glare source are both seen outside fovea, axial symmetry does not apply.”
298 Two routes: 1. environmentalist—reduce glare at the source, making the installation less glaring; 2. industry—“if contrasts become smaller by glare, increase the adaptation luminance so that the threshold contrasts are lower” (industry doesn’t have to adjust lighting equipment; can sell more equipment to get increased luminance). Authors suggest tide has turned to environmentalist favor.
299 “Eye media become turbid with increasing age; glare increases with age because of steep increase of cataract with age.”
301 (In theory) to counteract disability glare, increase the contrast just as much as the contrast is decreased by the glare. (In theory) a loss of contrast can be compensated by an increase in adaptation level.
307 In conclusion, full cutoff road lighting installation…reduces light pollution and disability glare and “would require much less additional road surface luminance as compared to normal cutoff or semi-cutoff.” --yields “considerable economic advantage.”
308 Discomfort glare is psychological—it disturbs, but it does not cause decrease in visual performance.
309 Can have high discomfort glare with low disability glare, or high disability glare with low discomfort glare. Thus, reducing discomfort glare in poorly lit street may increase hazard, especially for pedestrians.
312 Discomfort glare is measured by an ordinal scale, where a number is given to the “glare experience.” Can’t distinguish difference between levels—they just exist without mathematical actions.
313 Minimal studies on discomfort glare and aging (though see disability glare and aging).
314 “One may accustomed to discomfort glare, but never to disability glare.”
Discomfort glare exists, but can be considered in design; however, its
lack of fixed, numerical criteria makes it too hard to quantify.
“Only then, while taking the non-rational considerations of the human
spirit into account, do we have a chance to be clear about what really goes on,
when people are bothered by light pollution.”
329 “Not all things said by The Masters make sense.” J
331 Describes science, a view about “the nature of natural science…”
332 In dissing claims of an “ultimate” theory, author hopes it’s at least sufficient enough to solve most practical physical and engineering problems.
332+ Phenomenology—Think whatever. The truth is that outer world which is perceived by senses. And even then you’re lucky. “Sensory processes are fraught with errors and therefore the results of sensory perceptions must be treated with the greatest care.”
333 Tutorial on models.
“Models are not ‘correct’ or ‘wrong’…Clever models work, dumb
336+ A four-level model of consciousness.
346 In detail they “study the role of human instinctive behavior on aggression: for its role in street violence and the subsequent need for road lighting.
355 Disses studies “by researchers who have no preceding knowledge about psychology,” who lump all criminals and tally all crimes.
373 Ch. 10 continues at length: intuition, conscience, “ratio”
374 Ten Commandments cited
379 “discussed in considerable detail the structure and function of the human consciousness…(for) human activities are the outcome of a decision making process.”
391 Human visual system can perform 2-3 fixations per second and detect 3-6 objects per fixation…; each sequence of two or more scenes in 3 seconds has o more than 18-54 visual elements—not all are critical.
394 “Vehicle lighting is not sufficient for the detection of all visually critical elements.” The reach of the low beam head lamps are not sufficient to provide ample lighting” when considering highway speeds, preview (reaction) times, and beam reach. “Driving at those speeds requires additional information, like overhead road lighting…:
398 While a formula may
set up “warrants” for road safety measures, “some of the ‘functions’
defined…cannot be quantified…leaves room for ‘gut feelings’ and
404 Risk homeostasis (improve the safety, countered by higher risk-taking)—not tested seriously. This book will only treat the positive net effect.
415 The values listed for the required foresight (for stationary objects, for overtaking and for emergency maneuvers), are typically very much too short. Much information cited is dangerously misleading.
temperature has little influence on lamp efficiency
sodium—nearly pure monochromatic light (therefore, suitable for outdoor and
442 LEDs—instead of a
few thousand hours, a life of 1-200,00 hours (11-23 years);
445 Compared to indoor lighting, with outdoor “the contrast of the luminance, or the brightness between the lit and unlit surfaces, is much stronger…particularly with low lighting levels.”
446 “Emphasized that any unscientific attempt intending to eliminate the light pollution without proper technical knowledge or engineering experience, may lead to unexpected adverse results or sometimes serious economic loss.”
447 “Most common
surfaces in the outdoors have a reflection factor less than about 25%.”
Emphasis on concrete.
449 Maintenance factor: ration between lowest light levels (when dirty, old) and those at the installation or replacement/cleaning.
450 “By using a dimming installation, over-lighting can be avoided, while still a long group replacement [change-them-all-at-once] can be selected.”
452 A town’s systematic street lighting “should not leave any short stretch poorly lit” for it aids the dark-adapted criminal. [Note: The preceding page of criminal scenarios and conclusions is one area where the authors have not backed up their assertions with abundant references.]
452 Authors continually correlate street lighting with crime prevention.
462 Efficiency—ratio of energy converted to visible radiation to the total energy consumed (%)
463 Efficacy—ratio of
luminous flux in lumens (lm) to total energy in watts (W), or lm/W;
466+ Begins list of features—pros and cons—of lamp types.
476 Luminaires “breath” in moisture and dust, thus degrading over time.
476+ Function of ballast—acts as impedance; transformer; stabilizer; frequency converter for gas discharge lamps.
479 “Optical controls for a large-sized lamp is not efficient in comparison with that for a small lamp.”
482 “Many globe lights
have an ULR of over 50%!”
483 Now “vintage” luminaries have tow bulbs—one 8 watt compact fluorescent for appearance and one hidden that provides the needed illumination
486 “…The cover glass not being exactly horizontal is one of the major contributing factors of the light pollution.” (large scale installations)
493 High mast installations produce low light pollution…
494 “High mast solution results in far less light pollution.”
500 “…Even the modern discharge lamps have electric efficiency, excluding the energy loss of the ballast is only about 3 times that of incandescent lamps, despite the fact that the luminous flux, in lumens, generated by the modern high-pressure lamps is about 8 times that of an incandescent lamp of the same wattage…” because “the sensitivity of human retina depends on wavelength of incoming radiation.” (Sensitivity to high pressure is greater than incandescent.)
Luminous flux is measured with a device with a spectral sensitivity corresponding to that of the eye for visible radiation.
501 “The real amount of the electric energy required for the operation of a discharge lamp is the sum of the energy consumed by the ballast, dimming device and the lamp itself.” In many cases, the consumption of electric energy by the ballast and by dimming devices is given in the separate parts of the product catalogues of lamp manufacturers.
502 The OLOR does not indicate energy efficiency.
503 Upward Light Ratio (ULR)—the proportion of the output luminous flux…of a luminaire and/or an installation emitted at or above the horizon, when luminaries are mounted in their installed position. (This is the practical value, unlike the ULOR of standard test conditions.) “ULR can only be assessed by measurements in the field.”
505 The utilization factor (the proportion of the lamp luminous flux that reaches the area to be lit) is one of the most important parameters concerning the efficiency of any lighting installation.
507 Surprisingly, to me,
“CIE-based designs are always based on the requirements of the ‘user’ of
the installation…Aspects of light pollution are not taken into account.”
509 The determination of the average road surface luminance is the cornerstone of the road lighting design. The traditional method does not include other parameters as well, more in particular the restriction of disability glare and the non-uniformity of the luminance pattern.”
“However, visual guidance, followed by the non-uniformity are the most important design parameters. There are, however, no lighting design methods, based on the driving task concepts.”
510 “Illuminance-based design is still the only practical design method…for roundabouts.” Gumwood]
512 “Road lighting is purely functional. This means road lighting must never be considered as a luxury, nor as an aesthetic feature, like many outdoor lighting systems…when dealing with city beautification.”
513 (Outline of the steps for road lighting with specific examples and criteria and parameters.)
524 New approach to road lighting based on (author) Narisada’s research; “minimize the waste on the luminous flux and on the electric energy for road lighting, while keeping or improving the visibility conditions.”
525 Problem with present
CEI system: “To maintain the relevant lighting parameter in a (CEI)
recommended range, the designers have, in most cases, to select a lamp whose
luminous flux is greater than the calculated value.”
That is, they ramp up light to cover all bases (and their rears).
539 Three factors “have a remarkable influence on the Area Ratio or the potential visibility: 1. the average road surface luminance, 2. the luminaire arrangements, 3. the mounting height…The spacing-to-height ratio when smaller than 3.5 as well as the overall uniformity have a minor influence.”
Recommended criteria: the percentage of the Area Ratio for different categories of road.
548 Paragraphs note extensive research done regarding the relation between lighting and crime and lighting and accidents. However, it is tinted by the commercial interests of the research parties and in the reporting. Severe methodological flaws are so severe it’s difficult to estimate the significance of such studies. Two parties at fault: astronomical community and the lighting and energy communities. Landmark (oft quoted) or seminal studies are themselves flawed.
550 “The solution (to
the controversy) is, of course, to do better research…”
553 “The samples we may get when studying road lighting are usually not big enough.”
554 Statistical analysis gives correlations, not causal relations (regarding accidents).
People who are not accustomed to think in terms of psychology…dump all crimes and all criminals in a heap, a major source of error. For some, light is a deterrent; for others it’s not.”
558 “Lesson to be learned…It is much more effective to stress that there are many technical and organizational ways to reduce light pollution…One reason is that…pollution restrictions offer many possibilities for technical innovation and commercial development.”
562+ Applying the meta-analysis
approach, in which material (studies) is scored with a ‘figure of merit’ and
results weighed by merit… 1.
Good road lighting reduces nighttime casualties (about 30%),
565+ Continues to question the
567 “A major problem is that almost all studies are little more than opinions and anecdotes: systematic, well designed quantitative research is almost completely lacking. It is therefore difficult to justify on a cost/effectiveness basis the expenditure for crime prevention lighting.”
568 Tien et all (1977) study, oft quoted as suggesting lighting is not an effective crime countermeasure, is not a sound conclusion. “Tien had negative effect on the motivation to do any further research.”
570 Most research was “before-and-after” type. Better alternative is relation studies. [PLATO]
573 There is a danger of circular reasoning…the thing one looks for in the results are just the things one has introduced in the data collection.” One way out is never to try to confirm a hypothesis, only to falsify it.
576 “Often, improving road lighting helps to prevent crime and to reduce crime rates. More important still, almost always an improvement in the psychological aspects were reported.”
577 “Results, however, are somewhat ambiguous.”
610 City beautification …makes life enjoyable and not just liveable. It is not a luxury, however. Human creativity, human dignity requires a set of conditions that are more than just the necessities.
611 Crime studies made
it clear that good lighting improves the atmosphere and reduces crime,
vandalism, etc. (Painer, 199,
614 Cutoff—or coupure—of vehicle headlights
622 HID-lamps have higher efficacy (up to 85 lm/W) than halogen (20-25 lm/W); (halogen are essentially tungsten filaments)
623 Per study, “For
the same luminous intensity, high pressure gas discharge (HID) lamps caused a
higher degree of discomfort, as compared to sealed beam lamps.
Furthermore, the discomfort in the field test was greater than predicted
from laboratory tests.”
626 “Total luminous flux emitted by HID lamps is so high that polarized light may become a workable proposition.”
628 It would benefit road safety, but not reduce light pollution.
629 “Most countries
are stuck with headlighting systems that do not fit their national or regional
characteristics at all.”
633 Collisions with
loose objects on or near the road represent less than 1% of the total injury
accidents, yet these objects represent the ‘standard object’ of road tests.
634 Disability glare, “the outstanding problem in nighttime road traffic…increased very clearly with each step in the further development of vehicle headlighting systems.”
635 All of these headlight regulations are “based on ‘type testing’…that depends on the test result of small sample, that sometimes consists of only one item. Obviously, this almost invites the provider to select the best possible item for the test.” For some regulations, “the provider must declare that the complete production is in agreement with the test items.”
636 “Formally, headlighting systems are vehicle parts, and not parts of a vehicle. Thus, they are tested separately…and fall outside the regulations.”
640 Light pollution contributed by headlights is significant, particularly in sparsely populated areas.
646 Begins tutorial on cost-benefit ratio analysis
652 Concludes that “increasing the light level on urban roads is a cost-effective accident reduction measure.”
658 Specular reflectors, or mirrors, are used most frequently. Aluminum (high reflectivity) is vulnerable, because weak, so it requires frame to hold its shape. However, this allows them to be bent purposely for better light control (especially suitable for metal halide and HPS lamps and for “high class lighting installations,” like stadiums and squares). Too complicated for ordinary road use.
Anodized aluminum luminaries must be enclosed with transparent cover.
659 Stainless steel reflection is low; heats up; “not easily ‘workable’”; but sturdy housing holds shape, so can be open with no cover. Housing serves as reflector.
662 Illuminance of open luminaries would be significantly higher over 6 years than that of a low-quality closed luminaire.
666 For optimal adjustment, one needs clear, transparent cover, not refractor luminaire.
668 Regarding the “flat glass controversy…any shape other than flat glass will result in some light emitted upwards, directly from the luminaire.”
668 Regarding misunderstanding that direct light exceeds reflected light: “Concentrated light sources, like street lighting luminaries, are highly conspicuous to the dark adapted eye, even if their actual luminous intensity is modest.”
673+ Compares luminaries with different cover shapes. Notably, flat glass consumes 34% more energy than most efficient one in study.
677 “The difference between different cover shapes is marginal.” As expected, flat-glass covers perform slightly higher and the upward flux is slightly lower, and the “reach” is slightly lower. “These differences can be neglected in practice.”
678 With different cover shapes, “there may be considerable differences as regards the split-up between the direct and the indirect—or reflected—component of the upward flux…The shape of the cover of the luminaire has some influence on the performance of the installation, as well as on the total upward flux, but statements that have some general validity cannot be made.”
720 In the
(From p. 742...) Though only a small fraction of the total energy consumption, “the amounts are staggering when looked at in absolute terms.”
Includes conversion tables
755+ “Visual conditions under which cones are active [bright] are called the conditions of photopic vision.” Rods [dark] are scotopic vision. Between is mesopic vision.
757 1 Watt=683 lumens
Luminous flux is the “energy flux weighted according to the spectral luminous efficiency curve for the human photopic visual system.” This amount of light is in units of watts; accumulated amount is exposure, the product of illuminance and time.
[Note: major sections of Ch. 14 are skipped here.]
852 “Photometry is a specialized profession, that requires skill, good equipment, and a very large dose of experience. There are many things that can go wrong; there are many pitfalls.” [PLATO]
859 “The level of the
sky glow, even at the same location, is not a constant in time:
360 Area Surveys
881 Eloquent paragraphs regarding astronomy as an endangered science, based on paper by Paul Murdin.
882 “A major goal of this book…is to create mutual respect between the two professions…” of astronomers and lighting engineers.
884 Per Sperling, “Astronomers most often succeed when they exercise personal connections with government officials—a very depressing conclusion for societies so proud of their democracies.” Hence, “political pressure not the best means to find any long term improvement in the light pollution situation.” Instead→education/outreach.
886 Reward desirable behavior as opposed to punishing undesirable behavior.
887 Dearly missed are simple short primers on the subjects of astronomy, outdoor lighting, and light pollution…Need to have a standard high enough for secondary schools, for college level courses, for astronomers, engineers, and public decision makers.”
893 From Isobe et al
(2000), DMSP-satellite data indicates energy emitted upward (in kWh/km2),
which can be compared to preceding years.
897 “It is often felt that a lack of awareness, rather than specific resistance, is generally the biggest problem in controlling light pollution.”
899 A Light Pollution Act should embrace the concept of annoyance, as opposed to nuisance.
912 Scheme for local lighting ordinance.
Copyright ©2009 Chuck Bueter. All rights reserved.