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International Journal of
Environmental Research
and Public Health
Hypothesis
Urban Lighting Research Transdisciplinary Framework—A
Collaborative Process with Lighting Professionals
Catherine Pérez Vega 1,2,3 , Karolina M. Zielinska-Dabkowska 3,4 ,* and Franz Hölker 1,2
Citation: Pérez Vega, C.;
Zielinska-Dabkowska, K.M.; Hölker,
F. Urban Lighting Research
Transdisciplinary Framework—A
Collaborative Process with Lighting
Professionals. Int. J. Environ. Res.
Public Health 2021,18, 624.
https://doi.org/10.3390/ijerph
18020624
Received: 2 December 2020
Accepted: 8 January 2021
Published: 13 January 2021
Publisher’s Note: MDPI stays neu-
tral with regard to jurisdictional clai-
ms in published maps and institutio-
nal affiliations.
Copyright: © 2021 by the authors. Li-
censee MDPI, Basel, Switzerland.
This article is an open access article
distributed under the terms and con-
ditions of the Creative Commons At-
tribution (CC BY) license (https://
creativecommons.org/licenses/by/
4.0/).
1Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Müggelseedamm 310, 12587 Berlin, Germany;
perez.vega@igb-berlin.de (C.P.V.); hoelker@igb-berlin.de (F.H.)
2Department of Biology, Chemistry, and Pharmacy, Institute of Biology, Freie Universität Berlin,
14195 Berlin, Germany
3
Faculty of Architecture and Design, Hochschule Wismar University of Applied Sciences Technology, Business
and Design, 23966 Wismar, Germany
4GUT Light Lab, Faculty of Architecture, Gdansk University of Technology (GUT), 80-233 Gdansk, Poland
*Correspondence: k.zielinska-dabkowska@pg.edu.pl
Abstract:
Over the past decades, lighting professionals have influenced the experience of the night
by brightly illuminating streets, buildings, skylines, and landscapes 24/7. When this became the
accepted norm, a dual perspective on night-time was shaped and the visual enjoyment of visitors after
dusk was prioritized over natural nightscapes (nocturnal landscapes). During this time, researchers
of artificial light at night (ALAN) observed and reported a gradual increase in unnatural brightness
and a shift in color of the night-time environment. As a consequence, ALAN has been identified
as a relevant pollutant of aquatic and terrestrial habitats, and an environmental stressor, which
may adversely affect a wide range of organisms, from micro-organisms to humans. Unfortunately,
lighting professionals and ALAN researchers usually attempt to solve today’s sustainable urban
lighting problems distinctive to their fields of study, without a dialogue between research and
practice. Therefore, in order to translate research knowledge as an applicable solution for the lighting
practice and to minimize the impact on the environment, a collaborative framework involving
a transdisciplinary process with lighting professionals is crucial to potentially bring the practice,
research, production, decision-making, and planning closer to each other. This paper presents a
framework to help reduce the existing gap of knowledge, because appropriate lighting applications
depend upon it. Access to less light polluted nightscapes in urban environments is just as important
as access to unpolluted water, food, and air. This call for action towards sustainable urban lighting
should be included in future lighting policies to solve the urgent environmental and health challenges
facing our world.
Keywords:
light pollution; ecological light pollution; sustainable lighting; urban planning; lighting
professionals; ALAN researchers; urban lighting research; transdisciplinary research
1. Introduction
Today, most cities and towns have a prolific network of artificial light at night (ALAN)
that illuminates traffic and pedestrian routes, as well as buildings and landscapes, not
only for visibility but also to provide visitors and residents with visual enjoyment and
entertainment after dusk [1,2].
Over time, as the network of ALAN expanded from urban to peri-urban environments
towards rural landscapes [
3
], the globe has endured the spread of unnatural brightness
and vivid colors of light at night, which is today encroaching into new territories that were
previously unlit [4].
Over the past two decades, night-time studies have reported evidence on the pres-
ence of ALAN as an unintended form of anthropogenic pollution, known as light pollu-
tion (LP) [
5
,
6
] and ecological light pollution (ELP) [
7
] which has significantly increased
Int. J. Environ. Res. Public Health 2021,18, 624. https://doi.org/10.3390/ijerph18020624 https://www.mdpi.com/journal/ijerph
Int. J. Environ. Res. Public Health 2021,18, 624 2 of 18
over the years [
4
,
8
,
9
]. It has been described as the inappropriate application and man-
agement of artificial light sources and luminaires cohered to the rapid development of
urbanization, which leads to the unnecessary and undesired emissions of ALAN across
landscapes [
10
,
11
]. The latest research on the environmental impact of ALAN indicates that
night-time environments in aquatic and terrestrial ecosystems are increasingly impacted
by light pollution [
12
–
15
]. ALAN has become a stressor of natural cycles and biological
processes that potentially threatens biodiversity [
16
–
19
], and biological rhythms in humans
and nature [
20
–
24
]. Moreover, an induced suppression of melatonin, the night hormone,
has been reported in various vertebrate species [
25
] even when exposed to comparative
low skyglow light levels. Although the lighting practice has gained awareness of the
concept of light pollution, [
26
,
27
] as the result of incorrectly managed properties of artificial
lighting, the challenge remains to translate research notions beyond the known concept
of light as a pollutant to the actual planning and design of lighting schemes that provide
appropriate illuminance levels for visibility, whilst also protecting the natural night-time
environment [11,28–31].
2. Challenges for the Practice
Practical solutions to address the rapid rise of ALAN and minimize its adverse effects
have become challenging and complicated to implement due to various reasons.
2.1. Reasons to Consider
Firstly, the prompt development of urbanization encouraged the planning, designing,
and application of technical lighting parameters that centered on users [
32
]. These solutions
corresponded to photopic vision during the day [
33
], which is the visual sensitivity and
ability to see when exposed to bright environments [
34
]. Eventually, the simulation of
daylight conditions for night-time environments was implemented as a means to translate
a sense of visual understanding across night-time landscapes. The lighting practice recog-
nized the application of artificial lighting as a way to provide safe passage for pedestrians
and to allow vehicles to circulate at night [
35
,
36
], but environmental concerns were usually
ignored. This use of artificial lighting soon became an environmental concern because
luminaires were continuously operated from dusk to dawn, which impaired circadian
rhythms (set by location-specific natural day and night cycles). It also created a continuous
period of brightness with unnatural colors of light at night, emitted from artificial lighting
across landscapes.
Secondly, potential environmental problems related to, for example, biodiversity
and the protection of natural nightscapes have rarely been discussed in the lighting
practice [
37
–
39
]. This is mostly owing to the fact that to understand the impact of ar-
tificial lighting technologies on biodiversity, at least a basic disciplinary knowledge of
ecology is required.
Thirdly, in recent years, the lighting industry and its practice continues to promote the
replacement of conventional lighting technologies (e.g., high- and low-pressure sodium—
LPS and HPS) to solid-state lighting applications (with the focus on light-emitting diodes—
LEDs). LEDs are considered a “sustainable lighting solution” that delivers higher efficacy
at a lower cost. However, saving energy costs does not solve the problem of increased
emissions of light at night (rebound effects, e.g., [
4
,
40
]) or luminaires that direct undesired
and unnecessary light upwards, without considering the impact of downward emissions to-
wards aquatic and terrestrial environments, whilst also operating luminaires continuously
from dusk to dawn.
Lastly, in regards to the temporal and spatial emission patterns of ALAN, the cur-
rent discussion about light pollution and available lighting standards and guidelines,
both focus solely on the protection of the night sky [
41
–
44
]. However, the evaluation of
obtrusive light and the approval of lighting installations as an enforced practice rarely
occurs [
26
]. Although in some countries there are existing regulatory frameworks such
as guidelines, procedures, standards and codes, or legal acts relevant for urban lighting
Int. J. Environ. Res. Public Health 2021,18, 624 3 of 18
and light pollution (Table 1), unfortunately there are no globally established design and
technical parameters available for lighting projects that aim to be respectful to ecology and
the natural environment. Most often, the lighting design process lacks an Ecological Impact
Assessment in Feasibility Study, which may vary from one country to the next [
45
,
46
].
Additionally, lighting professionals and ALAN researchers usually attempt to overcome
problems particular to their field of expertise, with insufficient dialogue across research
and practice disciplines. The vocabulary and know-how of both domains differ, as they
address issues that are specific and relevant to their field of study.
Table 1.
Examples of regulatory frameworks for urban lighting and light pollution based on [
40
,
47
,
48
] and references
therein.
Category Year Name Country of Origin
Guidelines
1997 CIE 126-1997. Guidelines for minimizing sky glow, by the International
Commission on Illumination (CIE) International
2009 Artificial Light in the Environment Report, by the Royal Commission on
Environmental Pollution UK
2017
CIE 150:2017. Guide on the Limitation of the Effects of Obtrusive Light from
Outdoor installations, 2nd Edition, by the International Commission on
Illumination (CIE)
International
2018 IDA—International Dark Sky Community Program Guideline International
2019 The Austrian Guidelines for Outdoor Lighting, by the Department of
Environmental Protection Australia
2020 GN01-20. Guidance Note 1 for the reduction of obtrusive light 2020, by the
Institution of Lighting Engineers (ILE) UK
Procedures
2002
A handbook of practical guidelines for managing street lighting to minimize
impacts on sea turtles, by the Florida Power Company, Coastal Roadway
Lighting Manual
USA
2011
Model Lighting Ordinance (MLO)—User’s Guide, by the International Dark Sky
Association (IDA) and Engineering Society of North America USA/International
2018 Dark Sky Manual for Homeowners, by the Utah State Parks USA
Standards
and Codes
1989/2011
Flagstaff Outdoor Lighting Code USA
2003/2015
EN 13201-2: Road lighting—Part 2: Performance requirements, by the European
Committee for Standardization (CEN) Europe
2014
EN 12464-2 Light and Lighting—Lighting of Work Places, Part 2: Outdoor Work
Places, by the European Committee for Standardization (CEN) Europe
2020
ANSI/IES LP-11-20 Environmental Considerations for Outdoor Lighting, by the
American National Standards Institute and Illuminating Engineering Society USA/International
Legal Acts
1958 Flagstaff Lighting Ordinance USA
2006 Section 102 of the Clean Neighbourhoods and Environment Act (2005) UK
2007 Light Pollution Law concerning street lighting, facade illumination Slovenia
2011 Public Lighting decree in Berlin Germany
2011 Decree No. 2011-831 of 12 July, 2011 on the prevention and limiting of light
pollution France
2012 Decree No. 2012-118 of 30 January, 2012 on the outdoor advertising, signs and
signposting France
2013
Order of 25 January, 2013 on the night-time lighting of non-residential buildings
in order to limit light pollution and energy consumption France
2018
Decree of 27 December, 2018 on the prevention, reduction and limitation of light
pollution France
Int. J. Environ. Res. Public Health 2021,18, 624 4 of 18
Consequently, the adoption of collaborative practices via the exchange of vocabulary,
expertise, and knowledge rarely occurs, even if both lighting practitioners and ALAN
researchers have an increasing interest in collaboration [2,49–51].
2.2. Towards Inclusive, Collaborative, and Transdisciplinary Lighting Research and Practice
In 2010, ALAN researchers had already emphasized that a transdisciplinary research
agenda can potentially favor the development of regulations and guidelines that meet
environmental needs and the demands of modern societies [
8
]. Interestingly, lighting
professionals were often not considered back then as part of the actors involved. However,
today, lighting professionals are judged to be crucial team members who can introduce
new ways of thinking about research problems. They can also provide essential research
inputs based on their practical knowledge of artificial lighting.
As the dialogue between lighting professionals and ALAN researchers remains in-
sufficient to translate the acquired data as knowledge into the practice domain, it is of
great significance to improve the application of artificial light to minimize the impact of
light pollution on the environment via a more efficient and effective collaboration between
researchers, lighting practitioners, policymakers, and society in the context of urban light-
ing. With this paper, we aim to provide a brief insight into the perspectives of the lighting
practice and research on night-time studies, we explain the actors involved in each domain,
while also offering potential platforms to exchange and transfer knowledge, and we make
a call for action on an improved transdisciplinary approach. The proposed collaboration
framework has the purpose of bringing those involved in practice, research, production
inputs, planning, and policy-making domains all closer in order to conduct and coordinate
the organizational structure in which information flows. This transdisciplinary teamwork
may serve to translate and convey research knowledge between lighting professionals and
ALAN researchers, to better provide healthier and more sustainable urban settings, which
are inclusive and protective of the night.
3. Development of the Dual Perspective of the Night
In medieval times, most cities and towns were in darkness after dusk so additional
illumination via lit candles and torches was used for wayfinding along routes [
52
]. Since
then, the practice of lighting incorporated varied approaches to deliver illuminated night-
time scenarios in built and natural environments (Figure 1).
Dark pathways were dappled with pools of artificial light in core key locations (e.g.,
pedestrian street intersections or the façades of important buildings). Areas were illu-
minated with light rich in long wavelengths with warmer correlated color temperatures
(CCT) at approximately 1800–2200 K [
52
]. The light distribution of these light sources
was also closer to the ground and restricted to areas of common passage. Night-time
illumination had not yet infiltrated terrestrial and aquatic landscapes as portrayed in the
1879 impressionist oil painting Walk with lanterns by Ilya Repin [
53
]. Skyglow was also not
considered a problem, as cities still remained relatively dark at night (Figure 1a).
Later, gas lighting technology and the emergence of electric lighting provided the
means to establish urban lighting systems with multiple fixed lanterns in poles to increase
illuminance parameters and to deliver horizontal homogeneous illumination that did not
occur in medieval times. An increased number of lanterns per fixed pole were applied
in streets, roads, and paths to enable pedestrian and vehicular circulation. The spectral
power distribution (SPD) of these point sources was considered rich in long wavelengths
with a correlated color temperature that increased from approximately 2000 up to 2700 K.
The introduction of these forms of urban artificial lighting producing low light levels were
expected to attract, for example, insects in the vicinity of the applied sources, “Wie Motten
um das Licht”—like moths around a flame, as mentioned in the song Falling in love again by
Marlene Dietrich [
54
]. Urban areas began to show the first traces of skyglow in cities and
towns (Figure 1b).
Int. J. Environ. Res. Public Health 2021,18, 624 5 of 18
Int. J. Environ. Res. Public Health 2021, 18, x 5 of 17
Figure 1. The evolution of urban illumination over time, illustrating the varied approaches of arti-
ficial lighting practice used to deliver illuminated night-time scenarios in built and natural land-
scapes. In the beginning, there were (a) relatively dark pedestrian pathways with dappled pools of
light at street intersections and soupçons of light washing the first-floor façade of important build-
ings mainly used by citizens at night. Later, (b) robust iron poles with lanterns were applied to
luster streets, roads, and paths. Then, (c) skyscrapers and tall buildings acquired illuminated ele-
ments for advertisement with vertically illuminated façades that reveal the structure of buildings.
In the following years, (d) functional and decorative lighting co-existed in the same urban realm to
make cities and towns functional and aesthetically pleasing at night. In recent years, (e) functional
lighting for pedestrian and vehicular circulation and decorative lighting for skyscrapers, build-
ings, monuments, and landmarks have presented a changing luminosity and color condition with
shifting shapes, patterns of shadow and light, along with videos projected onto buildings so they
become illuminated canvases at night. Source: authors’ own work.
Then, in addition to the horizontal illuminance parameters, artificial light was used
as a medium on the vertical surface of tall buildings and skyscrapers to sculpt volumes
for three-dimensional spaces. During the 20th century, multiple techniques emerged that
included the uplighting of building façades as well as the use of searchlights, which are
high-intensity electric sources of light used for finding objects in the distance at night.
Searchlights were positioned to direct emissions of light towards the sky [55]. Further-
more, decorative advertising lighting systems were used to illuminate the top of buildings
with marquee signs and letterings. Unfortunately, the position and direction of point
sources used to illuminate the vertical plane directed light towards the sky. They also de-
livered higher illuminance parameters when compared with lighting systems used in pre-
vious years. Such light sources were present in illuminated parks, exposing the leaves of
trees and plants to the emissions of light; as observed and reported in 1975, ALAN was
considered to affect the flowering state in varied flowering plants [56].
Additionally, the beams of floodlights on the roofs of theatres and cinemas became
iconic urban illuminated elements that were observed to attract migrating birds at night,
as shown at the Eddystone lighthouse illustrated in 1912 [57]. In comparison to previous
years, artificial lighting began to feature broad ranges of SPD from approximately 400 to
700 nm, with richness in short wavelengths of light and less red wavelengths. This was
Figure 1.
The evolution of urban illumination over time, illustrating the varied approaches of artificial
lighting practice used to deliver illuminated night-time scenarios in built and natural landscapes.
In the beginning, there were (
a
) relatively dark pedestrian pathways with dappled pools of light
at street intersections and soupçons of light washing the first-floor façade of important buildings
mainly used by citizens at night. Later, (
b
) robust iron poles with lanterns were applied to luster
streets, roads, and paths. Then, (
c
) skyscrapers and tall buildings acquired illuminated elements
for advertisement with vertically illuminated façades that reveal the structure of buildings. In
the following years, (
d
) functional and decorative lighting co-existed in the same urban realm to
make cities and towns functional and aesthetically pleasing at night. In recent years, (
e
) functional
lighting for pedestrian and vehicular circulation and decorative lighting for skyscrapers, buildings,
monuments, and landmarks have presented a changing luminosity and color condition with shifting
shapes, patterns of shadow and light, along with videos projected onto buildings so they become
illuminated canvases at night. Source: authors’ own work.
Then, in addition to the horizontal illuminance parameters, artificial light was used
as a medium on the vertical surface of tall buildings and skyscrapers to sculpt volumes
for three-dimensional spaces. During the 20th century, multiple techniques emerged that
included the uplighting of building façades as well as the use of searchlights, which are
high-intensity electric sources of light used for finding objects in the distance at night.
Searchlights were positioned to direct emissions of light towards the sky [
55
]. Furthermore,
decorative advertising lighting systems were used to illuminate the top of buildings with
marquee signs and letterings. Unfortunately, the position and direction of point sources
used to illuminate the vertical plane directed light towards the sky. They also delivered
higher illuminance parameters when compared with lighting systems used in previous
years. Such light sources were present in illuminated parks, exposing the leaves of trees and
plants to the emissions of light; as observed and reported in 1975, ALAN was considered
to affect the flowering state in varied flowering plants [56].
Additionally, the beams of floodlights on the roofs of theatres and cinemas became
iconic urban illuminated elements that were observed to attract migrating birds at night, as
shown at the Eddystone lighthouse illustrated in 1912 [
57
]. In comparison to previous years,
Int. J. Environ. Res. Public Health 2021,18, 624 6 of 18
artificial lighting began to feature broad ranges of SPD from approximately 400 to 700 nm,
with richness in short wavelengths of light and less red wavelengths. This was coupled
with an increase in the range of CCT from approximately 2000 K up to 5000 K [
58
,
59
]. The
combination of techniques and applied light sources resulted in an unintended diffused
luminous dome, visible over densely populated areas at night. This man-made effect is
called skyglow. The use of light sources with a broad SPD rich in short wavelengths has
allowed illuminated landscapes at night to appear as they would during the day. Artificial
light at night became an artificial accoutrement of nightscapes and a convincing cultural and
social excuse to construct and promote over-illuminated cities that unintentionally neglect
the loss of the night [
60
]. Population growth, the exponential increase in illumination
per capita, and the increased number of point sources and numerous applied techniques
across landscapes have all presented unforeseen consequences, reported at the end of
1980s with the first research articles on light as an anthropogenic, artificial, and detrimental
component. The aim of this research was to raise awareness about the problem in the form
of skyglow and to also help reduce light pollution from urban and rural environments [
5
,
6
]
(Figure 1c).
It soon became strategic to use new lighting techniques for the scene setting of local
historical landmarks to change the overall perception of urban built environments. At the
end of the 20th century, applied lighting techniques mainly focused on engaging the user
with the encountered space at night with higher illuminance parameters, varied correlated
color temperatures, and spectral power distributions that ranged across the visible spec-
trum, shadows, and the duality of brightness and darkness [
61
–
65
]. The upward emission
of artificial lighting coupled with higher levels of brightness has resulted in significant
light pollution across ecosystems (e.g., night-time illuminated bridges, which emit artificial
light towards aquatic ecosystems and are known to negatively affect migrating salmon
fish [
66
], and uplit trees and green areas in parks and public gardens, which may adversely
alter other organisms, such as insects [
16
,
67
]). Night-time illumination soon reached areas
that were once unlit (Figure 1d). These approaches typically defined lighting practices that
focused on the role of night-time illumination in an urban context to engage the user with
the various spaces they used at night [
68
], and the detrimental impact of artificial lighting
on humans and nature was not yet considered by lighting experts.
Meanwhile, ALAN researchers focused on gathering evidence of artificial light as
a long-term phenomenon and pollutant of night-time environments [
69
]. This includes
the founding notions and observations of the sky by night. Since the 1900s, the earliest
measurements of photon emissions produced per capital demonstrated that cities were
under an artificially bright night sky [70].
Astronomers and astrophysicists reported a noticeable reduction in the visibility of
the naturally dark sky due to an increase in illuminance and the use of unnaturally vivid
colors of light at night in densely populated areas [
71
,
72
]. Over the years, the application
of artificial lighting with upward emissions of light and higher levels of brightness resulted
in significant light pollution across landscapes.
Unfortunately, opportunities to acquire this new knowledge to understand the con-
sequences of the inappropriate use of ALAN was scarce, as the notion that ALAN is a
pollutant was still being explored by ALAN researchers.
Moreover, at the beginning of the 21st century, there was a distinct lack of knowledge
about the numerous properties of artificial lighting, which are now known to be pollutants.
There was also a lack of communication, which was needed in order to translate research
into the practice of lighting.
New technological developments enabled multiple techniques to emerge. This in-
cluded dynamic artificial lighting with changes in brightness, color temperatures, colored
light, and shadow patterns, as well as the projection of videos onto buildings so they
became illuminated canvases [
61
–
65
]. The increased application of artificial lighting came
at the expense of the natural night-time environment. ALAN researchers estimated that
there was a higher variability of artificial lighting conditions across landscapes, such as
Int. J. Environ. Res. Public Health 2021,18, 624 7 of 18
significantly increased levels of brightness [
4
,
19
] as well as the widespread use of unnatural
colors, which is considered to affect varied organisms [
14
]. Upward illumination towards
the sky, such as the 9/11 Memorial—Tribute in Light [
73
], has been reported to affect mi-
grating birds [
74
]; another example is the bat colonies in various illuminated churches
across Sweden, where bats have been observed to change their flight trajectories to avoid
illuminated areas, which can potentially affect the choice of corridors during flight and
may fragment the selection of foraging areas for bats [75] (Figure 1e).
Previously unlit areas at night were now being illuminated, (e.g., illuminated bridges
that disturb the ecology of rivers and bodies of water, as well as skyscrapers and tall
building that emit light towards the sky, which harms birdlife and insects). During recent
years, light pollution and ecological light pollution have been diligently investigated
via scientific research to broaden the understanding of the impact of night-time lighting
applications on humans and nature [7,20–22,24,25,76].
Table 2provides a description of the evolution of outdoor lighting chronologically
over time.
Table 2. The evolution of outdoor lighting. Source: authors’ own work.
Figure 1Description
(a)
During medieval times, most cities and towns were illuminated by night with point source illumination (e.g., candles
placed adjacent to windows, lanterns positioned at a determined height in façades, and hand-held lanterns. Fire (e.g.,
present in candles and hand-held lanterns) was used as a beacon of light to help shape a sense of understanding of the
urban realm after dusk.
(b)
Later, electrical engineers (EE) and illuminating engineers (IE) used gas and electrical light sources that included
incandescent, low-pressure sodium (LPS), and high-pressure sodium (HPS) as point light sources for streets, roads, and
paths to facilitate pedestrian and vehicular circulation [77]. Gas and electrical point sources of illumination were
considered static as they lacked movement compared to previously applied light sources such as carried hand-held
lanterns and gas-fueled fixtures that were frequently moved to the locations to provide visibility at night. Mounted
lanterns on poles were introduced, and in the years following, the number of lanterns per fixed pole increased.
(c)
During the 20th century, IE and architectural lighting designers (ALD) favored an ensemble of lighting systems that
vertically illuminated skyscrapers and tall buildings. Decorative advertising lighting systems also became popular. The
economic growth of the post-war years instigated the application of emerging static point light sources that included
fluorescent lamps (FL), ceramic metal-halides (CMH), and neon lamps to built environments that had formerly only
been illuminated by incandescent, LPS, and HPS. Neon lamps were used for the lettering placed on the top of buildings
to advertise brands, products, and locations, whereas incandescents were used to illuminate marquee signs and
letters [78,79].
(d)
The end of the 20th century saw the introduction of urban lighting masterplans (ULM) by IE, EE, and ALD, and urban
lighting planners (ULP) introduced ULM to revitalize the function of cityscapes and also to create a decorative
appearance of cities at night as a symbol of economic growth and to boost tourism [65]. A wide range of approaches
included functional point sources (e.g., for pedestrian and vehicular circulation), as well as decorative point sources
(e.g., for the vertical illumination of historical buildings and landmarks for advertisement).
(e)
During the early years of the 21st century, a new emerging lighting technology called light emitting diodes (LEDs)
became the preferred choice of technology by the IE, EE, ALD, ULP, and entertainment designers (EA) to illuminate
built and natural landscapes (Figure 1e). LEDs offered low cost, easy application, and miniaturization for functional
lighting for pedestrian and vehicular areas, decorative lighting for the enhancement of historical and modern buildings
(e.g., skyscrapers, buildings, monuments, and landmarks), and static and dynamic lighting characteristics (rich in
movement with changing colors and illuminance parameters) to the modern cityscape.
In the first decades of the 21st century, ALAN researchers have provided evidence
on night-time illumination as a pollutant that disrupts biological rhythms in humans and
nature [
9
,
80
,
81
] and have estimated an increase in LP of 2–6% per year [
4
,
19
]. Additionally,
environmental researchers have reported that LP and ELP inhibit crucial day and night-
time cycles across taxa, since 30% of all vertebrates and more than 60% of all invertebrates
have visual sensitivities attuned to natural low light levels, which involves the ambient
illuminance of lunar cycles and starlight in the night-time environment [
19
]. An extensive
body of empirical evidence has identified potential behavioral and physiological changes
Int. J. Environ. Res. Public Health 2021,18, 624 8 of 18
in responses induced by properties of ALAN across taxa; this includes terrestrial organisms
such as bats [
82
], birds [
83
], and insects [
16
,
84
], micro-organisms, and aquatic species
exposed to artificial lighting near waterfronts, bridges, rivers, and lakes [13,85,86].
Eventually, a dual perspective of the night was formed as both lighting professionals
and ALAN researchers developed individual outlooks focused on ALAN. This caused a
no-win/Gordian Knot situation [
87
–
89
] that challenged the research and lighting practice
due to different approaches and limitations. For the majority of the lighting practice, the
method for lighting technologies involved expertise that mainly focused on delivering the
user visual accessibility for visited areas at night, and beyond that, a sense of connection
to urban night-time environments. Meanwhile, ALAN researchers presented expertise
focused on the study of an unnatural component, such as artificial light and its properties
and the resulting adverse effects across night-time environments, and this included the
widespread use of ALAN causing skyglow: a global phenomenon responsible for the loss
of the night (e.g., [90,91]).
The actions against light pollution and the improper management of lighting ap-
plications are not necessarily a confrontation between ALAN researchers and lighting
professionals [
39
,
92
], but rather an attempt to start a transdisciplinary collaboration be-
tween experts, which includes best practice and sustainable lighting applications that
serve society’s interests while respecting ecology [
93
]. An example of a transdisciplinary
collaboration between environmental and lighting experts occurred in the city of Berlin,
Germany, in 2011. This involved a Lighting Advisory Board, which included lighting
and environmental experts in collaboration with the Senate Department for Urban Devel-
opment of the city of Berlin, to conceptualize the urban lighting masterplan for the city
of Berlin (Stadtbild Berlin–Lichtkonzept) (Senatsverwaltung für Stadtentwicklung und
Umwelt, 2011). The lighting masterplan concept portrays the city as an economic center
and provides citizens with a sense of safety and security whilst enhancing the allure of the
city with lighting technologies that minimize the impact of light upon ecology at night.
The conceptualization of a transdisciplinary masterplan for the city of Berlin demon-
strated one of the first attempts towards openness for an environmental lighting perspective
during a time when the scientific evidence on the impact of ALAN across urban and nat-
ural environments was still unclear. Ten years later, scientific research on the topic has
substantially increased.
4. Bridging Domains in the Collaborative Process
It is essential to understand that any successful collaborative process involves a
philosophy of empathic interactions that acknowledge the diverse languages, perspectives,
skillsets, backgrounds, and expertise of each domain [94].
The collaborative nature can potentially occur only as a dynamic interaction driven by
a shared interest as an emboldened modality [
95
], aimed at reducing the impact of artificial
lighting on the environment with solutions that address different night-time conditions
(e.g., cloudy nights or clear sky conditions) and different nightscape contexts.
In order to communicate crucial knowledge about ALAN (as a potential pollutant,
while also recognizing that ALAN is a tool to implement visual accessibility for users at
night), the lingua franca becomes a strategic asset and a frame of reference to communicate
the knowledge acquired by experts, the contrasting perspectives, and the platforms for the
transmission of evidence into practical solutions [96].
The language used to transfer information may serve to bridge the existing gaps
between practice, research, production, planning, and policy-making domains and may
enrich a shared empathic comprehension of the research questions and problems that each
domain is focused upon. Over the past century, the field of lighting design/technology
and the field of biology/environmental sciences have both developed key terms indepen-
dently of each other, in regards to the study of the night-time environment. However, the
interpretation of these definitions varies.
Int. J. Environ. Res. Public Health 2021,18, 624 9 of 18
Lighting professionals define properties of artificial lighting for the built environment
that consider human vision focused on the perception of brightness, contrasts, and colors in
objects under lighting conditions. Whereas, light pollution researchers and environmental
experts in biology, ecology, chronobiology, and light pollution developed a vocabulary
that identifies and describes the effect of natural and artificial light on biological processes,
living organisms, and ecosystems, as well as how environments and organisms affect each
other. The International Commission on Illumination (CIE)—the international authority on
light and lighting—recently created an online international lighting vocabulary [
97
], but
terms such as “ALAN” and “ecological light pollution” have not been defined [
98
]. The
CIE Technical Committee TC 4-61 has yet to produce a report and propose additions to
the missing definitions to reduce this communication gap between ALAN researchers and
lighting professionals.
Furthermore, the application of light can also greatly vary among scholars, experts,
and professionals in these fields. Lighting professionals see it positively for the visual
perception of built and natural landscapes at night and the added value it gives cities and
towns, which supports their visual appearance and so forth, however, this is often without
consideration of the possible consequences of added light. Whereas, environmental experts
consider artificial light as a component of society in need of careful management to reduce
the current negative burden on biodiversity and the natural environment.
It is important to stress that accessibility to knowledge in both domains requires
on-going interactions between the participants involved in order to build responsiveness
and potentially address current and emerging issues [
99
]. If guided incorrectly, it may
amplify the existing gap between lighting professionals and ALAN researchers, stoking
existing tension that may lead to uncertainties that disrupt the dynamic and co-learning
circumstances for each domain.
For instance, it is crucial to start with a dialogue about the problems that each field of
study addresses. Lighting professionals can attempt to answer the following questions:
How to design lighting schemes in urban environments that are based on research? What
lighting technology to implement? How to apply it for a specific project application?
Meanwhile, ALAN researchers can consider the following questions in their day-to-
day work: Based on the requirements of the lighting practice, what needs to be researched?
What properties in artificial lighting technologies are considered a light stressor? When is
it considered a stressor? [8,65].
The background and know-how of lighting professionals and ALAN researchers
may create new approaches and enrich techniques to achieve goals beyond the individual
narrative of each domain. The dialogue between experts may serve as a negotiating process
to address existing differences while creating a new vision to answer the question of how
to translate research knowledge to be applicable for the lighting practice.
Educational awareness on LP has also taken place by means of nonprofit organizations,
networks, and conferences.
The International Dark-Sky Association (IDA) [
100
], the Australasian Dark Sky Al-
liance [
101
], and other nonprofit organizations [
48
] educate communities and government
officials on the protection of night skies and biologically/ecologically responsible outdoor
lighting.
Additionally, the interdisciplinary and transdisciplinary network EU-COST Action
“Loss of the Night Network” (LoNNe, ES1204) presents projects, raises awareness pertinent
to ALAN, and stimulates an exchange of ideas and concepts [102,103].
Another form of knowledge exchange is via professional lighting and light pollution
conferences. Professionals and academics across disciplines gather at these events to ex-
change content related to the latest developments within their profession. These events
have become the locus of networking for likeminded and opposed individuals to discuss
root problems and information related to their field of study. Today, the international
conferences, as presented in Table 3, exchange an array of subjects with content strongly
focused on topics relevant to the expertise of its audience’s disciplines (e.g., lighting pro-
Int. J. Environ. Res. Public Health 2021,18, 624 10 of 18
fessional conferences for lighting professionals, the lighting industry and manufacturers;
light pollution conferences for academics, scientists, and experts on ALAN as a pollutant).
These conferences adhere to their statement of purpose (e.g., lighting professional confer-
ences present content relevant to the design practice, whereas light pollution conferences
present content relevant to light pollution and ecological light pollution, and technical
conferences present content relevant to technology and design focused on light as the
primary technical solution).
Table 3. Overview of lighting design and light pollution international conferences. Source: authors’ own work.
Conference Main Topics Focus
Light Pollution:
Theory, Modelling and
Measurements
(LPTMM)
Astronomical observations, theoretical concepts and solutions, numerical
modelling, and field campaigns on various topics that include the effects of
atmospheric aerosols, clouds, terrain, and obstacles on light pollution, the impact
of spectral and angular characteristics of light sources and reflecting surfaces,
observational techniques instrumentation, data and products, and the design and
evaluation of dark-sky-friendly lighting technologies, regulations, and outreach.
Scientific
European Symposium
for the Protection of
the Night Sky
Societal and cultural perspectives on light pollution, light pollution policy, citizen
science resources, biodiversity and ecology, sustainable development, and
outreach and initiatives.
Scientific
Artificial Light at
Night (ALAN)
Conference organized
by the steering
committee of the
ALAN Conference
Technology and design, e.g., artificial lighting technology, architectural lighting,
energy efficiency, outdoor lighting and street lighting; measurements and
modelling, e.g., citizen science, human exposure, modelling, remote sensing,
urban and pristine areas; society, e.g., economics, legislation, lighting governance,
lighting conflicts, outdoor lighting applications, perceptions of the night and the
preservation of natural areas, science and technological advancements, spatial
security, and the history of lighting; biology and ecology, e.g., biodiversity,
chronobiology, evolutionary adaptation, behavior, and food webs; health, e.g.,
circadian rhythm disruption, exposure to outdoor and indoor light, illness related
to ALAN, and melatonin.
Scientific
Practice-oriented
Professional Lighting
Design Convention
(PLDC) organized by
VIA Verlag
Lighting application case studies, professional practice issues, philosophy and
debate, office and retail lighting applications, plus workshops that include
excursions to view illumination projects.
Design
Practice-oriented
Enlighten Americas,
Europe, Asia
Conferences organized
by International
Association of Lighting
Designers (IALD)
Art, e.g., communicating design and the artistic/creative side of lighting design
(e.g., architectural lighting design (ALD) as an artistic medium), the artistic
process in projects, the poetics of lighting design, artistic conceptions, future
artistic trends, experimental design, and holistic approaches for lighting
applications; science, e.g., lighting technology (sources, controls, fixtures, and
software), development and trends, alternative energy sources (e.g., solar power),
the internet of things (IoT), project management strategies, control integration,
project case studies, cross-discipline topics and theory-based ideas, as well as the
latest research; professional tools, e.g., factors and challenges of the practice,
technology and creativity, business and social media, business and economy,
trends and business, management tools, client management skills, contract
negotiations, budgeting, marketing tools, as well as hiring and employee benefits.
Design
Practice-oriented
Annual Illuminating
Engineering Society
(IES) Conferences
organized by IES
Art, design, science and the research of lighting relevant to lighting professionals,
educators, and related design disciplines.
Technology and
Design
International
Commission on
Illumination (CIE)
Conferences
The physiology of human vision, vision and quality of light and colored light,
optical characteristics; light measurement methodologies, physical measurements
of light, photometry and the spectrum of light sources; interior lighting and
lighting design, quality of lighting, transportation and exterior applications;
photobiology, photochemistry; energy efficiency, LED lighting, renewable energy
sources; photobiological risk of artificial lighting.
Technology and
Science
Int. J. Environ. Res. Public Health 2021,18, 624 11 of 18
Interdisciplinary participation rarely occurs due to the narrow and specific require-
ments and protocols of these conferences. An exception is the ALAN conference series,
which is dedicated to examining all aspects of artificial light at night, including technology
and design, biology and ecology, and health. In recent years, an initiative has begun to
expand beyond the usual content and purpose statement in conferences and across disci-
plines (e.g., the presentation of empirical data on light pollution for lighting professional
conferences or the presentation of a project or urban lighting application for light pollution
conferences).
However, equitable transdisciplinary content is still required in order to evolve con-
ferences into an interchangeable platform to exhibit the utility of the lighting practice
and present evidence of artificial light as a pollutant. This commitment may provide
more perspective and offer appropriate tactics that broaden the interpretation of lighting
applications, as well as raise awareness about technological tools for urban environments.
Another step towards collaborative interactions between the practice and research of
lighting is defining platforms and networks to make knowledge transferable. Due to global-
ization, the rise of networking has increased interactions via international conferences [
104
]
and digital platforms [
105
], which render an opportunity to contextualize the exchange
of ideas. These tools serve as knowledge transfer mediums to facilitate transdisciplinary
and inclusive peer community praxis. They should be considered as a modus operandi to
develop potential alliances that reduce cultural and societal ambiguities experienced by
experts from different domains [
106
]. Again, the participation of the actors via knowledge
transfer platforms may empower dialogue and blur the existing boundaries between the
lighting practice, environmental research, and the policy-making of lighting, as well as the
lighting industry.
5. Urban Lighting Research Transdisciplinary Framework—Actors, Framework, and
the Four-Step Process
A theoretical principle of an organization towards sustainable lighting applications
should encourage the interaction of four main domains: research, practice, production
inputs, and policy-making and planning. The collaborative process between these four
pillars can potentially facilitate the understanding of data as knowledge, the application
of the acquired knowledge as standards to follow that may serve as guidance for the
development of lighting equipment, and the development of methodologies to design
lighting schemes protective of the night.
To gain knowledge, in the context of ALAN as a pollutant from applied lighting
technology, the Urban Lighting Research Transdisciplinary Framework (ULRTF) (Figure 2)
proposes the participation of four domains and various actors to distinguish the practices
and approaches of each field. It is of great importance to note that the lighting practice
is not a uniform domain as it is characterized by different strategies and techniques. For
instance, the main distinguishing difference between electrical illuminating engineers (e.g.,
street lighting engineers) and lighting designers (e.g., architectural lighting designers (ALD)
and urban lighting design ULD) is their approach to lighting applications. Street lighting
engineering is mainly focused on the application of visible luminaires to create homoge-
neous horizontal illuminance for pedestrian paths and vehicular circulation based on strict
technical lighting standards (e.g., by the European technical standard EN 13201, CEN).
In contrast, the approach of lighting design aims to create lighting for three-dimensional
spaces that focus on light as a medium on a surface and not the luminaire. Additionally,
the application of light by lighting designers integrates knowledge from different fields
(e.g., architecture, urban planning, industrial and product design, landscape design, and
perception psychology) to apply a modest presence of light on surfaces to sculpt volumes,
enhance materials, create gradients, and reveal shadows in a determined space and context,
as well make night-time spaces welcoming and user friendly.
Int. J. Environ. Res. Public Health 2021,18, 624 12 of 18
Int. J. Environ. Res. Public Health 2021, 18, x 12 of 17
Figure 2. Proposal for an urban lighting research transdisciplinary framework. Source: authors’
own work.
Table 3 presents a list of conferences as venues to exchange theoretic lenses on par-
ticular subjects of interest. These venues may offer an initial contact to a particular field of
expertise considered foreign, to expand the scope of knowledge and jargon, to implement
a preliminary social contact at an accepting level, to acquaint potential actors to establish
ULRTFs, and to potentially generate new platforms (e.g., conferences and technical com-
mittees). These new platforms may serve as settings to implement ULRTF with effective
communication and a periodic engagement of the actors in a collaborative fashion to-
wards lateral thinking strategies and problem-solving mechanics rather than dwelling on
monologues with essentially linear and vertical thinking [111]. ULRTF is a process to
mindfully consider when attending these conferences as these may provide venues to
meet potential actors to establish an opening to a collaboration framework [110].
Beyond the collaborative framework, it is also essential to establish a process with a
series of key steps to align, structure, and develop sustainable short- and long-term goals.
The collaborative development of steps and crucial processes can potentially favor the
dissemination of diverse knowledge and the expertise of each domain to create crossover
linkages of emerging approaches and procedures based on scientific practice curricula,
and to provide a platform for emerging transdisciplinary professionals that attempt to
involve scientific knowledge in their lighting practice. Table 4 presents an overview of a
proposed four-stage collaborative process that aims to involve lighting professionals in
urban lighting research.
Figure 2.
Proposal for an urban lighting research transdisciplinary framework. Source: authors’ own
work.
ALAN experts (e.g., astronomers, astrophysicists, chronobiologists, medical researchers,
ecologists, light pollution and ecophysiology experts, urban ecologists, urban evolution
researchers, and environmental researchers) focus on lighting applications with scientific
findings that assess the practice of lighting to consider light-sensitive species and ecosys-
tems and to preserve night-time environments, and experts from the remote sensing field
and instrument suppliers from the lighting industry (e.g., light source, luminaire and
lighting control manufacturers) provide the necessary assistance on research, including
light pollution data and the development of new lighting technologies, and testing tools to
assess the application of lighting (e.g., [
4
,
71
,
72
,
107
]). However, one cannot forget about the
users of this transdisciplinary collaboration, including urban planners, landscape designers,
policy-makers, planning officers, sustainability consultants, and environmental lawyers,
and their role in regulating fundamental aspects involving urban lighting masterplans and
assessing the application of ALAN that balances the safety and security of users while
considering nocturnality across nightscapes (e.g., [31,108–110]).
Table 3presents a list of conferences as venues to exchange theoretic lenses on partic-
ular subjects of interest. These venues may offer an initial contact to a particular field of
expertise considered foreign, to expand the scope of knowledge and jargon, to implement
a preliminary social contact at an accepting level, to acquaint potential actors to establish
ULRTFs, and to potentially generate new platforms (e.g., conferences and technical com-
mittees). These new platforms may serve as settings to implement ULRTF with effective
communication and a periodic engagement of the actors in a collaborative fashion towards
lateral thinking strategies and problem-solving mechanics rather than dwelling on mono-
logues with essentially linear and vertical thinking [
111
]. ULRTF is a process to mindfully
consider when attending these conferences as these may provide venues to meet potential
actors to establish an opening to a collaboration framework [110].
Beyond the collaborative framework, it is also essential to establish a process with a
series of key steps to align, structure, and develop sustainable short- and long-term goals.
The collaborative development of steps and crucial processes can potentially favor the
dissemination of diverse knowledge and the expertise of each domain to create crossover
linkages of emerging approaches and procedures based on scientific practice curricula,
Int. J. Environ. Res. Public Health 2021,18, 624 13 of 18
and to provide a platform for emerging transdisciplinary professionals that attempt to
involve scientific knowledge in their lighting practice. Table 4presents an overview of a
proposed four-stage collaborative process that aims to involve lighting professionals in
urban lighting research.
Table 4.
Overview of a proposed four-step process for lighting professionals in urban lighting research. Source: authors’
own work.
Steps Category Description
Step 1 Problem Definition
State the problem by clearly defining questions, identifying the topics involved, and
defining the existing solutions or case studies;
Develop background research on the defined problems by searching scientific and
lighting practice literature for comparison;
Translate problem-driven topics into research questions and hypotheses.
Step 2 Research Design
Development
Define the most appropriate properties of artificial lighting to be investigated during the
research study;
Determine the research procedure connected to artificial lighting;
Define and evaluate the parameters of lighting samples used in the future study;
Exchange and disseminate knowledge across disciplines related to the research;
Identify of the limitations of the study.
Step 3
Conducting Research
(Collecting and
Analyzing Data)
Partner across organizational boundaries to assess and exchange on current (local and
global) standards, regulations, and guidelines; to collect, exchange, and interpret data;
and for the use of measuring equipment, light sources, luminaires, and lighting control
types.
Step 4
Take Actions
(Reporting Research
Findings)
Translate and share research outcomes with the lighting practice in specific lighting
publications;
Co-write scientific research papers with other team members;
Speak at lighting conferences and seminars;
Develop guidelines and recommendations for the improvement of existing lighting
approaches based on teams’ research study outcomes.
6. Conclusions
The challenges of presenting collaborative perspective approaches for urban lighting
research rely on decoding various opportunities and practices that include the social
exchange of the actors, their professional motivation and purpose, and the collaborative
nature to structure processes that encompass the diversity of ideas.
This insight article presents a brief overview of the rapid development and application
of lighting technologies, which have unintentionally resulted in the widespread increase in
unnatural brightness, and the application of colors of light across landscapes in cities and
towns. Unfortunately, due to the problems distinctive to each separate field, the deeply
rooted and different perspectives present in the principles of each profession, along with
a lack of dialogue between them, this has resulted in a no-win/Gordian Knot situation.
Therefore, this work proposes the application of the urban lighting research collaborative
process as a community framework in order to identify the challenges that need to be
addressed, the similarities that should be shared, the steps and procedures that must be
followed, and the motivations and purposes that will help towards creating collective
ecological awareness. Furthermore, this paper presents a new and potentially useful model
for bringing different professionals together, where for the first time, lighting professionals
as key players are introduced into the collaborative process.
In conclusion, the proposed ULRTF relies on various opportunities and practices to
encourage the diversity of ideas in order to consider lighting parameters that operate
ecologically and deliver safe and secure measures for users at night.
Int. J. Environ. Res. Public Health 2021,18, 624 14 of 18
Moreover, this article also highlights the need for correctly designed urban lighting
research, and it proposes the collaboration of knowledge between environmental experts,
lighting professionals, and experts from other fields. Such a concept is envisaged as a
continuous work in progress with periodic adjustments, with the understanding that the
lighting practice is often ahead of the research field due to its knowledge of new technolog-
ical developments in urban lighting. Research studies on ALAN continue to exponentially
increase, which can provide an optimistic overview of the impending outcomes of the
practice. The reasonable and logical next phase will be to translate the acquired knowledge
of the research into practice to develop sustainable lighting concepts and techniques for
future nightscapes [8] and to build an ecologically conscious and responsive society [48].
Author Contributions:
All co-authors made substantial contributions to the manuscript. Concep-
tualization, C.P.V., K.M.Z.-D., and F.H.; writing—original draft preparation, C.P.V.; methodology,
K.M.Z.-D. and F.H.; writing—review and editing, C.P.V., K.M.Z.-D., and F.H.; supervision, K.M.Z.-D.,
and F.H. All authors have read and agreed to the published version of the manuscript.
Funding:
APC was covered by the Gda´nsk Univerity of Technology (GUT) for an online gold
open access publication. FH was supported by the ECOSLIGHT project of the European Union—
Agreement N◦612658-EPP-1-2019-1-EL-EPPKA2-SSA.
Institutional Review Board Statement: Not applicable.
Informed Consent Statement: Not applicable.
Conflicts of Interest: The authors declare no conflict of interest.
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