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Road lighting research for drivers and pedestrians: The basis of luminance and illuminance recommendations

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This article discusses quantitative recommendations for road lighting as given in guidelines and standards, primarily, the amount of light. The discussion is framed according to the type of road user, the driver and the pedestrian, these being the user groups associated with major and minor roads, respectively. Presented first is a brief history of road lighting standards, from early to current versions, and, where known, the basis of these standards. Recommendations for the amount of light do not appear to be well-founded in robust empirical evidence, or at least do not tend to reveal the nature of any evidence. This suggests a need to reconsider recommended light levels, a need reinforced by recent developments in the science and technology of lighting and of lighting research. To enable improved recommendations, there is a need for further evidence of the effects of changes in lighting: This article therefore discusses the findings of investigations, which might be considered when developing new standards.
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Road lighting research for drivers and
pedestrians: The basis of luminance
and illuminance recommendations
S Fotios PhD
a
and R Gibbons PhD
b
a
School of Architecture, The University of Sheffield, Sheffield, UK
b
Center for Infrastructure Based Safety Systems, Virginia Polytechnic
Institute and State University, Blacksburg, USA
Received 10 August 2017; Revised 2 October 2017; Accepted 5 October 2017
This article discusses quantitative recommendations for road lighting as given in
guidelines and standards, primarily, the amount of light. The discussion is framed
according to the type of road user, the driver and the pedestrian, these being the
user groups associated with major and minor roads, respectively. Presented first is
a brief history of road lighting standards, from early to current versions, and,
where known, the basis of these standards. Recommendations for the amount of
light do not appear to be well-founded in robust empirical evidence, or at least do
not tend to reveal the nature of any evidence. This suggests a need to reconsider
recommended light levels, a need reinforced by recent developments in the
science and technology of lighting and of lighting research. To enable improved
recommendations, there is a need for further evidence of the effects of changes in
lighting: This article therefore discusses the findings of investigations, which might
be considered when developing new standards.
1. Introduction
The Commission Internationale de l’Eclairage
(CIE) describes two main purposes of road
lighting: (1) to allow all road users, including
operators of motor vehicles, motor cycles,
pedal cycles and animal drawn vehicles to
proceed safely; and (2) to allow pedestrians to
see hazards, orientate themselves, recognise
other pedestrians and give them a sense of
security.
1
A third purpose is also given (to
improve the day- and night-time appearance
of the environment) but that does not fall
within the scope of this paper.
Guidelines and standards for road lighting
are provided to help designers achieve these
purposes, and to do so, they provide quanti-
tative recommendations for the appropriate
level (luminance or illuminance), colour
(or other characteristic derived from the
spectral power distribution (SPD)) and spa-
tial distribution of light. Example documents
include CIE 115:2010,
1
EN 13201-1:2014,
2
EN 13201-2:2015,
3
IESNA/ANSI RP-8:2014
4
and BS 5489-1:2013.
5
These are consensus
documents which means that they are written
and reviewed by committees representing a
cross-section of the industry – manufacturers,
designers, installers and researchers.
This paper discusses the basis of quantita-
tive recommendations for road lighting; the
background to current guidance, the need to
revise standards to respond to developments
in science and technology, and recent and
ongoing research being carried out to provide
an empirical basis for revised recommenda-
tions. The discussion is focussed upon
Address for correspondence: Steve Fotios, School of
Architecture, The University of Sheffield, Arts Tower,
Western Bank, Sheffield, S10 2TN, UK.
E-mail: steve.fotios@sheffield.ac.uk
Lighting Res. Technol. 2018; Vol. 50: 154–186
ßThe Chartered Institution of Building Services Engineers 2017 10.1177/1477153517739055
research into road lighting for pedestrians
and drivers, the categorisation used by the
CIE to distinguish between two sets of light-
ing recommendations.
1
The European stand-
ard EN 13201 also presents two sets of
recommendations, the M-classes and the
P-classes: the M-class is intended for drivers
on traffic routes; the P-class for pedestrians
and cyclists but also for drivers at low speeds
(40 km/h).
2,3
Road lighting is an extremely broad topic.
To limit the scope, we have not included
research of vehicle-mounted lighting, tunnel
lighting, conflict areas, the effects of or
measurement of glare, sign illumination, traf-
fic signals or parking and dedicated pathway
areas.
2. The basis of current road lighting
recommendations
2.1. Early standards
A road lighting standard is required to
ensure a good installation and to provide a
basis for tender.
6
In 1927, British Standard
307
7,8
identified eight classes of lighting,
defined by minimum mounting height and
maximum space:height ratio.
6
While min-
imum illuminances were also defined for
each of the eight classes, these ranging from
0.1 lux (0.01 foot candles) to 21.5 lux (2.0 foot
candles) at a test point, these minima were not
intended to be considered as a figure of merit
for the installation but only as a rating of its
size and had no theoretical basis.
6
The 1927
British Standard was suggested by Waldram to
be the first milestone in the technical progress
of street lighting. The second milestone,
Waldram suggested, was the 1928 field study
in Sheffield, UK, of 52 experimental installa-
tions, the problems observed in that study
leading promptly to a revised standard.
6
Many early standards tended to prescribe
lighting system characteristics rather than
performance metrics such as illuminance or
luminance, this being possible partly because
there were only a limited range of lamp
types available. For example, the 1974
British Standard gave recommendations for
between-post spacing according to road width
(Table 1).
9
This remained the primary
approach for lighting design until well into
the 1980s when the use of computers for
lighting design became commonplace.
10
It
was not until the 1985 British Standard,
11
based on CIE recommendations,
12
replaced
the 1974 Code of Practice
13
that photometric
objectives were explicitly stated, this being
done to allow the design to a pre-selected level
and uniformity of light.
10
2.2. Standards for driving
Two approaches have been used to set
lighting standards for traffic routes where
drivers are the primary road user: consider-
ation of visual function and consideration of
road accidents.
Table 1 Example of the ‘recipe’ method for prescribing road lighting criteria. This example is from British Standards
Code of Practice 1004:1974 part 2.
9
Light
distribution
class
Height
(m)
Minimum
lower
hemisphere
flux (lm)
Design space (m)
Effective road width (m)
11 12 13 14 15 16 17 18 20 22 24
Cut off 10 12,000 33 33 33 31 29 27 26 24 22
12 20,000 40 40 40 40 37 35 32 29 26
Semi cut off 10 12,000 44 44 42 40 36
12 20,000 53 53 52 47 43
Road lighting for drivers and pedestrians 155
Lighting Res. Technol. 2018; 50: 154–186
In North America, the initial approach for
establishing light levels was to consider how
changes in lighting affected the frequency of
road traffic collisions, and hence the safety of
vehicle occupants and the vulnerable road
users they hit. This is the basis of the
Illuminating Engineering Society of North
America (IESNA) road lighting recommen-
dations (originally implanted in 1972 but still
the basis of current standards in North
America), derived from the work of Box.
14
Box examined the relationship between illu-
minance and freeway (or motorway) crashes
on 203 miles of road. First, he considered the
presence versus absence of road lighting: the
day/night crash rate ratios for lit and unlit
roads were 1.43 and 2.37, respectively. Using
this ratio to calculate an expected crash rate,
Box concluded that installing road lighting on
freeways reduced nighttime crashes by an
average of 40%. Consider next the light level
(Figure 1): Box concluded that roads with the
lower range of illuminances (0.3 to 0.6 hori-
zontal foot candles (HFC), or 3.2 lux to
6.4 lux) had a lower night/day crash ratio
than roads with a higher range of illumin-
ances (0.8 to 1.1 HFC and 1.3 to 1.5 HFC;
8.6 lux to 11.8 lux and 14 lux to 16.1 lux). As a
result of these data, Box recommended a level
of 0.5 HFC (5.4 lux) for freeways. This result
seems counter to intuition as a higher lighting
level increased the crash rate ratio. It must be
remembered that additional lighting can
create additional glare and impacts the
driver’s adaptation level so while this result
is not expected, it may be justifiable.
There are limitations in the Box data. First,
Box performed only a limited statistical ana-
lysis: subsequent study has concluded the
data do not exhibit a relationship between
light level and crash rate.
15
This can be seen
by the regression lines shown in Figure 1;
while results for the four-lane roads are well-
fitted by a polynomial curve (R
2
¼0.97),
those for the six-lane road are not (R
2
¼0.02
for the linear fit is not improved by a
polynomial equation). Second, these values
were applied only to freeways; the levels for
other roadway categories had no empirical
backing. Despite these limitations, the
y = 0.014x2- 0.14x + 1.16
R
2
= 0.97
y = -0.0 15x + 1.8 5
R
2
= 0.02
0
1
2
3
0 5 10 15 20
Day night crash ratio
Illumin ance ( Lux)
4-Lane 6-Lane
Poly. (4-Lane) Linear (6-Lane)
Figure 1 Day/night crash ratio plotted against illuminance, after Box
14
156 S Fotios and R Gibbons
Lighting Res. Technol. 2018; 50: 154–186
0.5 foot candle illuminance determined by
Box has been carried through the standards
and translated into luminance criterion.
The first step in developing a metric based
on human vision was to establish an appro-
priate photometric quantity. This required the
use of luminance, which describes the lumi-
nous intensity per unit area in a given
direction, specifically that reflected from the
road surface towards the driver, and which
provides a better measure than illuminance of
how well an object can be seen. The lumi-
nance method, developed during the 1970s,
was documented by the CIE in 1982,
16
and
accepted by the IESNA in 1983.
17
In the
process of accepting luminance as the criteria,
the IESNA converted the existing illuminance
values to luminances based on the roadway
pavement classification.
The luminance of any point on a road
surface is a function of the illuminance on,
and the reflection properties of, the pavement
material. The luminance method therefore
requires knowledge of the road surface
properties and the geometry between the
light source and the observation position
relative to a point on the road surface. The
need to make assumptions about the obser-
vation point and viewing direction means that
luminance-based design is applied only to
situations such as motorways where the
assumption can be made. In conflict areas,
where multiple directions of view are likely,
illuminance-based design is retained. Road
surfaces are divided into a small number of
representative classes according to the type of
surface material and texture (in some coun-
tries, weather is also a factor), and for each
class, there is a representative road surface
reflectance table.
18
Field verification suggests that the targeted
design luminance is not always met, with
in-situ measurement of road surface lumi-
nance varying by up to 45% from the design
value.
19
One contribution to this difference is
uncertainty in the road surface reflectance
data,
20,21
for example, the age and the traffic
volumes on the pavement can vary the
reflection characteristics. Another limitation
is the difficulty in measuring luminance in-
situ with limitations from both the instru-
mentation and the logistics of performing the
measurements.
22
The luminance method is
also limited in adverse weather and wet road
surface conditions due to changes of surface
reflection.
23
The second step in developing a vision-
based system for lighting design was to
consider how changes in luminance (and
other road lighting characteristics) affect fac-
tors of visual performance such as the ability
and time taken to detect and identify objects.
Using lighting that increases the likelihood of
detecting a potential hazard and reduces the
time taken to achieve this detection leads to a
more rapid braking response. This in turn can
avoid accidents or at least reduce the severity
of an accident by reduction in the impact
speed. Indeed, studies have shown that road
lighting has a greater effect for reducing
fatalities and serious injuries than for minor
injuries.
15,24–26
Adrian
27
developed a model of visibility
based on the detection of a small object in the
roadway. This target was a square of 20%
reflectance, observed as a two-dimensional
flat object: with a side length 180 mm, it was
located at a distance ahead to subtend a visual
angle of 10 minutes of arc. The other inputs to
the model included a driver age of 63 years
and an observation time of 0.2 seconds. The
visibility level (VL) of an array of these
targets was calculated and a weighting func-
tion used to create a single metric that became
known as small target visibility (STV).
The definition of ‘small’ in STV is an
important factor. For smaller sizes, a slight
change in size can have significant effect on
visual performance whilst for larger sizes,
where performance is already at a plateau,
28
then changes in size may have negligible effect
on performance
29
(see also Section 4.1).
Road lighting for drivers and pedestrians 157
Lighting Res. Technol. 2018; 50: 154–186
The STV approach was implemented in the
US standard IESNA RP-8 in 2000.
30
In this
document, the IESNA allowed the use of
three methods for calculating lighting levels
on roadways; illuminance, luminance and
STV. Table 2 shows the recommended
values for this STV (VL) values and the
associated luminance criteria based on the
roadway type and the potential conflict levels.
It is interesting that the IESNA 2000 docu-
ment contradicted itself in using different
luminance values for the same roadway
criterion if luminance only was used as the
design metric (levels shown in Table 3) rather
than STV and luminance.
As any of the three criteria of illuminance,
luminance or STV could be used to establish
lighting designs, local agencies were able to
choose which. One of the issues with STV was
that it could not be field verified and, as a
result, the concept was discussed and
reviewed significantly, and in next version of
IES RP 8,
4
luminance was established as the
only design criteria; illuminance was used for
field verification and STV was used as a
selection criterion between designs.
STV is stated to be the basis of some road
lighting standards for drivers
31
although
standards themselves tend to be somewhat
vague about the basis of recommendations.
While it was hinted in CIE115:1995
32
that
visibility was the basis of the luminance
recommendations, it was also stated that
These recommendations are based on research
on and experience in all aspects of the visual
requirements at night’ and furthermore that
Although prescribed values of the criteria were
originally arrived at as a result of experimental
work, they have been tempered by experience
over this time ...’ Table 4 shows light levels
recommended in CIE115:1995 for the M-class
roads, where Table 6.1 of that document gives
recommendations without clear acknowledge-
ment of the basis and Table A1 of that
document gives recommendations based on
STV. This suggests that the main recommen-
dations were not based on STV. Note that M-
series of lighting classes as shown in Table 4
are ‘intended for drivers of motorized vehicles
on traffic routes, and in some countries also on
residential roads, allowing medium to high
driving speeds’;
1
for pedestrian and low
Table 2 STV values in IES-2000 based on roadway type and usage
30
Road and pedestrian conflict area STV criteria Luminance criteria
Road Pedestrian
conflict area
Weighting
average VL
L
avg
(cd/m
2
) Uniformity ratio
Median
strip 57.3 m
Median
strip 47.3 m
L
max
/L
min
(maximum allowed)
Freeway Class A 3.2 0.5 0.4 6.0
Freeway Class B 2.6 0.4 0.3 6.0
Expressway 3.8 0.5 0.4 6.0
Major High 4.9 1.0 0.8 6.0
Medium 4.0 0.8 0.7 6.0
Low 3.2 0.6 0.6 6.0
Collector High 3.8 0.6 0.5 6.0
Medium 3.2 0.5 0.4 6.0
Low 2.7 0.4 0.4 6.0
Local High 2.7 0.5 0.4 10.0
Medium 2.2 0.4 0.3 10.0
Low 1.6 0.3 0.3 10.0
STV: small target visibility; VL: visibility level. Median strip: the reserved area (central reservation) separating opposing
lanes of traffic on dual carriageways and motorways. The table refers to the width of the strip.
158 S Fotios and R Gibbons
Lighting Res. Technol. 2018; 50: 154–186
speed traffic areas, the P-series of lighting
classes is used.
1
Table 5 shows the light levels recom-
mended in CIE115:2010 for the M-series of
lighting classes and Table 6 shows the par-
ameters by which an appropriate class is
selected. To establish a lighting class, the
appropriate weighting values from Table 6
are summated, and this total subtracted from
6: the resultant value is the M-class (or, if this
is not a whole number, the next lower whole
number is used). A similar approach is
used to establish a class within the P-series
(Tables 7 and 8). Differences between
the 2010 and 1995 issues of CIE115 are the
extension from five to six classes in the
M-series, the main change being the addition
in 2010 of class M6. The method of choosing
a class also changed, being a narrative
description of road type in 1995 and a
quasi-objective approach in 2010.
2.3. Standards for pedestrians
Lighting in minor roads, often called sub-
sidiary roads, is intended to target the needs
of pedestrians. For example, BS5489-1:2013
states that the main purpose of lighting for
subsidiary roads and areas associated with
those roads is ‘‘to enable pedestrians and
cyclists to orientate themselves and detect
vehicular and other hazards, and to discourage
crime against people and property.
5
The light-
ing on such roads can provide some guidance
for motorists, but is unlikely to be sufficient for
revealing objects on the road without the use of
headlights’’. CIE guidance
1
states that ‘The
road lighting should enable pedestrians to
discern obstacles or other hazards in their
path and be aware of the movements of other
Table 3 Luminance values in IES-2000 based on roadway type and usage
30
Road and pedestrian conflict area Average
luminance
(cd/m
2
)
Uniformity ratio Veiling luminance ratio
L
vmax
/L
avg
(maximum allowed)
L
ave
/L
min
(maximum
allowed)
L
max
/L
min
(maximum
allowed)
Road Pedestrian conflict area
Freeway Class A 0.6 3.5 6.0 0.5
Freeway Class B 0.4 3.5 6.0 0.3
Expressway High 1.0 3.0 5.0 0.3
Medium 0.8 3.0 5.0 0.3
Low 0.6 3.5 6.0 0.3
Major High 1.2 3.0 5.0 0.3
Medium 0.9 3.0 5.0 0.3
Low 0.6 3.5 6.0 0.3
Collector High 0.8 3.0 5.0 0.4
Medium 0.6 3.5 6.0 0.4
Low 0.4 4.0 8.0 0.4
Local High 0.6 6.0 10.0 0.4
Medium 0.5 6.0 10.0 0.4
Low 0.3 6.0 10.0 0.4
Table 4 Comparison of average luminances recom-
mended in CIE115:1995 in Table 6.1 and also Appendix
A Table A1, which gives lighting requirements ‘when the
STV concept is used’
32
Lighting
class
Table 6.1
Average
luminance
(cd/m
2
)
Table A1
Visibility
level
Average
luminance
(cd/m
2
)
M1 2.0 7.5 1.0
M2 1.5 7.0 1.0
M3 1.0 6.0 0.7
M4 0.75 5.5 0.5
M5 0.50 5.0 0.5
Road lighting for drivers and pedestrians 159
Lighting Res. Technol. 2018; 50: 154–186
pedestrians, friendly or otherwise, who may be
in close proximity’.
An early distinction between types of road
user occurred in the 1930s when the British
Minister of Transport set up a committee to
examine the efficient provision of road
lighting with particular reference to ‘the
requirements of residential and shopping
areas’.
6
This led to recommendations for
only two classes of lighting – traffic routes
and other roads requiring lighting – with the
Table 6 Weighting factors for selecting an M-class of
road lighting
1
Parameter Option Weighting
value
Speed Very high 1
High 0.5
Moderate 0
Traffic volume Very high 1
High 0.5
Moderate 0
Low 0.5
Very low 1
Traffic composition Mixed with high
percentage of
non-motorised
2
Mixed 1
Motorised only 0
Separation of
carriageways
No 1
Yes 0
Intersection density High 1
Moderate 0
Parked vehicles Present 0.5
Not present 0
Ambient luminance High 1
Moderate 0
Low 1
Visual guidance/
traffic control
Poor 0.5
Moderate or good 0
Table 7 P lighting classes from CIE
1
Lighting
class
Average
horizontal
illuminance
(lux)
Minimum
horizontal
illuminance
(lux)
Additional requirement
if facial recognition
is necessary
AB
P1 15 3.0 5.0 3.0
P2 10 2.0 3.0 2.0
P3 7.5 1.5 2.5 1.5
P4 5.0 1.0 1.5 1.0
P5 3.0 0.6 1.0 0.6
P6 2.0 0.4 0.6 0.4
A. Minimum vertical illuminance (lux).
B. Minimum semicylindrical illuminance (lux).
Table 8 Weighting factors for selecting a P-class of road
lighting
1
Parameter Option Weighting
value
Travel speed Low 1
Very low 0
Traffic volume Very high 1
High 0.5
Moderate 0
Low 0.5
Very low 1
Traffic composition Pedestrians, cyclists
and motorised
traffic
2
Pedestrians and
motorised traffic
1
Pedestrians and
cyclists only
1
Pedestrians only 0
Cyclists only 0
Parked vehicles Present 0.5
Not present 0
Ambient luminance High 1
Moderate 0
Low 1
Facial recognition Necessary Additional
requirements
Not necessary No additional
requirements
Table 5 M lighting classes for dry roads from CIE
1
Lighting
class
Average
luminance
(cd/m
2
)
Overall
uniformity
Longitudinal
uniformity
M1 2.0 0.40 0.70
M2 1.5 0.40 0.70
M3 1.0 0.40 0.60
M4 0.75 0.40 0.60
M5 0.50 0.35 0.40
M6 0.30 0.35 0.40
Note: Not shown here are recommendations for wet
surface uniformity, threshold increment and surround
ratio.
160 S Fotios and R Gibbons
Lighting Res. Technol. 2018; 50: 154–186
intention that lighting on traffic routes should
be sufficiently good for drivers to proceed
safely without the use of headlights.
6
The 1992 British Standard recommended
three lighting classes for subsidiary roads,
these having horizontal illuminances of
3.5 lux, 6.0 lux and 10 lux, with the choice
defined by a narrative description of the
typical application.
33
These illuminances
were derived largely from a field study in
which a small group of people evaluated the
‘general impression’ of lighting in 24 locations
using a nine-point category rating scale.
34
The
three horizontal illuminances were proposed
as they corresponded to ratings of good (7),
adequate (5) and poor-to-adequate (4) on the
nine-point scale. The results, however, are
likely trivial, being influenced by stimulus
range bias,
35
and the field survey did little
more than stretch the range of illuminances
encountered in the survey to fit the response
scale. Stimulus range bias means that a field
survey in which a different range of illumin-
ances had been observed would have indi-
cated that different illuminances correspond
to ratings of good, adequate and poor, and
this can be seen in the earlier, but unfortu-
nately unconsidered, field survey reported by
de Boer.
35,36
While it is possible in hindsight to criticise
evidence for the 1992 British standard, there
was at least an intention to base the guidance
on empirical evidence, and that is not appar-
ent in later guidelines. In 1995, CIE recom-
mended six lighting classes, with average
horizontal illuminances ranging from 1.5 lux
to 20 lux.
32
In 2003, EN 13201-2:2003 also
recommended six lighting classes but with a
narrower range of illuminances (2.0 lux to
15 lux),
37
and this range was retained in later
updates to standards.
1,3
Other than the
Simons et al. field study described above,
the empirical evidence for these recommen-
dations, if any, is unknown.
Table 7 shows the light levels recom-
mended for pedestrians and Table 8 shows
the weightings provided with which to deter-
mine which of the six lighting classes of
Table 7 is appropriate for a given situation.
These are the recommendations of CIE,
1
but
those of EN 13201-1:2014 and EN 13201-
2:2015 are similar.
2,3
This similarity between
the two documents is unsurprising since
many of the members on the CIE committee
are also members of the CEN committee’,
38
which is not the same as independent groups
reaching similar conclusions.
There are a number of unknowns in these
data. First, consider that the fundamental
element is the mean horizontal illuminance:
there is no published explanation of the basis
for these values. This lack of support means
designers are unable to consider whether their
requirements are met and researchers have no
basis for direct criticism.
Second, consider the supplementary illu-
minance values. The ratio of minimum to
average horizontal illuminance is 0.2 in every
class, which suggests convenience rather than
an empirical basis. For the facial recognition
criteria, the ratio of horizontal illuminance to
vertical illuminance is about one-third and the
ratio of horizontal illuminance to semi-cylin-
drical illuminance is 0.2, again suggesting
convenience rather than an empirical basis.
There are no known reasons for these criteria
and the consistent ratios suggest they were
not independently evaluated but are simply
an arbitrary ratio.
Additional criteria for facial recognition
are provided for situations where facial rec-
ognition is considered to be necessary, but
without comment as to when facial recogni-
tion may or may not be necessary. The
additional criteria are minimum values of
vertical or semi-cylindrical illuminance to be
considered alongside minimum horizontal
illuminance. The face of another person
tends to be largely a vertical surface and
hence ensuring an adequate illuminance on
the vertical plane may be beneficial. Semi-
cylindrical illuminance is provided as an
Road lighting for drivers and pedestrians 161
Lighting Res. Technol. 2018; 50: 154–186
alternative measure, possibly because the
basis of this measure (the averaged illumin-
ance on the curved surface of an upright
semi-cylinder) is believed by some to better
characterise the ability to evaluate faces.
39
This is unlikely to be the case because a single
value of semi-cylindrical illuminance provides
no more information about spatial distribu-
tion than does a single value of vertical
illuminance. The belief in semi-cylindrical
illuminance appears to come from two
studies, which plotted semi-cylindrical illu-
minance against results of facial recognition
experiments,
40,41
but without fair comparison
of the alternatives,
39
and ignoring that other
studies
34,42,43
had concluded that semi-cylin-
drical illuminance did not offer an advantage
over horizontal or vertical illuminance.
39
Third, consider that a lighting class is
chosen with consideration to five parameters:
travel speed, traffic volume, traffic compos-
ition, parked vehicles and ambient luminance
(Table 8). An immediate response to these
parameters is that they have limited relevance
to the stated purposes of road lighting, i.e. to
enable pedestrians to discern obstacles or other
hazards in their path and be aware of the
movements of other pedestrians, friendly or
otherwise, who may be in close proximity’.
1
Instead, they relate largely to the potential
for, and severity of, collision with a motor
vehicle. Whilst that is clearly an important
consideration, the disconnection between the
stated aims of lighting and the approach to
choosing how much light is provided does not
provide confidence that the intended purpose
will be met.
There is some evidence that travel speed,
44
traffic volume,
45
traffic composition
46
and the
presence of parked vehicles
47
are associated
with the risk of accident/injury to pedestrians.
There is not, however, any evidence that
differences between the options are fairly
represented by a weighting of 1.0 in all
cases, in particular since the options are not
clearly defined, and there is no evidence that
the weightings should be considered to be
cumulative. Guidance for Australia and New
Zealand provides an alternative set of weight-
ing factors,
48
for which the options are better
defined (e.g. there are quantitative values of
traffic volume rather than being labelled very
high, high, moderate, etc.) and the weightings
appear to be more nuanced.
This means the weighting factors may be
leading to lighting design conditions that are
not appropriate, possibly too high and lead-
ing to excessive energy consumption and light
pollution, or too low and leading to insuffi-
cient visual benefit for pedestrians. For exam-
ple, while a mixed traffic composition may
benefit from a higher illuminance than single-
type traffic, this approach does consider
whether the illuminance provided by the
lower P-classes (e.g. class 4 or 5) may already
be sufficient to meet the demands of mixed
traffic.
3. The need for new standards
A fundamental need for standards to be
reviewed is that they do not appear to be
founded in robust empirical evidence. Such
evidence is needed first to show that the
assumed benefits of lighting do exist (i.e.
improved visibility, improved safety,
improved feeling of safety), and second to
show how these benefits might be affected by
changes in context and changes in lighting.
Furthermore, within recent years, there have
been developments in the technology of road
lighting and the technology of research, and
developments in our understanding of vision
and the side-effects of road lighting.
3.1. Developments in science and technology
Waldram
6
and the online archive of Simon
Cornwell
49
describe developments in the tech-
nology of road lighting. In 1405, the
Aldermen of The City of London were
ordered to see that a lighted lantern was
162 S Fotios and R Gibbons
Lighting Res. Technol. 2018; 50: 154–186
hung outside every house along the road
(‘highway’ in the original), followed in 1461
by a standard specification for the candles.
Gas lamps were first used in London in 1807,
followed a few years later, in 1816, by
arguments in the Cologne Zeitung newspaper
against lighting at night (with arguments
including that ‘the fear of darkness will
vanish and drunkenness and depravity
increase’). Arc lamps were used to light
public areas in Paris (1878) and Cleveland
(1879). In London, arc lighting and incandes-
cent lighting were introduced in the 1880s.
The introduction of discharge lamps in the
1930s is described by Waldram
6
as the third
milestone in street lighting, because ‘engineers
were presented with lamps with almost the
simplicity of the filament lamp, with three
times the efficiency and twice the life. Public
lighting could be provided on a scale and to a
level which was previously not economically
possible’. One problem with discharge lamps
compared with the filament and gas lighting
they replaced, was that they ‘gave light of an
unfamiliar colour which has strange and unflat-
tering effects on personal appearance’; new
installations were a matter of public interest
with the result that ‘local authorities began to
demand better lighting and to be prepared to
pay for it’.
6
Low pressure sodium (LPS) lamps were
first installed in 1932, high pressure mercury
vapour in 1933, fluorescent in 1946 and high
pressure sodium (HPS) in 1966.
49
There are
three limitations with these types of lamp.
First, there were limited options for SPD,
which for LPS and HPS lamps meant a
yellowish-orange appearance and a low
colour rendering index. Second, these were
large lamps (LPS lamps in particular) and
gave limited opportunity for optical control,
leading to an assumption that if one part of
the roadway was well lit, then an adjacent
footpath would also be well lit. Third, other
than some types of fluorescent lamp, they
have switching-on cycles, which can require
several minutes to reach full output. These
limitations are removed with the implemen-
tation of Solid State Lighting (Light Emitting
Diodes – LEDs) in roadways and outdoor
areas. LEDs can have very fine optical
control due to the small size of individual
units, almost limitless control over SPD if
sufficient primaries are used, and can be
switched on and off instantaneously. The
introduction of LEDs has thus led to new
requirements for new recommendations asso-
ciated with spectrum, spatial distribution (e.g.
the surround ratio and specific sidewalk
requirements
50
) and dynamic control. The
small physical size of LEDs renders new
applications possible. For example, using
self-luminous road studs as lane markers
may provide a better solution than overhead
road lighting in some situations.
51
This is
likely to reduce sky glow and energy
consumption.
While visual conditions under road lighting
are likely to fall within the mesopic region,
where both rods and cones provide significant
responses, road lighting recommendations are
given using photopic quantities. That is, the
recommended illuminances (or luminances)
are derived from the CIE standard photopic
observer
52
and hence ignore any contribution
from the rods (and short wavelength sensitive
cones). Since rods and cones display different
spectral sensitivities, a photopic-only
approach may not be adequately accounting
for changes in the SPD of road lighting. That
limitation has become more important since
the widespread introduction of LEDs which,
compared with sodium and mercury lamps,
significantly enhance the opportunity to
change and tune SPD.
One recent development in road lighting
measurement is the establishment of a system
for mesopic photometry,
53
with work cur-
rently ongoing to establish how it should be
applied in practise.
54
The mesopic system was
derived from two parallel bodies of work, the
European MOVE consortium
55–58
who used
Road lighting for drivers and pedestrians 163
Lighting Res. Technol. 2018; 50: 154–186
laboratory experiments with three represen-
tative visual tasks – can it be seen, how
quickly and what is it? – and the Lighting
Research Center
59
who used reaction time to
detection of peripheral targets in experiments
of ascending practicality related to driving:
An abstract target,
60
a driving simulator,
61
and driving on a test track.
62
The mesopic
visual response is essentially a weighed com-
bination of the scotopic (S) and photopic (P)
responses, and hence the CIE mesopic
system
53
provides the weighting factor
according to the level of adaptation and the
S/P ratio of lighting, this being established by
consensus between the two bodies of work.
A focus of current research is how to define
the level of adaptation.
63,64
While there is now a system for mesopic
photometry still to be resolved is the situ-
ations where it should be applied. For some
driver-related activities, mesopic models may
not be applicable,
65,66
a result of the dimin-
ishing use of peripheral vision during driving
on main roads, the ever changing adaptation
luminance due to the dynamic nature of
drivers’ eye movements, and the simultaneous
use of headlights. The CIE system has been
applied, however, in pedestrian lighting rec-
ommendations,
5,67–69
to characterise the illu-
minance reduction permitted when using
lighting of greater short-wavelength content,
this being of benefit for tasks such as obstacle
detection
70,71
and spatial brightness percep-
tion.
72
Alongside the S/P ratio, a minimum
value of colour rending is also prescribed,
arbitrarily set at R
a
¼60 for consistency with
the previous version of BS5489,
73
to avoid
encouraging the use of extremely high S/P
ratios.
68
There have also been developments in
technology associated with road lighting
research.
In-situ light measurement techniques with
cameras and illuminance meters linked to a
GPS coordinates to evaluate lighting instal-
lations over large distances
15
;
An efficient form of lighting would be to
light only what road users tend to look at.
While eye tracking has long been possible,
the recent development of mobile eye
tracking has made it much easier to inves-
tigate where people tend to look whilst
travelling
74–77
;
Systems that allow for monitoring of in-
vehicle driver behaviour and the assessment
of the impact of roadway conditions on
that behaviour
78
;
The calculation of road surface luminance
(and other properties) is a complex task.
One development that reduced the effort
demanded was the introduction of the
desktop personal computer.
A further development may change radic-
ally the approach to lighting, at least on
traffic routes. That is the introduction of
autonomous (driverless or hands-free) motor
vehicles,
79
which offer the promise of fewer
accidents due to automated collision avoid-
ance systems. The need for lighting is reduced
if the driver is not required to search for
hazards, provided of course that all vehicles
are autonomous and that the collision avoid-
ance system do not fail, which is a high
expectation. One potential benefit of the
detection systems is that they may be able to
communicate with the road lighting system to
allow the road lighting to be adjusted (e.g.
switched on or luminance increased) in
response to an approaching vehicle.
3.2. Side-effects of road lighting
The aim of lighting guidance should be to
ensure that the correct quantity and quality of
lighting is used, where and when it is of
benefit. Lucas et al.
80
referred to the man-
agement and use of light being similar to
administering a drug: light has both benefits
(positives) and unwanted side-effects (nega-
tives) giving the need to control the dosage of
the light so as to provide the maximum
benefit whilst minimising the negatives.
164 S Fotios and R Gibbons
Lighting Res. Technol. 2018; 50: 154–186
One reason to suspect that light levels are
on the high side and could be reduced is that
they have tended to rise with time. For
example, the maximum recommended illu-
minance for subsidiary roads in the UK
increased from 10 lux in 1992
33
to 15 lux in
2003.
37
Figure 2 shows the tendency for the
average illuminance of street lighting in
Britain to increase with time, as determined
by Crabb et al.
81
from data presented by
McNeill.
82
Changes in technology have
moved towards lamps of greater efficacy
and light levels may have increased, because
there was an ability to do so, not because
there was evidence of a benefit to be gained
from higher light levels.
In 1972, Waldram discussed the ‘sky haze
due to street lighting.
83
The discussion of sky
glow has continued,
84–87
showing, for exam-
ple, that the use of LEDs of high CCT
(6500 K) increases scattered light and hence
sky glow compared with conventional sources
of lower CCT.
85
Too much light or an
inappropriate quality of light might also
lead to wasteful energy consumption,
88
to
light trespass on property
89
and to unwanted
impact on the natural environment.
90
While
there are strong lobbies to reduce the impacts
of these externalities, by using lower light
levels, restricted spectral tuning or optical
control, recommendations still need to meet
the intended benefits for road users, e.g. a
pedestrian’s ability to detect a trip hazard or a
driver’s ability to detect a pedestrian on the
carriageway. For this, we need robust evi-
dence of how such benefits are affected by
changes in lighting and this is not evident in
existing standards.
One impact of lighting side-effects is that
there may be a need to consider additional or
alternative recommendations. The average
illuminances and uniformity of current stand-
ards may no longer be sufficient and future
standards may need to include maximum light
levels, limitations for SPD and spatial distri-
bution and exposure doses.
4. Lighting for drivers
Research undertaken to establish the benefits
of road lighting for drivers can be divided into
0
2
4
6
8
10
12
14
1900 1920 1940 1960 1980 2000 2020
Average illuminance (lux)
Year
Figure 2 The average illuminance of street lighting in Britain has tended to increase
81,82
Road lighting for drivers and pedestrians 165
Lighting Res. Technol. 2018; 50: 154–186
three broad types: Laboratory studies of
visual function, driving performance investi-
gated using simulators or test tracks and
studies of the relationship between different
types of lighting and the frequency (and/or
severity) of road traffic collisions. The first of
these shows how lighting affects those aspects
of fundamental visual functions considered
pertinent to driving. The second considers
holistic driving performance or visual func-
tion within the context of other cognitive
demands of driving. The third considers how
lighting affects the outcome of driving
performance.
4.1. Laboratory studies of visual function
The relationship between light level (lumi-
nance) and visual performance tends to
follow a plateau-escarpment relationship
28
;
at low light levels, an increase in luminance
brings significant increase in visual perform-
ance (the escarpment), but a point is reached
beyond which further increase in luminance
no longer increases visual performance (the
plateau). Identifying this point of transition is
one approach to establishing the optimum
luminance for a task.
Identification of a target is an on-axis task
and performance may be characterised by
acuity. For foveal acuity, the data suggest
that higher luminance may enhance acuity
but do not suggest that changes in SPD have
significant effect.
91–93
SPD is expected to have
an effect on visual performance, in mesopic
conditions, for targets that stimulate regions
of the retina beyond the fovea, either by size
or by off-axis location. This can be seen in the
study by Lewis
94
who measured threshold
luminance contrast of back-illuminated trans-
parencies of sinusoidal contrast gratings,
which subtended a visual field of approxi-
mately 138wide and 108high. At luminances
of 10.0 and 3.0 cd/m
2
, there was no difference
between the three lamps examined (MH,
HPS, LPS), but as the average photopic
luminance decreased further into the mesopic
(1.0 and 0.1 cd/m
2
), then an effect of SPD
became apparent, with the MH lamp having
significantly lower relative luminance contrast
threshold than the HPS or LPS lamps. It
should be noted that further research indi-
cated that in a driving environment, the
mesopic effect was minimised at higher
speeds do the reduction in the use of the
peripheral vision and blur due to visual flow
through the field of view.
65
The reaction time to detection of a target is
suggested to be of direct relevance to driving
performance as the speed of detection plays
an important role in perceptual judgements
made by the driver and can be easily
translated into stopping distances.
95
Several
studies
60,94,96,97
have investigated detection
rate and reaction time to detection, for on-
axis and off-axis targets, under different
luminances and SPDs. The effect of SPD on
detection can be characterised by the S/P
ratio (the ratio of scotopic (rod) to photopic
(cone) photoreceptor responses). For off-axis
targets, at luminances within the mesopic
region, lighting of higher S/P ratio tends to
reduce the reaction time to detection and
increase detection rate. For example, in He
et al.,
60
who compared reaction times under
HPS and MH lamps to the onset of an
achromatic 28disc, presented 158off-axis, the
benefit of higher S/P ratio was observed for
luminances below approximately 1.0 cd/m
2
.
The significance of SPD for the detection of
peripheral targets may, however, depend on
the characteristics of the target and the
independent variable used to quantify
detection.
98
Researchers have attempted to develop a
model of lighting based on visual perform-
ance. Hills considered the visibility of tail
lights, road surface obstacles and pedestrians,
and characterised this using the luminance
difference between the target and background
and the visual size of the target.
99
Davison
reported that the association between funda-
mental measures of visual performance
166 S Fotios and R Gibbons
Lighting Res. Technol. 2018; 50: 154–186
(e.g. acuity) and driving performance was
weak and suggested instead the need to
consider contrast sensitivity.
100
VL provides
one way of doing this. Consider the lumi-
nance of a target object and its background:
VL is the ratio of the actual difference in
luminance to the luminance difference at
threshold, calculation of this threshold
giving consideration to contrast polarity,
observation time and observer age.
27
As VL
increases above 1.0, an object starts to appear
in silhouette. Subsequent research has been
carried out to explore VL and establish the
value of VL needed for adequate visibil-
ity.
101,102
Most recently, Buyukkinaci
et al.
103
found that VL 7.0 ensured the
target could be detected, established using
four target reflectances (0.2 to 0.5) under four
classes of lighting (M2 to M5): note that these
are higher levels of visibility than adopted in
Appendix A of CIE115:1995.
32
Detection is affected by the size and
reflectance (and hence luminance) of the
target.
99
A standardised target of size
200 mm 200 mm is used in some studies,
this being considered the smallest size of
object which might be dangerous to traffic.
104
At 100 m ahead this subtends a size of 7 min.
CIE115:1995 refers to a smaller target
(180 mm 180 mm) but located at a closer
distance, 83 m ahead of the observer, and
which hence subtends a similar visual size. In
CIE115:1995, the STV target had a luminance
reflectance of 20%. Reflectance is an inter-
esting issue for hazard detection. Road light-
ing illuminates the road surface and an object
is revealed by negative contrast (silhouette)
against the light background: objects of low
reflectance are easily perceptible. Vehicle head
lighting illuminates vertical surfaces and an
object is revealed in positive contrast against
the dark background; objects of high reflect-
ance are easily visible but those of low
reflectance are not.
104
Some studies have revealed limitations of
the STV approach. Lecocq
105
raised concern
about the use of STV in wet conditions;
Menard and Cariou
102
suggested that the
small target was of little use in evaluating the
visibility of pedestrians; Raynham
31
ques-
tioned the validity of such a simple object
for real obstacles.
One limitation of vision-based models is
that they tend to consider only one, or
a limited number of, the myriad features of
a visual task (size, contrast, location of target)
encountered in the real world. The next
approaches to be considered overcome this
limitation by considering the outcomes of a
change in lighting, on either driving behav-
iour or accident rates.
4.2. Driving performance
Driving performance can be examined
whilst using a simulator or driving a real car
on either a test track or open road. Following
studies which had examined peripheral detec-
tion in laboratory situations,
60,61
Akashi
et al.
62
examined detection while participants
drove along a test track. Rather than using an
abstract response task to note detection of a
peripheral target, their test participants were
required to use the brake and accelerator
pedals to indicate detection. While such an
approach is a step toward better ecological
validity compared with button pressing, it
was still a direct response to detection.
Measures of driving performance include
the mean and variance of vehicle speed and
lateral position, or driver actions such as
steering wheel control.
106
In a simulator
study, Shahar et al.
51
examined lane control
on a curved section of rural road, the road
being either unlit (i.e. no road lighting but
headlighting was in use), conventionally lit, or
unlit but using self-luminous (LED) road
studs. They examined the standard deviation
of lateral position because this gives some
idea of the driver’s control over the vehicle.
For left-hand turns, the standard deviation of
lateral position was lower for driving with
road studs than for either the lit or unlit
Road lighting for drivers and pedestrians 167
Lighting Res. Technol. 2018; 50: 154–186
road: for right-hand turns, there was a smaller
standard deviation for the road studs than
the unlit road, but not smaller than for the
lit road.
In a large scale field study, Li et al. fitted
approximately 2500 cars across seven states of
the USA with data collection systems, includ-
ing video and in-vehicle sensors.
107
Every trip
in these vehicles was monitored for more than
one year. The resultant database provides a
rich database of driver behaviour. The light-
ing data collection of the previously described
project was captured in two US states that
overlap with the driver behaviour data col-
lection.
15
Combining these two data sets
allows for an analysis of the impact of lighting
in specific portions of the roadway.
Initial results suggest, for example, that
increasing the illuminance of the near-side
lane (right-hand lane in the US) at an
interchange reduced the driver speed and
lateral acceleration (Table 9). In this research,
the ramps at entrances to the roadway (EN
categories) and exits from the roadway were
divided into five sections for analysis. The
significant driver behaviour changes in each
of these areas were then calculated and shown
with an arrow. The arrow pointing up
indicates an increase in the metric considered
(i.e. speed, lateral acceleration, etc.) and an
arrow down represents a decrease. These
results show that the lighting can impact a
driver’s behaviour, and hence that light in
specific locations on the roadway can pro-
mote a behaviour that provides a higher level
of safety. A single light level for all sections of
a roadway may not be the most effective
approach.
4.3. Lighting and road accidents
Investigating the association between
changes in lighting and the frequency and/or
severity of road traffic accidents is an out-
comes-based approach to setting light levels.
While it does not directly examine why a
change in lighting leads to measured outcome,
accident reduction is the benefit part of the
cost–benefit approach used in some cases
to justify installation of road lighting. For
example, a UK manual assumes reductions in
personal injury accidents of 10% on motor-
ways and dual carriageway roads and 12.5%
on single carriageway roads.
108
In contrast, in
New Zealand, it is assumed that upgrading or
improving lighting leads to a 35% reduction
in crashes.
26
Table 9 Impact of an increase in the illuminance on driver behaviour
Analysis segment Traffic type Right-lane illuminance Overall illuminance
EN1 EN2 EN3 EN4 EN5 EN1 EN2 EN3 EN4 EN5
Speed Ramp – – &&NS NS %NS
Through NS NS NS NS NS NS NS %NS NS
Longitudinal acceleration rate Ramp %%%––%&&
Through NS NS NS %%NS NS NS &&
Longitudinal acceleration
variance
Ramp NS NS NS NS NS NS
Through NS NS NS &NS NS NS NS NS NS
Lateral acceleration rate Ramp &&&––%%NS
Through &NS &NS &%NS %%%
Lateral acceleration variance Ramp NS NS NS NS NS NS
Through NS NS &NS NS NS NS %NS NS
Lane offset Ramp NS NS & NS NS %
Through NS NS NS NS NS NS NS NS NS NS
These data are for the entrance ramp.
107
&indicates a decrease in the behaviour; %indicates an increase in the behaviour.
NS: not significant; EN: entrance category.
168 S Fotios and R Gibbons
Lighting Res. Technol. 2018; 50: 154–186
In 1992, the CIE published a report which
examined 62 studies of lighting and road
accidents from 15 countries.
109
These sug-
gested new or improved lighting led to acci-
dent reductions after dark in the range of
13% to 75%, although only approximately
one-third demonstrated statistical signifi-
cance. One interesting point is that they
found ‘No definitive relationship between acci-
dent reduction and parameters of lighting’.
The 2009 Cochrane Collaboration
review
110
of road lighting and traffic accidents
identified 17 controlled before-after studies,
including the Box study described above,
conducted in the USA, UK, Germany and
Australia and published from 1948 to 2006.
There are fewer studies here than in the CIE
review because Cochrane reviews apply
strict inclusion criteria. Of the 17 studies,
12 investigated the effects of newly installed
street lighting, four investigated the effects
of improved lighting, and one study
investigated both new and improved lighting.
Effectiveness of lighting was determined using
a rate ratio of accidents before and after the
change to lighting compared with the corres-
ponding ratio in a control area. The review
found, for example, that installing road
lighting in a previously unlit road led to a
rate ratio of 0.45 (95% confidence interval
0.29 to 0.69), which implies a 55% reduc-
tion in crashes compared to that in the
control area.
Advances in technology mean it is now
much easier to collect and analyse larger data
samples and that can be seen in more recent
studies. For example, Wanvik considered
763,000 injury accidents on Dutch roads
over a 20-year period (1987–2006).
24
The
analysis used an odds ratio approach, com-
paring lit and unlit roads in daylight and after
dark, and determined that on lit roads injury
accidents after dark were reduced by 50%.
This agrees well with the 55% reduction
found in the Cochrane review. Within these
data, it can be seen that the benefit of road
lighting is reduced during adverse weather
and poor road surface conditions and that
there is a larger benefit for pedestrians and
cyclists than occupants of motorised vehicles.
Yannis et al.
25
considered 358,485 police-
recorded road accidents in Greece, 1996 to
2008, and also found that on lit roads, there
were fewer accidents than on unlit roads. One
study used night/day crash ratios to investi-
gate effects of lighting on crash frequency for
a specific part of the road – intersections.
111
They examined 22,058 accidents at 6464
intersections in one US state (Minnesota)
over a 4-year period (1999–2002). Lit inter-
sections were associated with a 12% lower
night/day crash ratio than unlit intersections.
Comparing accident rates between lit and
unlit roads tells us nothing about the influ-
ence of changes in light level or other char-
acteristics, and to do that a large number of
sites with different light levels are needed –
this was the approach used in the USA by
Box (Figure 1).
14
Using large datasets help to
overcome limitations of a road accident
approach to establishing light levels asso-
ciated with events being infrequent and
having multiple causation factors.
100
A similar study was carried out in the
UK.
112,113
Data were collected from 89 two-
way urban roads, each at least 1 km long, and
with a 30 mph speed limit, within a 3-year
period (1974–1977). The photometric meas-
urements and the accidents analysed were
only those for dry conditions. Average road
surface luminance was found to be the best
predictor of the night/day accident ratio, and
the best-fit trend suggests an increase in
luminance from 0.5 to 1.0 cd/m
2
reduces the
night/day ratio from approximately 0.57 to
0.42, a 15% reduction in accidents at night
(Figure 3). This increase in luminance is
approximately equal to an increase from 0.7
to 1.4 foot candles (assuming a diffuse road
surface reflectance of 20%), for which the
Box data (Figure 1) suggest a reduction in
accidents at night of approximately 3% for
Road lighting for drivers and pedestrians 169
Lighting Res. Technol. 2018; 50: 154–186
the six-lane roads but an increase of over
100% for the four-lane roads. One reason for
the differences is the speed limit, being lower
in the roads examined by Scott
112
but is also
likely to be affected by factors such as road
geometry and traffic volume.
Jacket and Frith
26
examined 7944 crashes
across 270 km of road in New Zealand in the
period 2006 to 2010. This analysis used night/
day crash ratios to determine the effect of
changes in lighting, lighting being measured
in the field. They found a 19% reduction in
after-dark crashes (across all types of
reported accident) for each 0.5 cd/m
2
increase
in average luminance, a similar reduction to
that reported by Hargroves and Scott.
113
The
reduction varied with context, ranging from
15% for crashes on wet roads to 56% for
midblock collisions with pedestrians.
Gibbons et al.
15
examined 83 000 crashes in
the period 2007 to 2012 over 2000 miles of
road in the USA, with the lighting being
measured across the whole of these roads.
This work used the night to day crash rate
ratio (number of crashes per million vehicle
miles during the night/number of crashes per
million vehicle miles during the day) to
determine the relationship between light
level and safety. The results suggest that
increased illuminance leads to a reduction in
the night/day crash ratio, this relationship
changing for different types of road, but that
at some point, an illuminance is reached
beyond which further increase in illuminance
is unlikely to bring further benefit in terms of
safety: This point identifies the optimum
illuminance. For freeways, this optimum was
5.0 lux. This is lower than illuminances deter-
mined (assuming road reflectance class R2
with q
0
¼0.07) from the recommendations of
IESNA
4
(9 lux) and CIE
1
(21 lux for class
M2). That the optimum light level from
Gibbons et al. for a freeway is significantly
less than current recommendations indicates
Night/day
accident ratio
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
0 0.2 0.4 0.6 0.8
Aver
g
e road surface luminance (cd/m2)
1.0 1.2 1.4 1.6 1.8 2.0
Figure 3 Night/day accident ratio plotted against average road surface luminance. The curve is the best-fitting
exponential through the data after weighting each ratio for the number of accidents to which it relates (after Hargroves
and Scott
113
)
170 S Fotios and R Gibbons
Lighting Res. Technol. 2018; 50: 154–186
an opportunity to reduce light levels on this
class of road by around 50% without
increasing the night/day crash ratio.
Comparison of results or recommendations
is not always straightforward because of
differences in approaches to specifying con-
text. CIE guidance defines context by user
(driver or pedestrian) and within each of these
a lighting class is selected using a series of
criteria that have been determined to be
related to safety such as vehicle speed, traffic
volume and presence of parked vehicles
(Table 6). The IESNA system relates lighting
recommendations to road type (Tables 2 and
3) and does not consider these other criteria.
Many studies
14,15,26,113
use the ratio of
nighttime to daytime road accidents as the
measure of effectiveness of changes in lighting
– better lighting reduces the night/day crash
ratio. Using this ratio, however, involves
making an implicit assumption that changes
in traffic densities, level of alcohol intoxica-
tion, level of driver fatigue and driver demo-
graphics from day to night are the same for
roads lit to different levels and this may not
be correct.
114
One approach to controlling these differ-
ences is to take advantage of the clock change
associated with Daylight Savings Transition
(DST). Typically, adjustment to DST means
that the clock is advanced by one hour in
spring and set back by one hour in autumn.
The effect of this change is that a certain
period of time, close to either dawn or dusk, is
suddenly changed from daylight to darkness
(or vice versa), whilst the traffic density, level
of alcohol intoxication, level of driver fatigue
and driver demographics are unlikely to have
changed. Any change in accident rates in
these periods, before and after the clock
change, can plausibly be ascribed to the
change in ambient light.
Sullivan and Flannagan adopted this
approach to investigate fatal road acci-
dents.
115
They compared crash rates (1987
to 1997) across the USA occurring in the
weeks before and after the Spring and
Autumn DST clock changes. While this
study did not examine changes in the level
of road lighting, it does provide some evi-
dence of the types of road accident that are
likely to be prevented by light. Specifically,
collisions involving pedestrians were found to
be up to seven times more likely in darkness
than during daytime, the risk being greater
for collisions on straight, high speed rural
roads than at intersections. In contrast,
crashes involving a single vehicle were only
marginally more likely in darkness.
The DST approach employs clock change
to establish a period of time in which
accidents may be attributed to changes in
ambient light rather than to other causes.
There are limitations of this approach, for
example, the use of a single hour of the day
reduces the sample size, and the change
in light may be confounded by changes in
transport choice
116
and seasonal variation in
weather and road surface conditions.
Johansson et al.
117
used an alternative
approach, identifying a case hour that was
in either darkness or daylight according to
seasonal variation in sunrise and sunset times.
Data from the whole year can be considered.
To account for other seasonal variations, an
odds ratio approach was used, meaning that
dark/day changes in the case hour were
compared against contemporary changes in
a control hour. They used this method to
analyse three sets of accident data (Sweden,
1997–2006; Norway, 1996–2005; the
Netherlands, 1987–2006). Table 10 shows
the odd ratios pooled across these three data
sets, for urban and rural roads. Note that an
odds ratio of 1.0 indicates the same risk of
accident in darkness as in daylight. These
data suggest a more modest increased risk of
accident after dark than the seven-fold
increase reported by Sullivan and
Flannagan.
115
Inadequate lighting is not the only cause of
road accidents. It was concluded by CIE that
Road lighting for drivers and pedestrians 171
Lighting Res. Technol. 2018; 50: 154–186
the installation of lighting cannot be expected
to result in a reduction in accidents if there is a
major non-vision problem at any particular
site’.
109
The assumed association between
lighting and accidents can lead to pressure
being applied to a local authority to install
lighting in response to an accident without it
being certain that the underlying cause was
lack of lighting: this may prevent resources
from being diverted to where they will be
most effective.
118
A further caveat to the accident frequency
approach is that driving performance can be
hindered by distraction
119–121
and this has
been identified as a significant cause of road
accidents.
122,123
Drivers are less responsive to
hazards when distracted by actions such as
using a mobile phone, which can cause a
greater distraction, and significantly slower
reaction times, than that associated with the
legal limit for blood alcohol level.
124
4.4. Comparing approaches
Research undertaken to establish the bene-
fits of road lighting for drivers can be divided
into three broad types: effects on visual
function measured in the laboratory, driving
performance on simulators or test tracks and
the frequency and type or road traffic colli-
sions. Either of these approaches could be
used to set road lighting standards. In some
cases, standards have migrated between dif-
ferent approaches; for example, the IESNA
first set a light level based on crash data
(the Box data),
125
then tried to move to a
vision-based system (STV approach),
30
and
has since returned to the original accident-
based format.
4
These documents had some
internal inconsistencies, but ultimately, the
approaches have shown similar light levels to
be selected with some slight variation based
on roadway type with some roadways assum-
ing they need a higher level than they do when
crash data are reviewed. As an example, the
illuminance criteria for Freeway Class A of
6.0 lux became 0.6 cd/m
2
for an R1 road class.
An advantage of the vision-based approach
is the direct link between the independent
(changes in lighting) and dependent (visual
response) variables. If vision was the only
factor influencing driving performance and
traffic collisions, then all three approaches
would reveal similar relationships with light-
ing, but that is not the case.
126
Laboratory
studies and simulators or test tracks tend to
adopt a metric of interest (e.g. detection
distance) to determine the effect of changes
in lighting, with the assumption that this is
directly related to safety. Driving perform-
ance is also influenced by fatigue, alcohol
consumption and cognitive distraction, which
change the relationship between lighting and
performance. If the primary target of road
lighting is to promote safe travel along a road,
then standards should be guided by collision-
based analyses. However, these demand more
research effort than vision-based analyses due
to the rarity of roadway crashes and the
independent archiving of lighting data and
accident data. In the meantime, research
linking lighting to driver visual performance
and behaviour must be used to determine
light levels.
New lighting design approaches and
research has shown then we can modify
behaviours with the roadway lighting, which
allows us to determine lighting needs in
specific areas of the roadway.
107
This will
ultimately determine the best approach to
lighting a roadway with the maximal benefit
to the driver.
Table 10 Odds ratio of accident risk in darkness
Road user Odds ratio of accident risk
Urban Rural
Pedestrians 2.08 2.29
Cyclists 1.52 2.37
Car occupants 0.94 1.21
Note: Data are the pooled estimate of accidents in
Sweden, Norway and the Netherlands, after Johansson
et al.
117
172 S Fotios and R Gibbons
Lighting Res. Technol. 2018; 50: 154–186
5. Lighting for pedestrians
5.1. The visual needs of pedestrians
In 1950, Waldram stated that ‘‘probably the
most important problem to be solved is the
lighting of residential roads ... The methods
used hitherto have generally been small-scale
imitations of traffic route methods and have
achieved the worst of both worlds: there is
room for some careful experiment and a new
approach in this field.’’
6
The foundations of
lighting for pedestrians were set by Caminada
and van Bommel.
40
Prior to this point,
lighting research related to pedestrians had
largely considered only their visibility to
drivers
127–129
rather than addressing the
direct needs of pedestrians. From a common
sense approach, Caminada and van Bommel
suggested three key criteria to be detection of
obstacles, identification of persons and pleas-
antness. Some verification of the likely
importance of the first two of these criteria
was gained using mobile eye tracking in a
natural, outdoor urban setting.
76–77
Eye
tracking reveals those locations on which
gaze is directed but without revealing the
attention being paid to that object of view:
what this work did was use a dual task
(additional cognitive load) to reveal the more
important of these visual fixations.
One issue not raised by Caminada and van
Bommel was the contribution of lighting to
promote reassurance to walk after dark, in
other words, to increase the level of perceived
safety or reduce the fear of crime. Directly
asking people as to whether lighting makes
them feel safer may lead the witness toward
the desired answer regardless of whether it
was the intended response. The benefit of
road lighting was however demonstrated in a
study using an unfocussed approach that
aimed deliberately to reduce the focus on
lighting or fear.
130
This was to ask people to
provide photographs of locations where they
would and would not be happy to walk alone,
after dark and then use these images as visual
prompts in a subsequent interview where they
were asked to explain their choices of loca-
tions. The presence of road lighting featured
in a similar proportion of responses as did
access to help and the physical features of an
environment associated with prospect and
refuge, and these more than any other factors.
The importance of light was also confirmed
by others.
131
Locations that are considered to be
brighter tend to be associated with higher
levels of reassurance
132,133
and brightness is
influenced by both the level and SPD of
lighting. Regarding the benefit of light level,
studies examining two or more illuminances
tend to find the higher illuminance to provide
the safer environment,
35,134
regardless of
whether the illuminances observed were rela-
tively low (0.24 lux and 1.31 lux),
135
or rela-
tively high (15 lux, 25 lux and 50 lux).
136
In
some studies, responses are sought before and
after a change to the lighting, with that
change tending to be an increased light level
and/or a whiter SPD, and these tend to find a
favourable response to the change – greater
reassurance. What we do not know, however,
is whether the favourable response was due to
a change per se, a Hawthorne-like response
where any change would have led to greater
reassurance, or because of the actual changes
in lighting conditions.
Two studies reveal directions that might
provide resolution. First, consider the field
survey reported by Knight,
137
which was
largely designed to demonstrate that MH
lighting would be considered safer than the
HPS lighting it replaced. Knight also included
a reverse change, in which the MH lighting
was replaced with HPS lighting, and the
results suggest a statistically significant reduc-
tion in the perception of safety (p50.05). This
gives some confirmation that observers were
evaluating the effect of lighting and not just
responding to a change. Second, Boyce et al.
42
introduced the day-dark approach in which
ratings of reassurance are captured both
Road lighting for drivers and pedestrians 173
Lighting Res. Technol. 2018; 50: 154–186
during daytime and after dark, and the
effectiveness of lighting is evaluated against
the difference between the daytime and after
dark ratings. The advantage of this approach
is that it leads towards an optimum illumin-
ance rather than towards ever-higher illumin-
ances. Boyce et al. investigated car parks in
the US and their results suggested an illumin-
ance of 30 lux was required to reduce the
day-dark difference to 0.5 units on their 1–7
response scale. The day-dark method has
since been applied to pedestrian footpaths
and day-dark differences of 0.5 units on the
response scale (1 ¼very dangerous to 6 ¼very
safe) correspond to illuminances of 7.0 lux
(a field study in Sheffield, UK) and 10 lux
(a field study in Rome, Italy).
138
There is evidence that SPD affects bright-
ness under the low light levels of road
lighting, this evidence coming from studies
using a range of contexts, procedures and
specific SPDs.
72,137,139–146
These studies tend
to show that an increase of radiant power in
the short-wavelength region enhances spatial
brightness. There is on-going consideration
regarding whether this is best characterised by
the rod receptors or by some combination of
the s-cone receptor and ipRGC,
146,147
and
with the adequacy of horizontal illuminance
as a measure for spatial brightness:
148
Any
proposals need to consider practicality along-
side precision.
One reason for investigating reassurance is
that greater reassurance is assumed to pro-
mote the decision to walk rather than use
motorised transport for local journeys: Foster
et al. found that for every increase of one level
on a five-point Likert scale measure of
perceived safety, the amount of time spent
walking within the neighbourhood increased
by 18 minutes per week.
149
This decision
could be investigated directly by counting
the numbers of pedestrians walking in differ-
ent lighting conditions but this would require
careful matching of test and control locations
to ensure the only difference was lighting.
In one study,
116
the effect of ambient light
level on travel choice was investigated using
the DST clock-change approach used by
others to investigate road accidents:
115
the
numbers of pedestrians and cyclists during the
case period were significantly higher during
daylight conditions than after-dark, and this
relationship was subsequently confirmed
using a second method of analysis.
150
Road lighting should aid the detection of
pavement obstacles that might otherwise
result in a fall, and the associated research
has focussed on the ability to detect pavement
irregularities such as a raised paving slab.
This is important because falls on public
footpaths are a significant problem in terms
of the number of cases, the severity of the
resulting injury and the national cost.
151–154
Four studies have investigated how changes
in lighting affect obstacle detection in periph-
eral vision, two using a scale model
70,155
and
two studies using larger apparatus to improve
ecological validity
71,156
; a further study inves-
tigated the ability to safely navigate obstacles
following a sudden reduction in light level.
157
Further work sought to identify the critical
height obstacle that pedestrians ought to be
able to detect, rejecting the widely cited (and
apparently unsubstantiated) rule of 25 mm,
and instead suggesting 10 mm to be the
critical height.
158
In all, 10 mm is the approxi-
mate lower quartile of the range of minimum
foot clearance when walking along a flat
surface and the lower limit of the range of
heights associated with the most frequent
number of tripping accident compensation
claims.
Laboratory trials show that while higher
illuminances lead to increased detection prob-
ability, this reaches a ceiling in the region of
2.0 lux; observer age and light source spec-
trum (characterised using the S/P ratio)
affect detection only at low illuminance
(0.2 lux).
70,71,155
Consideration of these results
alongside those of Boyce
157
suggests that a
minimum photopic illuminance of 1.0 lux is
174 S Fotios and R Gibbons
Lighting Res. Technol. 2018; 50: 154–186
sufficient light for pedestrians of all ages to
safely detect and avoid trip hazards under any
type of lamp. Still to be resolved are the
influences of disability glare and the spatial
distribution of light.
Pedestrians make judgements about the
intentions of other people, for example to
inform the decision of whether or not to
continue walking in the same direction or to
take action to avoid approaching any closer.
After dark, road lighting should assist this
judgement. Early work on this topic examined
identity recognition judgements.
41,141,159
One
conclusion drawn from this work was that
lamp spectrum does not influence the per-
formance of the identity task. Other studies,
however, concluded that there is a significant
effect of SPD
137,160
and these data contrib-
uted to an assumed benefit of better colour
quality in revised guidance.
68
Subsequent
research first examined methodology, propos-
ing that different procedures may lead to
different conclusions,
161,162
that facial emo-
tion recognition from expression is a more
suitable task than identify recognition,
163–165
that a brief duration of 500 ms better resem-
bles typical behaviour than does continuous
observation,
166,167
and that the stop-distance
approach used in many studies may not lead
to the same conclusions as evaluations made
at the desirable observation distance of
15 m.
166,167
In studies carried out using
facial emotion recognition, SPD is not sug-
gested to be a critical parameter.
168–171
One
question still to be resolved is whether a
measure of vertical illuminance is needed to
characterise this task or whether it is safe to
assume that horizontal illuminance at the
road surface is sufficient.
Cyclists are another category of vulnerable
road user and their needs have received even
less attention in lighting research than for
pedestrians. Such research is desirable
because cyclists are at high risk of a road
accident,
172
and there are policies in many
countries to promote cycling as a sustainable
travel alternative to motorised vehicles. There
is evidence that changes in practice and policy
would be advantageous,
172
that improve-
ments in the design and location of cycle
lamps could improve safety,
173–175
and that
reflective clothing enhances conspicuity after
dark.
176
Many cyclists appear reluctant, how-
ever, to use these aids to safer cycling, with
on-road surveys in the UK suggesting that
only around 25%–58% of cyclists use both
front and rear lamps.
177–179
5.2. Drivers’ detection of pedestrians
While there is a need to consider what
pedestrians would like to see, a significant
benefit to pedestrians of road lighting is that
it may help to increase their visibility to
drivers and hence reduce the frequency of
road traffic collisions involving pedestrians.
Globally, over 270,000 pedestrians die each
year.
180
Within Europe, approximately 20%
of road fatalities involve pedestrians and
cyclists.
181
In the UK in 2015, there were
186,189 road accident casualties of all seve-
rities, of which 28,869 were killed or seriously
injured (KSI): within this, 408 pedestrians
were killed and 4940 seriously injured.
182
Studies using the DST approach to the
analysis of accident records provide clear
evidence that ambient light offers significant
benefit to a reduction in road collisions
involving pedestrians.
115,126,183
One benefit
of road lighting for pedestrian detection is
that it can offset the reduction in detection
distance brought about by glare from the
headlamps of on-coming vehicles.
184
Regarding the amount of light needed to
detect pedestrians, some evidence may be
gained by considering lighting at pedestrian
crossings. There is however no agreement as
to the optimum light level for pedestrian
crossings nor where to measure it. ANZ
guidance
185
suggest horizontal illuminances
of 16 lux (local roads) or 32 lux (arterial
roads).
Road lighting for drivers and pedestrians 175
Lighting Res. Technol. 2018; 50: 154–186
CIE also recommends horizontal illumin-
ances, with averages of 20 lux in residential
areas and 30 lux in commercial areas.
186
US
guidance
4
suggests instead to use vertical
illuminances (at 1.5 m height), these being
10 lux and 2 lux for areas of high and medium
pedestrian conflict, these data as determined
from test track studies.
187
A limitation of specifying a single value of
illuminance is that it does not account for local
conditions: it may be too low if visual adap-
tation is raised by extraneous local lighting or
by a generally high level of road lighting. In the
UK, TR12 of the Institution of Lighting
Professionals overcomes this by recommend-
ing an illuminance relative to that of the road
in which the crossing is placed, which is itself
chosen partly with consideration to the sur-
rounding environment.
188
Specifically, it sug-
gests horizontal illuminances are 3.5 times
(and vertical illuminances are 2.0 times), the
horizontal illuminance of the road. For aver-
age road illuminances specified in BS5489-
1:2013, these ratios lead to horizontal illumin-
ances from 7.0 lux to 52.5 lux and vertical
illuminances of 4 lux to 30 lux.
5
While this may
be an interesting approach, the basis of the
multiplication factors is unknown.
With conventional overhead lighting, a
pedestrian moves between areas of positive
and negative contrast when using a crossing.
Between these areas, the contrast approaches
zero and the pedestrian is difficult to see. An
alternative solution was reported by Bullough
et al.
189
in which the overhead lighting is
replaced by low level bollards with a vertical,
linear light source, placed just ahead of the
crossing and aimed towards pedestrians on the
crossing. This places the pedestrian in perman-
ent positive contrast by illuminating vertical
surfaces of the pedestrian rather than the road
surface. The results of simulations and field
trials suggested that pedestrian visibility is
increased, glare to drivers is significantly
reduced, and installation costs are reduced.
Other factors than lighting are involved in
the detection of pedestrians. First, consider
expectation: in some circumstances, a driver
does not expect to encounter pedestrians and
this reduces their conspicuity,
190
leading to
the ‘looked but didn’t see’ phenomenon.
Second, pedestrians tend to render themselves
less visible to drivers by wearing dark cloth-
ing; there is a tendency for pedestrians to
over-estimate their visibility to drivers and
under-estimate the benefit of reflective cloth-
ing,
191
and to avoid using devices known to
significantly enhance visibility such as reflect-
ive markings to highlight bio-motion
190
or
active visibility aids.
192
Third, a potentially
significant approach to reducing accident
frequency is to consider legal responsibility
for accident compensation.
193
In the UK, the
victims (e.g. a pedestrian or cyclist) of colli-
sions with cars must seek compensation for
their injuries by proving that the car driver
was at fault (i.e. negligent), causing harm to
the cyclist by failing to uphold a reasonable
standard of driving. An alternative approach
is that of presumed liability, where it is
presumed that the car driver is responsible
for any collisions and must pay 100% of the
compensation for the victim’s personal inju-
ries unless the driver can prove that the victim
was significantly at fault. If drivers are thus
motivated to change the manner in which
they consider the safety of vulnerable road
users, this may benefit road safety regardless
of any change in road lighting.
In recent years, there has been a tendency
(within the UK at least) to switch off or dim
road lighting at certain times of the night as
an energy saving measure. Steinbach et al.
194
examined the impact of these actions on crime
rates and traffic collisions across 62 local
authorities in England and Wales of four
energy saving changes to road lighting; per-
manently switching off, reducing the number
of hours switched on at night (part-night),
reducing the output (dimming) and replacing
176 S Fotios and R Gibbons
Lighting Res. Technol. 2018; 50: 154–186
the widely used (in the UK) sodium lamps for
whiter light sources. Regarding crime, it was
found that neither switching-off nor part-
night strategies affected crime rates, but that
there was weak evidence of a reduction in
crime associated with white light and dim-
ming strategies. Regarding traffic collisions,
the study found no evidence that either
strategy led to an increase: this is somewhat
surprising given the results of other studies
suggesting lighting a previously unlit road
reduces the after dark crash rate,
24,25,109,110,111
and that lower light levels are associated with
increased crash rates.
15,26,113
A further problem with such energy saving
strategies is that we do not know how it will
affect behaviour. In one study, lighting was
initially dimmed (to 20%, 40% or 60%) but
switched to 100% (85 lux) when a test par-
ticipant walked past a motion sensor: walking
speed along a 19 m path was slower in those
trials where lighting was initially dimmed
compared to those in which it was maintained
at full output.
195
6. Moving forward
With pressure being placed on the lighting
industry to make responsible choices to con-
trol the side-effects of road lighting, and with
developments in the science and technology of
lighting and lighting research, there is an
ongoing need for standards to evolve. An
effective standard is one that is related to the
intended benefits for road users – an aid to
vision to be able to travel safely, to feel safe
and to minimise the risk of road collisions.
While there appears to be little, if any,
credible empirical support for light levels
recommended in much current road lighting
guidance, data are emerging that will allow
standards to be better informed by empirical
evidence.
In addition to the quantification of lighting,
there may be a need to change the parameters
that are quantified. For pedestrian lighting,
this may be a measure of vertical illuminance
instead of or in parallel to horizontal illumin-
ance. For drivers, there may be a move away
from standards apparently based on STV
towards alternative models such as Relative
Visual Performance
196
or the Cumulative
Probability Index where the probability of a
driver seeing objects in the roadway can be
used for the analysis of the lighting needs
197
and for determining visibility.
29
Such issues are discussed in technical com-
mittees such as those of Division 4 in the CIE.
Currently, there are active technical commit-
tees considering lighting for drivers (TC4-51),
pedestrians (TC4-52) and the impact of glare
(TC4-33), and working groups considering
lighting for the elderly and cyclists. In North
America, the IESNA Roadway Lighting
Committee is preparing a revision of all of
their standards, trying to link lighting needs
to driver performance.
Declaration of conflicting interests
The authors declared no potential conflicts of
interest with respect to the research, author-
ship, and/or publication of this article.
Funding
The authors disclosed receipt of the following
financial support for the research, authorship,
and/or publication of this article: Gibbons:
Much of the research mentioned in this article
has been performed with the support of
Government Agencies like the US Federal
Highway Administration, local agencies,
lighting companies and other interested par-
ties. Fotios’ contribution to writing this art-
icle was supported by the Engineering and
Physical Sciences Research Council (EPSRC),
grant number EP/M02900X/1.
Road lighting for drivers and pedestrians 177
Lighting Res. Technol. 2018; 50: 154–186
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... The national lighting standards of America, Germany, Japan, and China make the minimum request based on illuminance for indoor public places such as the metro station, which tends to fit the lighting system's requirements rather than refining pedestrian's visual effect [1]. Luminance emphasizes light reaching the viewer's position, and it is the only photometric indicator directly related to visual perception [2]. ...
... Informatica 46 (2022) 129-136 129 luminance ratio of the task area and surrounding area should be maintained in the value of 3, otherwise, there would be visual discomfort or glare. Hence the reasonable value of luminance contrast should be kept in the range of [1,2,3,20]. The static and dynamic luminance contrast levels are shown in Table 2, what needs to be more specifically noticed is the static levels represent the states of luminance contrast, while the dynamic levels represent the extent of luminance contrast, only in the latter the value of luminance contrast makes sense. ...
... It was inferred through scatterplots that part of the reasons might come from abnormal ocular data influences influenced by extreme luminance contrast values. At the measurement level of 8, the luminance contrast value came to 5.02, which was far beyond the reasonable range of [1,2,3]. In brief, the participants' fixation durations on the sign poster decreased as the value of luminance contrast increased. ...
Article
This paper investigated the effect of luminance contrast between sign and surrounding object on the gaze behavior of pedestrian, static or dynamic 360° panorama rendered in a virtual environment applied to simulate the wayfinding of pedestrians in the metro stations. Fifty-five participants observed the sign posters and the advertisement boards with distinct luminance contrasts (31 of them were in static levels, 24 of the rest were in dynamic levels) and were asked to point out the graphic or textual changes in the area after 30s. The eye tracker recorded ocular data, and glare perception was inquired by questionnaire. The result of T-test and Regression analysis revealed that luminance contrast was a saliency feature distinguishing visual targets and surrounding objects. The correlation between the value of luminance contrast and fixations, fixation durations on the sign is negative. Each increase in luminance contrast by one unit reduces the mean of fixations by 0.826, accompanied by a stronger feeling of glare, which indicated the strategic adaption of visual attention. The study contributed to our understanding of a new sight of lighting design in public traffic places and confirmed that lighting simulation in an immersive virtual environment can effectively analyzes visual perception.
... Something simple like dynamic lighting is one of the best usages of instant data. Research on dynamic lighting by (Boyce, et al., 2009), (Fotios & Gibbons, 2018) showed that light intensity of cars and roads based on speed and amount of traffic all measured on real-time cell phone data saves energy and avoid accidents. It is evident that automated decision making on incomplete, inaccurate data is always risky and should be avoided. ...
Thesis
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Becoming truly a data-driven organisation is not a purpose in it itself. However, surviving in this digital dynamic rapidly changing world with potential threats of FINTECH’s and being compliant with SDG, it is not the question ‘if’ but ‘when’ to become data-driven. Supported by data-driven innovation it can speed up the process of delivering disruptive and sustainable new services and monetizing data as an asset. This dissertation describes the vital elements of a data-driven organisation such as data-strategy, data-driven innovation, data analytics, decision making with data and the cultural aspects of such an organisation referring to actual academic literature of Anderson, Curley, Marr, Moesgaard Andersen, Treder and research by acclaimed organisations such as AFM, OECD, Capgemini and Gartner. The deductive method was used for the research. The involved interviewees were selected using a Hayes stakeholder analysis. Management level was interviewed regarding the subject of “becoming a leading-edge data-driven organisation and what makes them stay successful”. The results show the current data-driven state of the Dutch Mortgage Industry compared to relevant literature and recommends which steps to undertake to become a collaborative, meaningful, innovative and sustainable leading edge data-driven organisation.
... It is unclear what studies and empirical data were originally used to determine current road lighting uniformity recommendations. In comparison, the recommendations of average luminance and illuminance in standards also appear to lack robust empirical evidence [12]. ...
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Road lighting uniformity is an essential lighting quality parameter for motorists and pedestrians and varies with lighting design parameters. Increased road lighting uniformity may result in benefits, such as increased reassurance and perceived safety for pedestrians or an increased overall visual perception. However, no previous study has investigated how road lighting uniformity varies with lighting design scenarios or how the uniformity of various lighting design scenarios affects other essential parameters, such as energy performance and obtrusive light. This study aimed to investigate: (I) how uniformity varies with different road lighting design scenarios, and (II) how uniformity correlates with energy performance and risk for increasing spill light. The study is limited to pedestrian roads. We performed photometric calculations in ReluxDesktop for more than 1.5 million cases with single-sided pole arrangements and for various geometries of road width, pole distance, pole height, overhang, and luminaire tilt. The results were analyzed with a set of five relevant metrics that were calculated and analyzed together with uniformity. For the evaluation, we used the minimum luminaire power needed to achieve an average illuminance of 10 lx, the power density indicator (DP), edge illuminance ratio (REI), and we introduced two new indicators for spill light on the ground in the border areas: the extended edge illuminance ratio (extended REI) and the spill flux ratio (RSF). The results show that increased uniformity levels may significantly increase energy consumption and spill light, but that both these impacts can be relatively controlled if uniformity is kept under certain limits. The investigated cases also demonstrated that improper lighting planning significantly increases adverse effects, such as spill light.
... Mitigating excessive brightness and glare may lead to several benefits for healthcare, property and security. The benefits of darkness for healthcare includes reduced chances of road accidents by shifting the light adaptation levels of vehicle drivers such that they can easily see details on the roadway or pedestrians crossing the road [30]. The benefits of providing only the minimum required level of lighting for property and security includes reduced chances of criminal and destructive activities like graffiti, theft or vandalism that actually thrive on bright nighttime lighting [31]. ...
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This paper aims to derive a design framework for dovetailing darkness and light while planning outdoor spaces using the concept of pragmatic utopia. Pragmatic utopia is a sustainable design movement characterized by an inclusive outlook towards ecologically, economically, and socially sustainable design. Ideological concepts of pragmatic utopian lighting design derived from literature are presented via their criteria for expanding sustainable lighting. Values of darkness derived from literature are presented via their spatial characteristics and temporal outlook. These ideological lighting concepts are then systematically matched with the darkness values to develop a dark-light design framework that can be used as a guidance tool for analysing and designing outdoor spaces with darkness and light. The applicability of this framework is tested by analysing three popular outdoor lighting projects that have addressed critical issues such as biodiversity protection, darkness preservation, heritage conservation, and social interaction as case studies. The objective is to use this framework for improving the ecological, economical, and socio-cultural fabric of outdoor spaces with carefully planned darkness and lighting.
... We anticipate these results to be a starting point for more sophisticated approaches to shape new light distributions also for many more different scenarios and with additional focus on the far field to realize a safe environment for all traffic participants. Figure 1: Average illuminance of road lighting in the UK in the past, a distinctive increase especially since the 1960s is visible, adopted from [1]. ...
... Research shows that lighting has many benefits for the safety and livability of cities. These benefits are the prevention of road accidents (Fotios & Gibbons, 2018;Uttley et al., 2017;Wanvik, 2009), reduced -fear of-crime Welsh & Farrington, 2008), greater sense of safety , active use of outdoor facilities after dark Pedersen & Johansson, 2018;Rahm et al., 2020), and enhancement of urban spaces (Giordano, 2018;Nasar & Bokharaei, 2017a). Besides these benefits, there are also some concerns related to the negative environmental impact of lighting. ...
Thesis
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North West Europe (NWE) faces a great challenge to cut 80% of greenhouse gas emissions by 2050. To reach this target by 2050, energy efficiency is one of the main instruments defined in the Climate and Energy Roadmap of NWE (Notenboom, 2012). Energy efficiency in cities is one of the biggest challenges for the municipalities that have been struggling recently. According to European Commission (2013), standard public lighting is one of the largest consumption items for municipalities, covering up to 60% of total electricity consumption. Thus, most of the municipalities have been seeking lighting solutions for public spaces considering the environmental, economic, and social impact of lighting. As pointed out by Den Ouden and colleagues (2012), new lighting technologies have been creating a revolution in the lighting industry and urban lighting has been benefiting from this innovation. With the possibilities that LED offers and the integration of smart sensors, new solutions for urban lighting are emerging to reduce energy use by dimming down the streetlights at the right time and place, which is recognized as smart urban lighting. For instance, smart lighting systems can manipulate lighting parameters such as light level that react to external input such as the presence of a pedestrian or cyclist. For this reason, the Smart-Space Project aims to facilitate the uptake of smart urban lighting in small and mid-size municipalities to reduce energy use and CO2 emission while ensuring safety and livability throughout NWE. The Smart-Space Project brings together end-users (cities/citizens) and innovation stakeholders (research institutes, SMEs, enterprises) from the Netherlands, Belgium, France, and Ireland to develop an interoperable smart lighting platform. One of the main goals of the Smart-Space Project is to demonstrate the impact of smart lighting on energy consumption and CO2 reduction while enhancing the safety and livability of public spaces at four pilot cities (Smart Space Project). Thus, the social impact of the project needs to be investigated through the evaluation and monitoring of user experience (UX) at four pilot sites. However, there is not a validated UX evaluation method to be used for smart urban lighting yet. The goal of this PDEng project is to design a toolbox to support municipalities in the evaluation and monitoring of citizen's perspective. This toolbox is entitled the User eXperience Evaluation (UXE) Toolbox. The UXE Toolbox presents 25 tools in five categories (i.e., self-report technique, measuring body signals, information and communication technologies, statistics of official documents, and site observations) to measure 23 sub-parameters under seven parameters (i.e., acceptance, visual performance, visual comfort, perceived safety, attractiveness, liveliness, and safety) in three dimensions (i.e., attitude, perception, and behavior). It provides an excel-based tool, guidelines, and demo cases. Guidelines help municipalities to find relevant parameters and choose suitable tools. Demo cases show how the guidelines work over the use cases co-created within the Smart Space Project.
... 2022, 11, 115 2 of 13 lighting coverage applied in community safety planning activities has effectively eliminated the probability for criminal behavior and reduced the fear of crime [13][14][15][16]. In addition, lamp spot coverage and design material of lighting are also undeniable factors that impact pedestrians' and drivers' visual ability to prevent road accidents [17]. Bullough et al. (2013) combined visual coverage area analysis with a statistical association between lighting and nighttime crashes and demonstrated an improvement in traffic safety where changes in the night to day crash ratio did not exceed 13% [18]. ...
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Improved street lighting can provide better use of public space and helps to promote safety while driving or walking. In terms of balancing benefits and impacts, on the basis of cost saving, this research adopts two prominent mathematical models, the maximal coverage location problem and the location set covering problem, to optimize street light locations. By comparing with the currently installed lights following the rule of thumb, the mathematical models in this research achieve the effect of saving electric energy while meeting residents’ traffic safety needs and living conditions. Furthermore, the models can provide greater coverage of illumination using the same amount of energy.
Thesis
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Immersive virtual reality (IVR) represents one of the most promising technological aids in the development of a functional lighting design, especially when considering different points of view as users’ satisfaction. Nowadays, immersive virtual reality is one of the new technologies with a wide range of applications. In particular, immersive virtual reality can play an important role in the lighting design, thanks to its ability to allow for a quick assessment between different design choices based on spaces, colors and light. However, the IVR has to guarantee a correct reproduction of light behavior from photometric and visual points of view, in order to be effectively used for lighting analysis. The main outcomes can be related to the: i) methodology to use Unreal Engine 4.22 as a tool for lighting applications, allowing correct reproduction of artificial light distribution in the game engine by identifying and properly setting a restricted set of parameters and ii) investigated subjective and objective visual responses and participants' interaction with the virtual environment based on measurements of perceived presence. In case after the download you are interested in the methodology and some results, you are kindly requested to provide these citations: Scorpio, M., Laffi, R., Teimoorzadeh, A., Ciampi, G., Masullo, M., & Sibilio, S. (2022). A calibration methodology for light sources aimed at using immersive virtual reality game engine as a tool for lighting design in buildings. Journal of Building Engineering, 48 doi:10.1016/j.jobe.2022.103998 Scorpio, M., Laffi, R., Teimoorzadeh, A., & Sibilio, S. (2021). Immersive virtual reality as a tool for lighting design: Applications and opportunities. Paper presented at the Journal of Physics: Conference Series, , 2042(1) doi:10.1088/1742-6596/2042/1/012125 Scorpio, M., Laffi, R., Masullo, M., Ciampi, G., Rosato, A., Maffei, L., & Sibilio, S. (2020). Virtual reality for smart urban lighting design: Review, applications and opportunities. Energies, 13(15) doi:10.3390/en13153809
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This paper presents the procedure to evaluate the performance parameters of street light LEDs i.e. color, photometry, and electrical characteristics such as voltage, current, power, and power factor using a standard Sphere Spectroradiometer. The integrating Sphere 1.5 Meter measures total radiant flux (W/nm), from which total Luminous flux and color quantities are obtained at different levels of the supply voltage. There are three street light LEDs tested experimentally with the Spectroradiometer for different voltage levels for flux and power output. The simulated spectrum test reports give values of parameters such as color, photometry, and electrical quantities. At the later stage, the performance of LED is compared with the conventional incandescent lamp. The simulated spectral, as well as experimental results, have shown the superiority of LED street light over an incandescent lamp.
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The aim of this study was to evaluate the effect of lens shape towards the light performance from light-emitting surface (LES) based street light. The other consideration taken into account was the effect of different LES shapes on the light distribution. Three sets of experiments were carried out to figure out the shape of lens as well as the shape of LES suitable to be used in the street light application. Optical characterization was carried out using the Goniophotometer (GO-2000) and Integrating Sphere (PCE-200A). DIALux Evo software was used to perform simulation by taking the ME4A road lighting requirement set by Tenaga Nasional Berhad (TNB) as a benchmarking. In comparison, Lens D possessing short rounded rectangular lens demonstrated a better light performance as compared to long rounded rectangular and triangular lenses, owing to the acquisition of lesser light trespass problems. Besides, a better light performance was demonstrated by square-shaped LES as compared to the round-shaped LES due to the presence of large surface area that was able to distribute light evenly. Detailed investigation was presented.
Technical Report
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The “100-Car Naturalistic Driving Study” is a three-phased effort designed to accomplish three objectives: Phase I, Conduct Test Planning Activities; Phase II, Conduct a Field Test; and Phase III, Prepare for Large-Scale Field Data Collection Effort. This report documents the efforts of Phase II. Project sponsors are the National Highway Traffic Safety Administration (NHTSA) and the Virginia Department of Transportation (VDOT). The 100-Car Naturalistic Driving Study is the first instrumented-vehicle study undertaken with the primary purpose of collecting large-scale, naturalistic driving data. Drivers were given no special instructions, no experimenter was present, and the data collection instrumentation was unobtrusive. In addition, 78 of 100 vehicles were privately owned. The resulting database contains many extreme cases of driving behavior and performance, including severe drowsiness, impairment, judgment error, risk taking, willingness to engage in secondary tasks, aggressive driving, and traffic violations. The data set includes approximately 2,000,000 vehicle miles, almost 43,000 hours of data, 241 primary and secondary drivers, 12 to 13 months of data collection for each vehicle, and data from a highly capable instrumentation system including 5 channels of video and many vehicle state and kinematic sensors. From the data, an “event” database was created, similar in classification structure to an epidemiological crash database, but with video and electronic driver and vehicle performance data. The events are crashes, near-crashes, and other “incidents.” Data is classified by pre-event maneuver, precipitating factor, event type, contributing factors, associative factors, and the avoidance maneuver. Parameters such as vehicle speed, vehicle headway, time-to-collision, and driver reaction time are also recorded. The current project specified ten objectives or goals that would be addressed through the initial analysis of the event database. This report addresses the first 9 of these goals, which include analyses of rear-end events, lane change events, the role of inattention, and the relationship between levels of severity. Goal 10 is a separate report and addresses the implications for a larger-scale data collection effort.
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Many studies have used surveys to investigate the reactions to changes in lighting from people who walk or cycle. An alternative approach is to use objective data, specifically the number of pedestrians and cyclists present under different lighting conditions. Such data have been reported previously using a daylight savings transition approach. This paper presents a different method for analysing the effect of ambient light conditions in which data from the whole year are examined, rather than only the two weeks either side of the biannual daylight savings clock changes. The results confirm that ambient light has a significant impact: For a given time of day, more people walk or cycle when it is daylight than after dark and more people cycle on cycle trails and walk on foot paths after dark when they are lit than when they are unlit. While both methods use an odds ratio approach, which should account for environmental changes other than lighting, the results suggest the daylight savings method of analysis better isolates changes in weather from the effects of ambient light on travel choice than does the whole-year method.
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One of the aims of outdoor lighting in public spaces, such as pathways and subsidiary roads, is to help pedestrians to evaluate the intentions of other people. This paper discusses how a pedestrians' appraisal of another persons' intentions in artificially lit outdoor environments can be studied. We review the visual cues that might be used, and the experimental design with which effects of changes in lighting could be investigated to best resemble the pedestrian experience in artificially lit urban environments. Proposals are made to establish appropriate operationalisation of the identified visual cues, choice of methods and measurements representing critical situations. It is concluded that the intentions of other people should be evaluated using facial emotion recognition; eye-tracking data suggest a tendency to make these observations at an interpersonal distance of 15 m and for a duration of 500 ms. Photographs are considered suitable for evaluating the effect of changes in light level and spectral power distribution. To support investigation of changes in spatial distribution, further investigation is needed with three-dimensional targets. Further data are also required to examine the influence of glare.
Article
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Previous research suggests darkness increases the risk of a collision involving a pedestrian and the severity of any injury suffered. Pedestrian crossings are intended to make it safer to cross the road, but it is not clear whether they are effective at doing this after-dark, compared with during daylight. Biannual clock changes resulting from transitions to and from daylight saving time were used to compare RTCs in the UK during daylight and darkness but at the same time of day, thus controlling for potential influences on RTC numbers not related to the ambient light condition. Odds ratios and regression discontinuity analysis suggested there was a significantly greater risk of a pedestrian RTC at a crossing after-dark than during daylight. Results also suggested the risk of an RTC after-dark was greater at a pedestrian crossing than at a location at least 50m away from a crossing. Whilst these results show the increased danger to pedestrians using a designated crossing after-dark, this increased risk is not due to a lack of lighting at these locations as 98% of RTCs at pedestrian crossings after-dark were lit by road lighting. This raises questions about the adequacy and effectiveness of the lighting used at pedestrian crossings.
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The presence of fog leads to an increase in road traffic accidents. An experiment was carried out using a scale model to investigate how the detection of hazards in peripheral vision was affected by changes in luminance (0.1 cd/m² and 1.0 cd/m² road surface luminance), scotopic/photopic (S/P) ratio (0.65 and 1.40) and fog density (none, thin and thick). Two hazards were used, a road surface obstacle and lane change of another vehicle. Increasing luminance, and reducing from thick to thin fog, led to significant increase in detection rate and a reduction in reaction time, for both types of hazard. The effect of a change in S/P ratio was significant only when measuring detection of the surface obstacle using reaction times, under the thick fog, with an increase in S/P ratio leading to a shorter reaction time.
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This article reports a novel procedure used to investigate whether ambient light conditions affect the number of people who choose to walk or cycle. Pedestrian and cyclist count data were analysed using the biannual daylight-saving clock changes to compare daylight and after-dark conditions whilst keeping seasonal and time-of-day factors constant. Changes in frequencies during a 1-h case period before and after a clock change, when light conditions varied significantly between daylight and darkness, were compared against control periods when the light condition did not change. Odds ratios indicated the numbers of pedestrians and cyclists during the case period were significantly higher during daylight conditions than after-dark, resulting in a 62% increase in pedestrians and a 38% increase in cyclists. These results show the importance of light conditions on the numbers of pedestrian and cyclists, and highlight the potential of road lighting as a policy measure to encourage active travel after-dark.
Technical Report
This project is a complete investigation of the impact of light-source spectrum on driver visual performance. In a series of human factors experiments, the effect of overhead lighting and headlamp spectral power distribution was evaluated with respect to driver detection and recognition of large and small objects and pedestrians. The potential for applying mesopic multiplying factors to roadway lighting