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DRL Induced Glare. An Analytical Study of the Effects o f Peak Luminous Intensity. NHTSA Proposed Rulemaking August 7, 1998. Federal Motor Vehicle Safety Standard 108: Lamps, Reflective Devices and Assoc. Equip. Proposed Rule Change : Reduction in the maximum permitted - PowerPoint PPT Presentation
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DRL Induced GlareAn Analytical Study of the Effects
of Peak Luminous Intensity
NHTSA Proposed RulemakingAugust 7, 1998
Federal Motor Vehicle Safety Standard 108:
Lamps, Reflective Devices and Assoc. Equip.
Proposed Rule Change:
Reduction in the maximum permitted
luminous intensity for vehicle daytime
running lights [DRLs]
Rational for Proposed Rulemaking
400+ complaints re: excessive glare
from U.S. public on file
(N.B. Virtually no complaints in Canada)
“This action is intended to provide the
public with all the conspicuity benefits of
DRL’s while reducing glare”
U.S. DRL Intensity Specification
Current Maximum: 7000 cd
compatible with Canadian specification
compatible with high-beam headlamps
operated at half voltage
34-inch maximum mounting height
(else 3000 cd – rearview mirror glare)
Proposed Maximum: 3000 cd (Phase I)
1500 cd (Phase II)
demonstrated “conspicuity” benefits under
high ambient daytime illumination
(based on “search conspicuity” paradigms)
minimal discomfort glare
(especially re: rearview mirrors)
Modeling the Magnitude of Glare Effects
Disability GlareAdrian & Bhanji (1991) equation
Relative elevation of contrast threshold
Discomfort GlaredeBoer Subjective Rating Scale
Schmidt-Claussen & Bindels (1974) model
Analytic Conditions
(4) DRL Intensities
1500, 3000, 5000, 7000 cd
(Proposed – Current NHTSA Maximum)
(5) Observation Distances
20, 40, 60, 80, 100 m
(6) Driver Light Adaptation States
1, 50, 100, 500, 1000, 5000
(Dark-to-Brightest Summer Day)
Driver Luminance Adaptation States
Adaptation Ambient
Time of Day State Illumination
(cd/m2) (lux)
road at night 5 100
twilight / dawn 250 5000
clear winter day 500-150010,000-30,000
brilliant summer day 5000 85,000+
Luminance (cd/m2) = illumination (lux) * reflectance / p
assumption: average scene reflectance = 0.15
(asphalt road = 0.10, grass = 0.20)
Adrian & Bhanji (1991)Disability Glare Model
Lequivalent = k 2
glare
k
glare is the illumination of the glare source at the eye of the observer (lux)
= 9.05Age (in years)
66.4( )41 +( )
is the angle between the glare source and the observer's line-of-sight (degrees)
where:
( Equation 1 )
Influence of Veiling Luminance(Reduction of Retinal Contrast/Visibility)
Nominal Contrast = Ltarget
– Lbackground
/ Lbackground
Ltarget
+equivalent
Lbackground
L
+equivalent
L( ) +equivalent
Lbackground
L( )-Contrastglare
=
+equivalent
Lbackground
Lbackground
LLtarget
-
=
Effects of Glare upon Contrast Sensitivity(Due to Veiling Luminance)
+equivalent
L
Threshold elevation =
backgroundLL
target -
backgroundL
backgroundL
backgroundLL
target -
(
(
)
)
Threshold elevation = Retinal Contrast without Glare Retinal Contrast with Glare
1% Contrast Elevation Factor
backgroundL ( 0.01 ( ) ) / (
backgroundL equivalentL+ )
0.01
Blackwell (1946) showed that small and mid-size objects in theroadway environment can be detected at a contrast of 1%across a broad range of photopic luminance levels.
The effect of veiling retinal luminance upon this nominaldetection threshold can be estimated as follows:
Glare Illumination:Viewing Distance & DRL Intensity
Disability Glare Drops Rapidlywith Increasing Luminance Adaptation
10001001010
2
4
6
8
10
12
7000500030001000
75-year-olds20m (8.93 degrees)
Luminance Adaptation (cd/m2)
Con
tras
t Thr
esho
ld E
leva
tion
DRL Intensity
Conclusion:
DRLs can cause some “disability” at nighttimebut not betweendusk and dawn.
But…What about“discomfort” glare?
Discomfort Glare
deBoer Subjective Rating Scale
1 Unbearable23 Disturbing45 Just Acceptable67 Satisfactory89 Just Noticable
Schmidt-Claussen & Bindles (1974)Disability Glare Model
deBoer Discomfort
Glare Rating= 5.0 - 2 log
glare
0.003 )(1 + backgroundL0.04
0.46
backgroundL
glare is the illumination of the glare soure at the eye of the observer (lux)
is the angle between the glare source and the observer's line-of-sight (minarc)
is the background adaptation state of the observer (cd/m2)
where:
deBoer Discomfort GlareDRL=1500 cd; Changing Adaptation Level
10080604020001
2
3
4
5
6
7
8 1500 cd
Distance (m)
Dis
com
fort
Gla
re R
atin
g
50 cd/m2100 cd/m2
500 cd/m21000 cd/m2
5000 cd/m2
ComfortDiscomfort
Adaptation LevelDay/Clear Sky
Dusk/Dawn
deBoer Discomfort GlareDRL=3000 cd; Changing Adaptation Level
10080604020001
2
3
4
5
6
7
8 3000 cd
Distance (m)
Dis
com
fort
Gla
re R
atin
g
50 cd/m2100 cd/m2
500 cd/m21000 cd/m2
5000 cd/m2
ComfortDiscomfort
deBoer Discomfort GlareDRL=5000 cd; Changing Adaptation Level
10080604020001
2
3
4
5
6
7
8 5000 cd
Distance (m)
Dis
com
fort
Gla
re R
atin
g
50 cd/m2100 cd/m2
500 cd/m21000 cd/m2
5000 cd/m2
ComfortDiscomfort
deBoer Discomfort GlareDRL=7000 cd; Changing Adaptation Level
10080604020001
2
3
4
5
6
7
8 7000 cd
Distance (m)
Dis
com
fort
Gla
re R
atin
g
50 cd/m2100 cd/m2
500 cd/m21000 cd/m2
5000 cd/m2
ComfortDiscomfort
Saturn Special CaseAlternator Over voltage => 10,000 cd
10080604020001
2
3
4
5
6
7
8 10000 cd
Distance (m)
Dis
com
fort
Gla
re R
atin
g
50 cd/m2100 cd/m2
500 cd/m21000 cd/m2
5000 cd/m2
ComfortDiscomfort
DRL Discomfort Borderlines
1008060402000
Distance (m)
Dis
com
fort
Gla
re R
atin
g
50 cd/m2100 cd/m2
500 cd/m21000 cd/m2
5000 cd/m2
1500 cd3000 cd5000 cd7000 cd
10000 cd
Adaptation State
DRL Intensity
Discomfort
Comfort
European Glare Sensitivity?
1000010001001
2
3
4
5
6
7
8
9
UMTRI (1999)Schmidt-Claussen & Bindels (1974)
DRL Intensity (cd)
deBo
er D
iscom
fort
Rat
ing
DRL Intensity > 2000 cdSmall Gains in Visibility
Large Increases in Discomfort
1000010001001010.0
0.2
0.4
0.6
0.8
1.0
DRL Intensity (cd)
Visi
bilit
y Be
nefit