Learning from
Roadway Lighting Research
By
David M. Keith
October 2002
Basic Questions
• What is roadway lighting?
– illumination on roadways for safety
– design criteria: IESNA or AASHTO or ?
– a lighting system made up of components:
• lamps & their associated maintenance
characteristics
• luminaires and their photometric distribution
• mounting: height, overhang, spacing and layout
• Why roadway lighting?
• What can be learned? Inc.
© 2002 Marshall Design,
Why Roadway Lighting?
• Lighting for Public Safety with Public
Money
• Simplest conditions
– flat continuous surface
– repeating cycle, only need a “typical
calculation”
• Complete set of criteria
– average, uniformity and veiling luminance
• Lighting System Marshall Design, Inc.
© 2002
Why Roadway Lighting?
• Lighting for Public Safety with Public
Money
– adequate and appropriate roadway lighting
improves public safety
• what is adequate and appropriate?
• criteria set by IESNA Roadway Lighting
Committee
• and/or AASHTO
• and/or ?
– Public Money - so should be “efficient”
© 2002 Marshall Design, Inc.
Why Roadway Lighting?
• Simplest conditions
– flat continuous surface
• idealized
• likely to be worse in “real life”
– repeating cycle, only need a “typical
calculation”
• calculation conditions specified in IESNA RP-8-
00
• one standard calculation grid layout
• five“luminaire cycles”, before and after the calc.
© 2002 Marshall Design, Inc.
grid
Roadway Typical Layout
five cycles
of luminaires
along straight
level roadway
with defined
calculation
grid per
RP-8-00 © 2002 Marshall Design, Inc.
Why Roadway Lighting?
• Complete set of criteria
– must meet entire set of criteria
simultaneously
– average, uniformity and veiling
luminance/glare
• average & uniformity over the defined
calculation grid
• veiling luminance is the first metric relating to
glare
– details of criteria depend on design method
© 2002 Marshall Design, Inc.
Why Roadway Lighting?
• Lighting System
– system built from many related-but-
independent components including:
• lamps
• luminaires
• poles, mast arms and foundations
• maintenance operations
– complex and contradictory interactions
• interactions of any two are complex enough . . .
© 2002 Marshall Design, Inc.
What can be learned?
• How to do roadway lighting more
effectively
– meet the requirements for adequate lighting
&
– reduce costs by reducing equipment
• initial and operating costs
• less equipment - from lamps to poles &
foundations
• less watts - lower electricity charges
• less maintenance - less service required
© 2002 Marshall Design, Inc.
What can be learned?
• How to do lighting more effectively
– trade-offs
• between competing requirements
• between improvement(s) & system performance
– compare available opportunities for
improvement(s)
– investigate standard practices & “rules-of-
thumb”
– the more similar the lighting, the more valid
... © 2002 Marshall Design, Inc.
Intermediate Questions
• What exactly are
– roadways
– roadway lighting systems?
– roadway lighting design criteria?
• What are appropriate metrics for
evaluating roadway lighting system
performance?
– money
– pole spacing
– unit power density
© 2002 Marshall Design, Inc.
What are roadways?
• Described by IESNA and/or AASHTO
by:
– surface type (asphalt or concrete)
– number of lanes (“traveled way”, no
shoulders)
• road width = number of lanes * width of each
lane
– traffic classification: Local to Major to
Freeway
with surroundings and
• based on relationships Design, Inc.
© 2002 Marshall
What are
Roadway Lighting Systems?
• a “Roadway Lighting System” includes:
– lamps (source type & wattage) and
luminaires
• reflect operation and maintenance
characteristics
• include photometric and electrical
characteristics
– geometry of pattern, spacing, height &
overhang © 2002 Marshall Design, Inc.
Roadway Typical Layout
five cycles
of luminaires
along straight
level roadway
with defined
calculation
grid per
RP-8-00 © 2002 Marshall Design, Inc.
Roadway System Geometry
© 2002 Marshall Design, Inc.
Why Roadway Lighting
Systems?
• NOT limited to evaluating a component's
individual characteristics
– lamp and source - “white light” or “long
life”
– luminaire shape or materials
– photometric distributions or cutoff
categories
• allows comparative evaluation(s) of the
associated costs and benefits from
© 2002 Marshall Design, Inc.
What are Roadway Lighting
Design Criteria?
• American National Standard Practice for
Roadway Lighting
– ANSI/IESNA RP-8-00, revised in 2000
– three separate design methods
• Illuminance
• Luminance
• Small Target Visibility (STV)
• An Informational Guide to Roadway
Lighting
© 2002 Marshall Design, Inc.
Design Methods: Illuminance
• Illuminance method
– classical - 1928
– lighting system alone
• lamp, luminaire and photometry
• system geometry
– one uniformity criterion: average to
minimum
• no constraint on Emax
– now includes veiling luminance criterion
© 2002 from luminance calculation
• constrains Lvmax,Marshall Design, Inc.
Design Methods: Luminance
• Luminance method
– recent - 1983
– roadway and lighting system interaction
• lamp, luminaire and photometry
• system geometry
• roadway surface
– two uniformity criteria
• average to minimum, maximum to minimum
– ”moving observer” & glare calculations
© 2002 Marshall Design, Inc.
Design Methods: STV
• Small Target Visibility method (STV)
– brand new in 2000 document
– unfamiliar and complex metric VL
• uses luminance, both horizontal and vertical
• contrast weighted over entire roadway
• veiling luminance included
– extension of luminance calculations
– radically different design techniques
• is this suitable for optimization?
© 2002 Marshall Design, Inc.
Roadway Lighting Criteria
Classifications Eavg Eavg / Lavg Lavg / Lmax / Lveil /
Roadway Area R3 Emin Lmin Lmin Lavg
(lux) (cd/m2)
Major High 17.0 1.20
Med 13.0 3.0 0.90 3.00 5.0 0.3
Collector Med 9.0 4.0 0.60 3.50 6.0
0.4
Local Med 7.0 6.0 0.50 6.00 10.0 0.4
Source: ANSI/IESNA RP-8-00
all system calculations meet entire set(s)
of criteria – average(s), uniformities &
glare © 2002 Marshall Design, Inc.
Which metrics?
• What are appropriate metrics for
evaluating roadway lighting system
performance?
– Money
• “universal” - covers everything - supposedly
• “bottom line” - it all comes down to “what does it
cost?”
– Spacing of poles and luminaires
• practical and directly related to basic costs
– Unit Power Density (UPD)
• what is unit power density?
© 2002 Marshall Design, Inc.
What is Unit Power Density?
• Unit Power Density (UPD) is
the energy for lighting
--------------------------------
divided by
the area of the roadway
• units: Watts / square foot or Watts / square
meter
(W/ft2) 2002 Marshall Design, Inc.
© (W/m2)
Which metrics?
• UPD is more appropriate than using
Money
– UPD is a less complex, more stable
evaluation
– UPD focuses on lighting system performance
• independent of special or “aesthetic” expenses
• does not reflect specific utility costs
• does not reflect “the cost of money”
– UPD is less specific, more generally useful
to public © 2002 Marshall Design, Inc.
Which metrics?
• UPD is more appropriate than using
Spacing
– spacing definition differs with pattern
– spacing is inversely proportional to costs
while UPD is directly proportional
• 11% increase in spacing = 9% decrease in costs
– includes lamp performance and ballast
losses, reflects technological opportunities
– more universal, useful for comparisons
between alternative systems
© 2002 Marshall Design, Inc.
Which metrics? UPD!
• applies to lighting systems (not components!)
• corresponds in direct proportion to relative
costs in
– energy & pollution
– installation & equipment
– operation & maintenance
• evaluation of relative performance and savings
through comparisons
• less valid comparing different wattages or
sources
– some important aspects of lighting systems not
© 2002 Marshall Design, Inc.
What is Unit Uplight Density?
• Unit Uplight Density (UUD) is
the uplight from lighting
--------------------------------
divided by
the area of the roadway
• units: lumens/square foot or lumens/square
meter
(lms/ft2) Marshall Design, Inc.
© 2002 (lms/m2)
Which metrics? UPD & UUD!
• Unit Uplight Density (UUD) is closely related
to UPD but measures the overall contribution
from the lighting system to light pollution in
terms of “uplight”
– developed from the presentation made to the IESNA
Roadway Lighting Committee by JF Laporte
– “uplight” is the total light going up from:
• the luminaire - all flux above horizontal (from “all”
luminaires)
• the roadway - all flux onto the roadway times the
reflectance of the roadway
• the rest of the world - all downward flux which does not
land on the roadway times the reflectance of “the world”
© 2002 Marshall Design, Inc.
Preliminary Research Scope
• Optimize designs (minimum UPD) over:
– a range of roadways
• local, collector or major classification, 1 to 6
lanes
– a range of design criteria
• depending on optimization software
– a variety of system components
• lamp type - HPS or MH - and wattage
• luminaire photometrics: IESNA cutoff
classifications
© 2002 Marshall Design, Inc.
Optimization
• For each combination of
“photometry & roadway”
– Find the geometry with the maximum
spacing
• spacing is indirectly proportional to UPD
– Over a range of mounting heights
• overhang set to zero, luminaire over edge of
roadway
– Meeting entire set of appropriate criteria
– Result is “optimum” for combination (min.
© 2002 Marshall Design, Inc.
Preliminary Research:
Roadway and Lamp Wattage
Roadway Class
--------------------------------------
-------------------------------
Width Lanes Local Collector Major
(m)
4 1 150 & 250
7 2 150 & 250 150 & 250
10 3 150 & 250 250 & 400
13 4 250 & 400
17 5 250 & 400
20 6 250 & 400
© 2002 Marshall Design, Inc.
Preliminary Research:
Sources
• high pressure sodium (HPS) only
• difference in Light Loss Factor (LLF) - at end
of life!
– probably have one or two luminaires contributing to
point
– 0.7 for HPS
– “could be even lower”
• consistent with the “existing” IESNA document
on Roadway Lighting UPD’s, LEM-6-1987
© 2002 Marshall Design, Inc.
Preliminary Research:
Lamp and Luminaire Data
Lamp Wattage Rated Lumens Input Watts LLF
HPS 150 16,000 166 0.70
250 27,500 295 0.70
400 50,000 460 0.70
© 2002 Marshall Design, Inc.
Preliminary Research:
Photometric Files
Lamp Wattage All FC CO SC
HPS 150 18 2 7 9
250 17 5 6 6
400 38 8 16 14
All 73 20% 40% 40%
© 2002 Marshall Design, Inc.
Cutoff Classifications
• values are relative to lamp lumen rating
• intensity limits in two separate zones!!!
– “just below horizontal” and “anywhere above
horizontal”
FC CO SC
© 2002 Marshall Design, Inc.
UPD Calculation
• UPD =
#Luminaire * (1.15*Watts/luminaire)
-----------------------------------------------------
(LumCycle * #Lanes * Width of each lane)
• #Luminaire = 2 for staggered arrangement
• 1.15 factor to match previous work in
IESNA publication LEM-6-1987
© 2002 Marshall Design, Inc.
UUD Calculation
• UUD =
Uplight + ReflfromRoad + ReflfromOffRoad
---------------------------------------------------------
(LumCycle * #Lanes * Width of each lane)
• Uplight: all “up lumens” (2 luminaires for
staggered)
• ReflfromRoad: 0.07 * lumens onto the roadway
0.18 * “down
• ReflfromOffRoad: 2002 Marshall Design, Inc. lumens” not on
©
Preliminary Research Results
Figure 1: M10S250H & Semi-Cutoff (Samp0021.ies)
8
7
6
Lavg (cd/m2), STV, UUD
5
UUD
4 STV
Lavg
3
2
1
0
0.50 0.60 0.70 0.80 0.90 1.00
UPD (W/sq. m eter)
© 2002 Marshall Design, Inc.
Preliminary Research Results
Figure 2: M10S250H & Cutoff (Samp0069.ies)
8
7
6
Lavg (cd/m2), STV, UUD
5
UUD
4 STV
Lavg
3
2
1
0
0.50 0.60 0.70 0.80 0.90 1.00
UPD (W/sq. m eter)
© 2002 Marshall Design, Inc.
Preliminary Research Results
Figure 3: M10S250H & Full Cutoff (Samp0064.ies)
8
7
6
Lavg (cd/m2), STV, UUD
5
UUD
4 STV
Lavg
3
2
1
0
0.50 0.60 0.70 0.80 0.90 1.00
UPD (W/sq. m eter)
© 2002 Marshall Design, Inc.
Preliminary Research Results
Figure 4: UUD vs UPD (C10S250H)
6.0
5.5
UUD (lumens/sq. meter)
5.0
FC
4.5 CO
SC
4.0
3.5
3.0
0.30 0.40 0.50 0.60 0.70 0.80
UPD (W/sq. meter)
© 2002 Marshall Design, Inc.
Preliminary Research Results
© 2002 Marshall Design, Inc.
Preliminary Research:
Conclusions
• Optimization procedure does work
– reliable for illuminance and luminance
methods
– not reliable for STV
• Optimum spacing does correspond to
optimum UPD - directly proportional
• Semi-cutoff distributions produce lower UPD
values than other distributions
• Significant potential forDesign, Inc.
© 2002 Marshall
savings is evident
Preliminary Research:
Conclusions
• The most effective way to reduce total
system uplight is to minimize the UPD
(maximize the luminaire spacing) for the
particular luminaire
– UUD comparisons between photometric files
are less certain than for the same photometry
• The STV method appears to offer the lowest
UPD, UUD and associated costs among the
three methods
© 2002 Marshall Design, Inc.
Intermediate Research Scope
• Optimize designs (minimum UPD) over:
– an increased range of roadways
– a range of design criteria
• illuminance method, luminance method, or both
– a variety of system components
• lamp type - HPS or MH - and wattage
• luminaire photometrics: IESNA cutoff
classifications
• Compare results and determine next
step(s) © 2002 Marshall Design, Inc.
Intermediate Research:
Roadway and Lamp Wattage
Roadway Class
--------------------------------------
-------------------------------
Width Lanes Local Collector Major
(m)
4 1 150/175 & 250 150/175, 250 & 400
7 2 150/175 & 250 150/175, 250 & 400 250 & 400
10 3 150/175, 250 & 400 250 & 400
13 4 250 & 400
17 5 250 & 400
20 6 250 & 400
© 2002 Marshall Design, Inc.
Intermediate Research:
Sources
• high pressure sodium (HPS) or metal halide
(MH)
• difference in Light Loss Factor (LLF) - at end
of life!
– probably have one or two luminaires contributing to
point
– 0.7 for HPS
– 0.5 for MH
– “both should be even lower”
• difference in lamp life and in maintenance
© 2002 Marshall Design, Inc.
Intermediate Research:
Lamp and Luminaire Data
Lamp Wattage Rated Lumens Input Watts LLF
HPS 150 16,000 166 0.70
250 27,500 295 0.70
400 50,000 460 0.70
MH 175 13,500 210
0.50
250 20,500 295 0.50
400 36,000 455 0.50
© 2002 Marshall Design, Inc.
Intermediate Research:
Photometric Files
Lamp Wattage All FC CO SC NC
HPS 150 67 17 21 14 15
250 70 30 19 14 7
400 97 28 36 21 12
All 234 32% 32% 21% 15%
MH 175 59 25 6 15 13
250 47 27 4 9 7
400 47 20 16 4 7
All 153 47% 17% 18% 18%
All 387 38% 26% 20% 16%
© 2002 Marshall Design, Inc.
UPD vs Avg Luminance:
Collector 2 Lanes 250W
1.2 HPS
1.0
Unit Power Density (W/m 2)
0.8
FC
CO
0.6
SC
NC
0.4
0.2
0.0
0.4 0.6 0.8 1.0 1.2
Average Pavement Luminance (cd/m 2)
© 2002 Marshall Design, Inc.
Comparing Cutoff
Classifications
• for 250W HPS, photometric file
distribution is
Lamp Wattage All FC CO SC NC
HPS 250 70 30 19 14
7
43% 27% 20% 10%
• Best (lowest) UPD values mostly SC or
NC
or Design,
– in “Best 5”, all© SCMarshall NC Inc.
2002
Comparing Design Methods
• Base calculations meet criteria for BOTH
illuminance and luminance methods
– this is the most conservative approach
• recalculate for meeting criteria of either
illuminance method OR luminance method
– different criteria, same optimization
procedure
• compare each luminaire’s performance
under © 2002 Marshall Design, Inc.
UPD by Design Method:
Collector 2 Lanes 250W
1.8 HPS
1.6
1.4
Unit Power Density (W/m )
2
1.2
1.0 Both
Illum
0.8 Lumin
0.6
0.4
0.2
0.0
S C S S N S S S S C C S N N C S F S C C N N C C F F F F F F F F F
© 2002 Marshall Design, Inc.
Comparing Design Methods:
Collector 2 Lanes 250W HPS
UPD (W/m2)
#Avgd Base Illum Lum %Decr to
Lum
Best 1 0.56 0.56 0.40 -29%
Best 3 0.57 0.57 0.41 -28%
Best 5 0.58 0.57 0.43 -24%
Best 10 0.59 0.59 0.46 -23%
© 2002 Marshall Design, Inc.
UPD by Design Method:
Collector 2 Lanes 250W MH
1.8
1.6
1.4
Unit Power Density (W/m )
2
1.2
1.0 Both
Illum
0.8 Lumin
0.6
0.4
0.2
0.0
S S N N N N S S N F N N F S S F F F F S F F F C F C C C
© 2002 Marshall Design, Inc.
Comparing Design Methods:
Collector 2 Lanes 250W MH
UPD (W/m2)
#Avgd Base Illum Lum %Decr to
Lum
Best 1 0.85 0.85 0.46 -46%
Best 3 0.86 0.86 0.55 -36%
Best 5 0.86 0.86 0.60 -31%
Best 10 0.91 0.89 0.66 -27%
© 2002 Marshall Design, Inc.
% Increase (Base, any Wattage)
in UPD for “Full Cutoff Required”
Road Local Collector Major
#Lanes 1L 2L 1L 2L 3L 1L 2L
3L
HPS
Best 5 20% 17% 15% 17% 18% 12% 14% 15%
Best 10 30% 28% 27% 28% 18% 17% 18%
16%
MH
Best 5 19% 19% 18% 22% 20% 13% 14% 12%
Best 10 21% 22% 20% 22% 24% 16% 15%
© 2002 Marshall Design, Inc.
Intermediate Research:
Conclusions
• Low wattage corresponds to low UPD
values
• Best MH UPD is 1.5 to 1.8 times best HPS
– for similar roadways and wattages
• Lower UPD values correspond to
luminaire distributions with less stringent
cutoff
• UPD for Illum. method similar to Base
Case © 2002 Marshall Design, Inc.
Advanced Research Scope
• Optimize designs (minimum UPD) over:
– some Major High classification roadways
– more luminance runs to match base case data
– a much greater variety of system
characteristics
• MH Pulse Start: revise Rated Lamp Lumens
• Light Loss Factor: use 0.50 for some HPS runs
• OH <= 0: luminaires not allowed over the roadway
• groups shown as Top5 of All dist. or FC
only © 2002 Marshall Design, Inc.
Advanced Research:
Roadway and Lamp Wattage
Roadway Class
--------------------------------------
-------------------------------
Width Lanes Local Collector Major: Med &
High
(m)
4 1 150/175 & 250 150/175, 250 & 400 250 & 400
7 2 150/175 & 250 150/175, 250 & 400 250 & 400
10 3 150/175, 250 & 400 250 & 400
13 4 250 & 400
17 5 250 & 400
20 6 250 & 400
© 2002 Marshall Design, Inc.
Advanced Research:
Lamp and Luminaire Data
Lamp Wattage Rated Lumens Input Watts LLF
HPS 150 16,000 166 0.70
250 27,500 295 0.70
400 50,000 460 0.70
MHP 175 17,500 210 0.50
250 21,500 295 0.50
400 44,000 455 0.50
© 2002 Marshall Design, Inc.
UPD vs Avg Luminance:
Collector 2 Lanes 250W MHP
1.2
1.0
Unit Power Density (W/m 2)
0.8
FC
CO
0.6
SC
NC
0.4
0.2
0.0
0.4 0.6 0.8 1.0 1.2
Average Pavement Luminance (cd/m 2)
© 2002 Marshall Design, Inc.
Comparing Cutoff
Classifications
• for 250W MH, photometric file
distribution is
Lamp Wattage All FC CO SC NC
MH 250 47 27 4 9
7
57% 9% 19% 15%
• Best (lowest) UPD values mostly SC or
NC
or Design,
– in “Best 5”, all© SCMarshall NC Inc.
2002
UPD vs Avg Luminance:
Collector 2 Lanes 250W
1.2 HPS
1.0
Unit Power Density (W/m 2)
0.8
FC
CO
0.6
SC
NC
0.4
0.2
0.0
0.4 0.6 0.8 1.0 1.2
Average Pavement Luminance (cd/m 2)
© 2002 Marshall Design, Inc.
UPD vs Avg Luminance:
Collector 2 Lanes 250W MHP
1.2
1.0
Unit Power Density (W/m 2)
0.8
FC
CO
0.6
SC
NC
0.4
0.2
0.0
0.4 0.6 0.8 1.0 1.2
Average Pavement Luminance (cd/m 2)
© 2002 Marshall Design, Inc.
Comparing Sources:
HPS vs MHP
UPD (W/m2)
#Averaged HPS MHP %Incr to
MHP
Best 1 0.56 0.85 51%
Best 3 0.57 0.86 50%
Best 5 0.58 0.86 50%
Best 10 0.59 0.91
54%
© 2002 Marshall Design, Inc.
Comparing Lamp Output
• corresponds to the product of:
– Light Loss Factor (dependent on
maintenance)
– Rated Lumens (dependent on lamp
technology)
• for one lane roads with HPS luminaires,
make
separate calculations for LLF of 0.50 or
0.70
© 2002 Marshall Design, Inc.
Comparing Overhang Limits
• overhang may be restricted by utility or
jurisdiction (it’s a maintenance safety
issue)
• recalculate all 250W HPS and MHP for
overhang <= zero (Oh<=0)
– allow setbacks, but no luminaires over
roadway
• typically no effect or increase UPD up to
15% © 2002 Marshall Design, Inc.
Comparing Uplight
• with the “best six” luminaires
– from 400W MHP on 4 lane Major road
– two FC, two CO and two NC
– all have full spherical photometric data
• evaluate Unit Power Density (UPD) and
Unit Uplight Density (UUD) for each
luminaire
– does more cutoff correspond to less uplight?
– does system efficiency (UPD) correspond to
uplight? © 2002 Marshall Design, Inc.
UPD vs Avg Luminance:
Major 4 Lanes 400W MHP
1.2
1.0
Unit Power Density (W/m 2)
0.8
FC
CO
0.6
SC
NC
0.4
0.2
0.0
0.4 0.6 0.8 1.0 1.2
Average Pavement Luminance (cd/m 2)
© 2002 Marshall Design, Inc.
Comparing UPD and UUD
Base UPD Base UUD
(W/m2) (lms/m2)
FC 0.78 3.8
FC 0.78 4.9
CO 0.73 5.2
CO 0.74 4.2
NC 0.74 4.0
NC 0.73 3.9
© 2002 Marshall Design, Inc.
Comparing Uplight
• with the “best six” luminaires
• evaluate UPD and UUD for each
luminaire
• revise conditions
– for overhang <= 0 (luminaire not over
roadway)
– for Luminance design method
– for Small Target Visibility (STV) design
method
© 2002 Marshall Design, Inc.
Comparing Uplight: UPD
1.0
0.9
0.8
Unit Power Density (W/m2)
0.7
0.6 Oh <=0
Base
0.5
Lum
0.4 STV
0.3
0.2
0.1
0.0
FC FC CO CO NC NC
© 2002 Marshall Design, Inc.
Comparing Uplight: UUD
6.0
Unit Uplight Density (lumens/m2)
5.0
4.0
Oh <=0
Base
3.0
Lum
STV
2.0
1.0
0.0
FC FC CO CO NC NC
© 2002 Marshall Design, Inc.
Comparing Uplight
• more stringent cutoff (FC or CO) does
not necessarily correspond to less
uplight
• as UPD increases, UUD increases
• as UPD decreases, UUD decreases
• changes in UUD are nearly (but not
always) proportional to changes in UPD
• more efficient lighting system (lower
UPD) does correspond to less uplight
© 2002 Marshall Design, Inc.
Advanced Research:
Conclusions
• The restriction of "overhang less than or
equal to zero" makes little if any change to
UPD values. As the width of the roadway
increases, the change in UPD increases.
• The luminance method offers consistent and
significant reductions in UPD compared to
the base case. The reduction in UPD
becomes smaller as the width of the roadway
increases.
© 2002 Marshall Design, Inc.
Advanced Research:
Conclusions
• For change in rated lumen or LLF values, the
percentage decrease in UPD is only one-half
to three-quarters of the increase in the
available lumens.
– This is significantly different from the widely held
assumption that increases in maintained lumens
produce "inversely equivalent" decreases in UPD:
a 10% increase (11/10) in maintained lumens
would produce a -9% (10/11) change in UPD
© 2002 Marshall Design, Inc.
Advanced Research:
Conclusions
• The comparison for the change from Major
Medium to Major High shows that conclusions
about the rated lumens and LLF comparisons
apply for even more aspects of lighting
systems. The change in criteria is typically
assumed to correspond to a change in UPD
of equal percentage, but instead the change
in UPD is only one-half to three-quarters of
the change in the average illuminance.
© 2002 Marshall Design, Inc.
Advanced Research:
Conclusions
• The increase in UPD when full cutoff
distributions are required varies as the
conditions vary but appears to be consistent
and substantial. This is particularly true for
narrower roads and the luminance method.
For the lighting systems considered in this
study, requiring full cutoff distributions
corresponds to increases in UPD.
© 2002 Marshall Design, Inc.
% Increase in UPD for FC Only
© 2002 Marshall Design, Inc.
Overall Conclusions
• deltaUPD corresponds strongly to
deltaUUD
• deltaUPD is ~ 1/2 to 1/3 of
deltaLampOutput
• UPD drops up to 25% for Luminance
method
• UPD drops up to 35% for STV method
• systems with lowest UPD values typically
with less
have distributionsMarshall Design, Inc. stringent
© 2002
Overall Conclusions
• There is a substantial potential for
reductions in equipment, costs, energy
use & uplight which correspond to lower
Unit Power Density values for roadway
lighting systems.
• Comparing systems can lead to results
which seem counterintuitive (FC ~ less
efficiency).
• The best use of this work may be for
comparisons with specific UPD values
© proposed
developed from2002 Marshall Design, Inc. roadway
Further Research
• Additional data from existing research
– e.g. mounting heights for “Top10” systems
• Comparisons with proposed designs
– potential for improvements
• Comparisons with other photometric
files
– relative performance
– investigate differences for developing
distributions
preferred photometricDesign, Inc.
© 2002 Marshall
Mounting Height (m)
L0
4s
10
12
14
16
18
6
8
15
0H
C0
4s
15
0H
C1
0s
15
0H
L0
7s
25
0H
C0
7s
25
0H
M
04
s2
50
M H
10
s2
50
M H
17
s2
50
H0 H
7s
25
0H
H1
3s
25
0H
H2
0s
25
0H
C0
7s
40
0H
M
04
© 2002 Marshall Design, Inc.
s4
00
M H
10
s4
00
M H
17
s4
00
H0 H
7s
40
0H
H1
3s
40
0H
H2
0s
40
0H
FC
NC
SC
CO
Average Mtg Ht: Base & HPS
LumDnEff vs UPD: Top5F
Collector 2 Lanes 250W HPS
0.75
0.70
UPD (W/m2)
0.65
FC
CO
SC
0.60 NC
0.55
0.50
65% 70% 75% 80% 85%
Luminaire downward efficiency
© 2002 Marshall Design, Inc.
Project UPD & UUD Evaluation
12
10
(Uplumens/m2 of roadway)
Unit Uplight Density
Prop
8
Rev250
FC 2L
6
SC 2L
FC 3L
4
SC 3L
2
0
0.00 0.20 0.40 0.60 0.80 1.00 1.20 1.40
Unit Power Density
(W/m2 of roadway)
© 2002 Marshall Design, Inc.
Learning from
Roadway Lighting Research
This presentation is available at:
http://resodance.com/ali/presentations.html
Distribution for educational purposes is encouraged!
Please send comments, suggestions, questions or
contributions to:
keithd@resodance.com
© 2002 Marshall Design, Inc.