Learning from Roadway Lighting Research By David M. Keith October 2002

© 2002 Marshall Design, Inc. 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?

© 2002 Marshall Design, Inc. 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 –complex and contradictory interactions

© 2002 Marshall Design, Inc. 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” –goal: adequate performance for minimum costs

© 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. grid “typical” becomes the basis for further calculations

© 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. 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 choice of documents: IESNA or AASHTO or ? different methods lead to different designs

© 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 –reduce energy use & associated pollution thermal, chemical and visual/light

© 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 based on relationships with surroundings and roads –pedestrian classification: Low, Medium or High based on potential for conflict with vehicles

© 2002 Marshall Design, Inc. 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 setback is considered “negative overhang” –design criteria to be met different criteria relate to different lighting systems

© 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 potential improvements and/or restrictions

© 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 –AASHTO 1984 based on ANSI/IESNA RP-8-83

© 2002 Marshall Design, Inc. Design Methods: Illuminance Illuminance method –classical –lighting system alone lamp, luminaire and photometry system geometry –one uniformity criterion: average to minimum no constraint on Emax –now includes veiling luminance criterion constrains Lvmax, from luminance calculation

© 2002 Marshall Design, Inc. Design Methods: Luminance Luminance method –recent –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 / RoadwayArea R3 Emin Lmin Lmin Lavg (lux) (cd/m2) MajorHigh Med CollectorMed LocalMed 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) (W/m2)

© 2002 Marshall Design, Inc. 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 suitable for guidelines, legislation and/or ordinances

© 2002 Marshall Design, Inc. Which metrics? 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 included leads to the metric of Unit Uplight Density (UUD)

© 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) (lms/m2)

© 2002 Marshall Design, Inc. 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” –UUD is the total uplight divided by the same area as UPD

© 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 Compare results and determine next step(s)

© 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. UPD) but may be impractical

© 2002 Marshall Design, Inc. Preliminary Research: Roadway and Lamp Wattage Roadway Class Width Lanes Local Collector Major (m) & & & & & & & & 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

© 2002 Marshall Design, Inc. Preliminary Research: Lamp and Luminaire Data LampWattage Rated Lumens Input Watts LLF HPS 15016, , ,

© 2002 Marshall Design, Inc. Preliminary Research: Photometric Files LampWattageAll FC CO SC HPS All 73 20% 40% 40%

© 2002 Marshall Design, Inc. Cutoff Classifications values are relative to lamp lumen rating intensitytwo separate zones!!!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

© 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 ReflfromOffRoad: 0.18 * “down lumens” not on road

© 2002 Marshall Design, Inc. Preliminary Research Results

© 2002 Marshall Design, Inc. Preliminary Research Results

© 2002 Marshall Design, Inc. Preliminary Research Results

© 2002 Marshall Design, Inc. Preliminary Research Results

© 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 for savings is evident

© 2002 Marshall Design, Inc. 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) /175 & /175, 250 & /175 & /175, 250 & & /175, 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 only represents “conventional” MH –limited information on pulse start available (1999)

© 2002 Marshall Design, Inc. Intermediate Research: Lamp and Luminaire Data LampWattage Rated Lumens Input Watts LLF HPS 15016, , , MH 17513, , ,

© 2002 Marshall Design, Inc. Intermediate Research: Photometric Files LampWattageAll FC CO SCNC HPS All % 32% 21% 15% MH All % 17% 18% 18% All % 26% 20% 16%

© 2002 Marshall Design, Inc. UPD vs Avg Luminance: Collector 2 Lanes 250W HPS

© 2002 Marshall Design, Inc. Comparing Cutoff Classifications for 250W HPS, photometric file distribution is LampWattageAllFCCOSCNC HPS % 27% 20% 10% Best (lowest) UPD values mostly SC or NC –in “Best 5”, all SC or NC –in “Best 10”, one is CO and all others SC or NC –best FC is tied for 13th best (lowest) UPD value

© 2002 Marshall Design, Inc. 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 each single method to Base (BOTH methods)

© 2002 Marshall Design, Inc. UPD by Design Method: Collector 2 Lanes 250W HPS

© 2002 Marshall Design, Inc. Comparing Design Methods: Collector 2 Lanes 250W HPS UPD (W/m2) #Avgd Base Illum Lum %Decr to Lum Best % Best % Best % Best %

© 2002 Marshall Design, Inc. UPD by Design Method: Collector 2 Lanes 250W MH

© 2002 Marshall Design, Inc. Comparing Design Methods: Collector 2 Lanes 250W MH UPD (W/m2) #Avgd Base Illum Lum %Decr to Lum Best % Best % Best % Best %

© 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% 13%

© 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 UPD for Lumin. Method lower than others –less stringent cutoff distributions improve more

© 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 much greater –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 –for comparison purposes

© 2002 Marshall Design, Inc. Advanced Research: Roadway and Lamp Wattage Roadway Class Width Lanes Local Collector Major: Med & High (m) /175 & /175, 250 & & /175 & /175, 250 & & /175, 250 & & & & & 400

© 2002 Marshall Design, Inc. Advanced Research: Lamp and Luminaire Data LampWattage Rated Lumens Input Watts LLF HPS 15016, , , MHP 17517, , ,

© 2002 Marshall Design, Inc. UPD vs Avg Luminance: Collector 2 Lanes 250W MHP

© 2002 Marshall Design, Inc. Comparing Cutoff Classifications for 250W MH, photometric file distribution is LampWattageAllFCCOSCNC MH % 9% 19% 15% Best (lowest) UPD values mostly SC or NC –in “Best 5”, all SC or NC –in “Best 10”, one is FC, others all SC or NC –best FC is 9th best (lowest) UPD value

© 2002 Marshall Design, Inc. UPD vs Avg Luminance: Collector 2 Lanes 250W HPS

© 2002 Marshall Design, Inc. UPD vs Avg Luminance: Collector 2 Lanes 250W MHP

© 2002 Marshall Design, Inc. Comparing Sources: HPS vs MHP UPD (W/m2) #Averaged HPS MHP %Incr to MHP Best % Best % Best % Best %

© 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 –40% LLF increase ~ 16% UPD decrease (3:1) for all MH, replace standard with Pulse-Start –each 2% lumen increase ~ 1% UPD decr. (2:1)

© 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% –may change which files have lowest UPD values increase greater for wider roadways

© 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

© 2002 Marshall Design, Inc. Comparing UPD and UUD Base UPD Base UUD (W/m2) (lms/m2) FC FC CO CO NC NC

© 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 compare trends and UPD-UUD relationship across different conditions

© 2002 Marshall Design, Inc. Comparing Uplight: UPD

© 2002 Marshall Design, Inc. Comparing Uplight: UUD

© 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 have distributions with less stringent cutoff systems using lower wattage have lower UPD

© 2002 Marshall Design, Inc. 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 developed from proposed roadway lighting systems with similar characteristics.

© 2002 Marshall Design, Inc. 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 preferred photometric distributions

© 2002 Marshall Design, Inc. Average Mtg Ht: Base & HPS

© 2002 Marshall Design, Inc. LumDnEff vs UPD: Top5F Collector 2 Lanes 250W HPS

© 2002 Marshall Design, Inc. Project UPD & UUD Evaluation

© 2002 Marshall Design, Inc. Learning from Roadway Lighting Research This presentation is available at: Distribution for educational purposes is encouraged! Please send comments, suggestions, questions or contributions to: