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Learning from Roadway Lighting Research

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

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Learning from Roadway Lighting Research

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  1. Learning fromRoadway Lighting Research By David M. Keith October 2002

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. Roadway Typical Layout five cycles of luminaires along straight level roadway with defined calculation grid per RP-8-00 © 2002 Marshall Design, Inc.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. Roadway Typical Layout five cycles of luminaires along straight level roadway with defined calculation grid per RP-8-00 © 2002 Marshall Design, Inc.

  15. Roadway System Geometry © 2002 Marshall Design, Inc.

  16. 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.

  17. 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.

  18. 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 • constrains Lvmax, from luminance calculation © 2002 Marshall Design, Inc.

  19. 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.

  20. 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.

  21. 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.

  22. 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.

  23. 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.

  24. 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.

  25. 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.

  26. 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.

  27. 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.

  28. 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.

  29. 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.

  30. 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.

  31. 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.

  32. 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.

  33. Preliminary Research:Lamp and Luminaire Data LampWattageRated LumensInput WattsLLF HPS 150 16,000 166 0.70 250 27,500 295 0.70 400 50,000 460 0.70 © 2002 Marshall Design, Inc.

  34. 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.

  35. 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.

  36. 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.

  37. 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.

  38. Preliminary Research Results © 2002 Marshall Design, Inc.

  39. Preliminary Research Results © 2002 Marshall Design, Inc.

  40. Preliminary Research Results © 2002 Marshall Design, Inc.

  41. Preliminary Research Results © 2002 Marshall Design, Inc.

  42. Preliminary Research Results © 2002 Marshall Design, Inc.

  43. 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.

  44. 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.

  45. 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.

  46. 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.

  47. 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.

  48. Intermediate Research:Lamp and Luminaire Data LampWattageRated LumensInput WattsLLF 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.

  49. 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.

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

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