. .

Section Editor:Nicholas T. Dines

Contributor:

Robert ProuseHM Brandston and Partners Inc.New York, New York

Michael SardinaThe SWAGroup, Inc.Boston, Massachusetts

Alan FujimoriHonolulu, Hawaii

Technical Writer :Kyle D. Brown

Reviewers:

Peter CoxeWilliam Lam AssociatesCambridge, Massachusetts

Kenneth E. BassettSasaki Associates, Inc.

SECTION ~ I

Outdoor Lighting

CONTENTS

1.0 Introduction

1.1 General1.2 Objectives of Outdoor Lighting

2.0 Terminology

3.0 General Design Principles

3.1 OrientationLighting HierarchyClear Lighting Patterns

3.2 IdentificationIntersection ArticulationPlacement of LuminairesDeciding What to Light

3.3 SafetyGlareUnderlighting

3.4 SecurityWalkway LightsSurveillanceVandalism

3.5 Atmosphere and CharacterBackgroundForegroundIllumination of Objects (ShapeAccentuation)Color Perception

4.0 Lamp Characteristics and LightDistribution

4.1 Lamp CharacteristicsIncandescent LampsFluorescent LampsMercury Vapor Lamps (Deluxe White)Induction LampsMetal Halide LampsHigh-Pressure Sodium Lamps'White' High-Pressure Sodium LampsLow-Pressure Sodium Lamps

4.2 Light DistributionHorizontal and Vertical Distribution

Basic Light Distribution PatternsUniformityCutoff

4.3 Categories of Light FixturesLow-Level Landscape LightsIntermediate-Height Landscape LightsParking Lot and Roadway LightsHigh-Mast Lights

4.4 Landscape Lighting EffectsUplightingMoonlightingSilhouette LightingSpotlightingSpreadlightingPathlighting

5.0 Low Voltage Systems

6.0 Recommended Levels of Illumination

References

Time-Saver Standards for Landscape Architecture

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1 .0 INTRODUCTION

1 .1 GeneralThis section includes information useful forsolving site lighting problems . Included aredefinitions of terms associated with light-ing, general design principles, characteris-tics of various lamps, and recommendedlevels of illumination (industry standards)for various landscape uses . The informationincluded here will aid in the process ofspecifying fixtures for particular lightingprojects .

1 .2 Objectives of Outdoor LightingThe purposes of outdoor lighting include :(1) improving the legibility of critical nodes,landmarks, and circulation and activityzones in the landscape ; (2) facilitating thesafe movement of pedestrians and vehicles,promoting a more secure environment, andminimizing the potential for personal harmand damage to property ; and (3) helping toreveal the salient features of a site at adesired intensity of light in order to encour-age nighttime use .

2.0 TERMINOLOGYLumen : A quantitative unit of measure-

ment referring to the total amount of lightenergy emitted by a light source, withoutregard to the direction of its distribution .

Footcandle (fc) : A U .S . unit of measure-ment referring to incident light .Footcandles can be derived from lumens (1fc = 1 lumen/sq . ft .) or candelas (fc =candelas/distance 2 ) .

Lux (Ix) : The International Standard (SI)measure of incident light. It is equal to onelumen uniformly distributed over an area ofone square meter (10.7 Ix = 1 fc) (Figure540-1) .

Candlepower : The unit of intensity of alight source in a specific direction, oftenreferred to as Candela . One candela direct-ed perpendicularly to a surface one footaway generates one footcandle of light .

Illuminance: Incident light, or light strik-ing a surface (Figure 540-2) .

Luminance : Light leaving a surface,whether due to the surface's reflectance, orbecause it is the surface of a light-emittingobject (like a light bulb) . Luminance is themeasurable form of brightness, which is asubjective sensation .

Efficacy : A measure of how efficiently alamp converts electric power (watts) intolight energy (lumens) without regard to the

Figure 540-1 . Lux and footcandlemeasurements .

effectiveness of its illumination . It shouldnot be assumed that a lamp which has highefficacy will give better illumination than aless efficient lamp (Figure 540-3) .

Light depreciation : Lamp output(lumens) will depreciate over its effectivelife . Illumination will be reduced further dueto an accumulation of dirt and grime on thelamp and fixture . Adjustments should bemade to compensate for this depreciationwhen determining the average values ofillumination maintained over time . A main-tenance factor of 50 to 70 percent is com-mon for outdoor applications . New installa-tions are routinely designed to deliver 1-1/2 to 2 times as much illumination asneeded, to sustain this maintained outputover the anticipated life of the lamp .

Color: Two measures used to describethe color characteristics of lamps are (1) theapparent color and (2) the color renderingindex .The apparent color of a light source is

given by the color temperature . Figure540-4 shows various index numbers usedto rank sources on a scale that range fromwarm to cool in appearance . Preference forone or another is a matter of taste and usu-ally varies with the context of the applica-tion and with the illumination level . Warmtones tend to be favored when illuminationis low and cooler tones are preferred underhigh lighting levels .

The color rendering index (CRI) is ameasurement of the degree to which objectcolors are faithfully rendered . This scale

ranges from 0 to 100 and is a reasonableapproximation of color rendering accuracy.CRI is completely independent of whethera light source casts the object in a warm orcool tone . The CRI graph shows the rank-ing of the major outdoor light sources(Figure 540-4) . As a general guideline, aminimum CRI of 50 is suggested to attain areasonably faithful or natural color rendi-tion . Lamps ranked significantly below thisare judged to cause visible distortions toappearance .

Time-Saver Standards for Landscape Architecture

Figure 540-4. Color renderingindex .

Glare: A point or surface of luminancethat is above one's current state of adapta-tion . The human visual system can com-fortably see in light levels ranging fromstarlight to noonday sun, but cannot do soover this entire range at the same time . Weadapt to one limited range or another, andperceive glare as any brightness above ourcurrent state of adaptation . Disability glareimpairs visibility and is primarily a physio-logical phenomenon ; e .g ., the nighttimeglare from an oncoming vehicle's head-lights can momentarily blind a driver's per-ception of the road ahead . Discomfort glaredoes not impair visibility but is primarily apsychological phenomenon or an annoy-ance which may produce fatigue if it con-tinues over an extended period of time .

Cutoff light distribution : A term used inreference to the optical design of some fix-ture types . Proper placement of lamps andthe use of carefully aligned reflectors, caneffectively eliminate intense high-anglelight . Most cutoff designs severely restrictfixture intensities above 75 degrees fromnadir, that is, within 15 degrees of horizon-tal (Figure 540-16) .

Figure 540-6. Lighting patterns.

of road and pathway lights tends toobscure rather than reinforce the directionof circulation and the location of intersec-tions (Figure 540-6) .

MAJOR AND MINOR ROADS ARE DISTINCT, AND PEDESTRIANROUTES DEFINED.

Figure 540-5 . Lighting hierarchy .

3 .0 GENERAL DESIGN PRINCIPLES

3 .1 Orientation

Lighting Hierarchy:

Driver and pedestrian orientation can beaided by providing a hierarchy of lightingeffects that correspond to the differentzones and uses of a site . For instance, sub-tle but recognizable distinctions can bemade between major and minor roads,paths, and use areas by varying the distrib-ution and brightness of the light and byvarying the height, spacing, and color oflamps (Figure 540-5) .

Attaining high levels of illuminationalong circulation routes does not have to bea prime consideration in outdoor lighting. Ifa clear and consistent system is provided,low levels may be adequate for safe circu-lation .

Clear Lighting Patterns :

Clear optical guidance can be providedwith the alignment of light fixtures posi-tioned in consistent, recognizable, andunambiguous patterns . A staggered layout

3.2 Identification

Intersection Articulation:

Intersections, decision points, crossings,bus stops, steps, arrival points, etc ., shouldbe articulated in a manner that signals theirpresence, shape, and nature . The illumina-tion pattern should serve as a visual cue towhat conditions may lie ahead .

Placement of Luminaires:

Spacing, height, and distribution of lumi-naires should avoid foliage shadows, pro-vide uniformity, and vertical surface illumi-nation . High mounting and wide spacing offixtures may result in disruptions to the illu-mination pattern due to tree shadows[Figure 540-7 (top)] . Lower mountingheights and closer spacing between fixtures

ofof

may create a more uniform distributionlight promoting the pedestrian's sensesecurity. [Figure 540-7 (bottom)] .

Deciding What to Light:

In some circumstances, it may be equally asimportant to determine what not to light asto determine what to light (Figure 540-8) .

3 .3 Safety

in addition to poor lighting layout anddesign, glare and underlighting can create

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hazardous conditions for pedestrians andvehicles .

Glare:

Glare is a major inhibitor of good visibilityand can be produced by any scale of lightfixture, including small lens-type step lights(Figure 540-9) .

Glare is more of a problem whenexposed light sources, such as lamps orlenses, can be seen directly . Luminaire loca-tion and mounting height, fixture type, andlamp intensity must be carefully selected tooptimize light distribution and minimizeglare .

Lower mounting lanterns may or maynot have sharp cutoff optics . If high-angleillumination is appropriate in order to illu-minate facades, trees, and otherstreetscape elements, then care must betaken to prevent glare . An outdoor mock-up at night is an excellent technique to usewhen deciding what light distribution pat-tern and intensity to use and whether ornot there will be any likelihood of glare .

High-angled cobra-head types of lensesare a major source of glare when usedalong roadways . Luminaires with sharp cut-offs effectively direct the light into a visual-ly useful and comfortable pattern .

Underlighting:

Underlighting is potentially hazardous ifinsufficient light is provided to protectpedestrians and/or vehicles from potentialinjury and damage . Sufficient light is espe-cially important in areas where heavypedestrian traffic is expected, such as nearparks, ball fields, and other places thatattract crowds of people, or where childrencross streets . Parking areas, access andegress points, loading areas, etc ., shouldhave adequate lighting to help protect dri-vers, pedestrians, and vehicles .

Note that overlighting an area can gen-erate high amounts of glare, which can alsocreate hazardous conditions . A careful bal-ance of light intensities must be achieved .Table 540-3 lists recommended levels ofillumination as stated in the IlluminatingEngineering Society's IES LightingHandbook . Levels of lighting are related totypes of use and other characteristics with-in use areas.

3.4 SecurityDarkness, together with unfamiliar sur-roundings, can incite strong feelings ofinsecurity. To provide a sense of security,possible hiding places and dense shadows

Figure 540-8. What to light and what not to light .

1 . Subtle but recognizable distinctions can be made between major and minor roads,paths, and use areas by varying the distribution and brightness of the light and byvarying the height, spacing, and color of lamps (Figure 540-5) .

2 . Clear lighting patterns reinforce the direction of circulation, delineate intersections,and provide a visual cue to what conditions may lie ahead .

3 . Glare from exposed light sources and underlighting are major safety concerns (Figure540-9) . Luminaire location and mounting height, fixture type, and lamp intensitymust be carefully selected to optimize light distribution and minimize glare .

4 . Security is not necessarily enhanced by increasing illuminance levels on the ground ;consider peripheral lighting, vertical illuminance levels, and good color-renderingsources as well .

5 . Color differentiation, unobtrusive illumination of background spaces, and bright illu-mination of objects of interest are common approaches for articulating landscapecharacter.

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should be minimized by the placement ofappropriate light fixtures .

Walkway Lights:

Walkway lights should have enoughperipheral distribution to illuminate theimmediate surroundings . Vertical light dis-tribution over walkway areas should coveror overlap at a height of 2 100 mm (7 ft) sothat visual recognition of other pedestriansis maintained (Figure 540-10) . When thepedestrian's sense of security is a primaryconsideration, low mounting height withclose spacing and a vertical illuminationpattern may be the most effectiveapproach .

Surveillance :

For surveillance needs, lighting require-ments should permit the detection of suspi-cious movement rather than provide for therecognition of definitive details . For thesame expenditure of light energy, it is oftenmore effective to light backgrounds, there-by generating silhouettes, than to light theforeground (e .g ., lighting the vertical faceof a building instead of its horizontal fore-ground (Figure 540-11) . It is also desirableto highlight entrances and to direct lightingaway from points of surveillance .

Vandalism :

The best way to reduce the vandalism oflight fixtures is to use fixtures that aredurable enough to withstand abuse, or toplace them out of reach . An alternativesolution may be to use hardware that is lessexpensive to replace .

3.5 Atmosphere and CharacterA consistency of design expression can beachieved by identifying the common ele-ments in a landscape that give it character,and then using similar approaches to theirlighting . The clarity with which an object isperceived is influenced by its context .

Background:

Exterior spaces should have a well-definedsense of background . Background spacesshould be illuminated as unobtrusively aspossible to meet the functional needs ofsafe circulation and protecting people andproperty. Whenever possible, these needsshould be accommodated with peripherallighting from the walkways, signage,entrances, and other elements relevant tothe definition of the space .

Foreground:

Foreground spaces or objects may be majorelements and should be treated according-

Time-Saver Standards for Landscape Architectu

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540-6ly . Foreground spaces should utilize locallighting which produces maximum focus,minimum distractions, and no glare .Objects of interest and activities can bebrightly illuminated while the backgroundproduces only minimal distraction .

illumination of Objects (ShapeAccentuation):

The direction of the light source is impor-tant for perception of three-dimensionalobjects . The ability to perceive volumetricform is influenced by the gradient of lightand shadow falling on the object .Uniformly distributed, diffused light resultsin poorly rendered shadows (Figure 540-12) ; one must then rely upon outline andcolor in order to perceive the shape andform of the object . Conversely, a singlepoint source will produce maximum shad-ows but may also minimize the perceptionof details .

Usually, the best way to illuminatestanding objects is with a combination ofboth types of lighting . One source shouldaccentuate shape and form by contrastingthe surface with sharp shadows while theother source provides fill-lighting fordetails .

Color Perception :

Differences in lamplight color are oftenused with great effect in public lighting tocolor code roadways or to clearly delineateone area from another. As the general illu-mination level rises in a given situation,preference usually shifts away from a warmappearance toward the cool range .

Accurate color rendition will aid recogni-tion and improve the perception of outdoorenvironments . This is especially importantat the pedestrian scale, where the colorcontrast of paving and landscape materialsis often subtle .

4.0 LAMP CHARACTERISTICSAND LIGHT DISTRIBUTION

4.1 Lamp Characteristics

Selection of a lamp involves trade-offsbetween lamp size, optical control, efficacy,appearance, color temperature, color rendi-tion, lamp life, costs, and maintenance(Table 540-1) .

Incandescent Lamps:

Incandescent lamps have superior colorrendition and a warm white appearance .The disadvantage of a short lamp life canbe overcome by the use of a rugged trafficsignal lamp rated at 8000 hours nominallife or by undervoltaging the circuits toextend the life . Incandescent lamps havethe lowest efficacy of all the lamps .However, they are inexpensive and thesmall filament permits good optical control .

Fluorescent Lamps:

Although compact shapes are becomingmore widely used, most fluorescent lampsare long and linear, making optical controlvery difficult. They tend to produce glareunless they are well baffled . They have agood color rendition, whitish appearance,and superior life . Although they have goodefficacy, their light output may be severelydiminished by very cold weather.

Induction Lamps:

Induction lamps are relatively new, high-frequency sources that have no filaments orelectrodes, but rather use the electromag-netic spectrum to directly energize a phos-phor coating on the bulb . These lampshave a light quality similar to fluorescent ina 90-115 mm (3 1/2-4 1/2 in) sphericallamp envelope, but with a significantlylonger average rated life (up to 100,000hours), and with almost no sensitivity toambient temperature

Table 540-1 . SUMMARY OF LAMP CHARACTERISTICS

Wattage range, Efficacy, Initial costLamp M(ft) lumen/watt* Average life, hrs Apparent color Color rendering of equipment

Incandescent 3-300 (10-1000) 10-25 750-2000 Warm white Best overall Low

Fluorescent 4.5-64.5 (15-215) 40-80 7500-15,000 Warm to cool white Good Medium

Induction 16 .5-25.5 (55-85) 63-70 100,000 White Very Good High

Mercury vapor (deluxe white) 12-300 (40-1000) 25-60 24,000 Cool white Good Medium

Metal halide 52 .5-450 (175-1500) 65-105 7500-20,000 Cool white Very good Med to High

High-pressure sodium (STP) 10 .5-300 (35-1000) 60-120 - Orange-yellow Poor High

'White' high-pressure sodium 45-75 (150-250) 75-80 - Warm white Very good High

Low-pressure sodium 5.4-54 (18-180) 70-150- - Intense yellow Very poor High

*Includes ballast losses

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Figure 540-13 . Typical photometric chart for roadway, walkway or area lighting. Lux (footcandle) levels displayed are fora mounting height of 3 m (10 ft) . Other mounting heights must factor in the multiplier listed in the table. Once minimum illumina-tion levels are identified, fixture spacing is determined by multiplying the number of corresponding mounting heights by two .

Figure 540-14 . Typical photometric chart for directional lighting: Displayed in lux (footcandles). Illumination levels listed arebased on a typical half 42° aiming angle .

Mercury Vapor Lamps (Deluxe White) :

Mercury vapor (MV) lamps have good effi-cacy, excellent life, and a good cool whitecolor. Strong in the blue-green end of thecolor spectrum, the lamp is popular forfoliage lighting . The cost of the lamp andfixture is the lowest of the high-intensitydischarge (HID) lamps . In general, it has agood combination of characteristics whenno extremes are required .

Metal Halide Lamps :

Metal halide (MH) lamps offer superioroptical control and color rendition . Theirefficacy is substantially better than mercuryvapor lamps but slightly poorer than high-pressure sodium lamps . The light appearscool white and has a shorter life than theother HIDs . The cost falls between that formercury vapor and high-pressure sodiumlamps .

High-Pressure Sodium Lamps:

High-pressure sodium (HPS) lamps haveexcellent efficacy, superior optical control,superior life, and very low maintenance,which accounts for their popularity. Thelight tends to have an orange-yellowappearance and a mediocre color renditionof objects . It rarely enhances foliage colorsbecause of deficiencies at the blue-greenend of the color spectrum . If color is not animportant consideration, this lamp canhave broad application . The initial cost forthe lamp and fixture may be higher than

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Figure 540-15 . Typical photometric chart for directional lighting: Displayed in candela . Maximum candela in this exampleis at 0° (2,200 candlepower) . Conversion to lux (footcandle) can be calculated by the above formula .

for metal halide . HPS lamps and fixtures areavailable in a wide range of sizes .

'white'High-Pressure Sodium Lamps:

These lamps provide excellent color rendi-tion in a warm tone similar to incandescent .Efficacy is sacrificed to obtain improvedcolor. The resulting characteristics are across between metal halide and incandes-cent lamps .

Low-Pressure Sodium Lamps:

Low-pressure sodium (LPS) lamps have thehighest operating efficacy but depreciateconsiderably over their lifetime . A large arctube results in poor optical control, but thelamp does have superior life . The light itselfappears an intense yellow and has verypoor color rendition properties . Colors inthe landscape appear as shades of gray.The costs are comparable to those of high-pressure sodium lamps .

4.2 Light Distribution

Horizontal and Vertical Distribution :

Horizontal illumination is especially impor-tant along the ground plane wherechanges in grade occur. However, a consid-erable portion of the night environment isperceived through direct and silhouettelighting of vertical objects and surfaces .Both patterns should be carefully coordi-nated in developing a successful lightingscheme .

Illumination data for outdoor lightingfixtures are illustrated by the manufactur-ers' photometric charts . These charts illus-trate the actual light patterns and intensitylevels on horizontal and vertical planes .Figure 540-13 illustrates basic photometricdata for walkway, road or area lighting . Lux(footcandle) measurements are given forhorizontal distances based on mountingheight and type of fixture . Spacing is deter-mined by identifying minimum desirablelux (footcandle) levels, and doubling thenumber of mounting height units .

Photometric data for directional lighting,typically used for wall or signage applica-tions, are illustrated by Figure 540-14 . Theaiming angle is commonly specified, andthe fixture type is selected based on dis-tance and illumination requirements .

A third type of photometric chart showsthe distribution of candlepower, or intensi-ty, in various directions, independent ofany specific surface (Figure 540-15). Themaximum value within any given point onthe distribution curve can be convertedinto lux (footcandles) with the formulashown in Figure 540-15 . This chart is occa-sionally used when determining light inten-sity and the angle of distribution for accentlighting (uplighting of trees, floodlighting,etc .) .

Basic Light Distribution Patterns :

Spread and Path Lights: These fixturesproduce circular patterns of light that aresymmetrical around the light center.Whenever fixtures produce a light pattern

Table 540-2. UNIFORMITY RATIOS

Uniformity ratioAverage, lux (fc)

Minimum, lux (fc)

21 .4(2)

10.70)

32 .3 (3)*

10.7 (1)*

43 .0 (4)f

107.6 (10)

Visual description of illuminated field

Just a visible difference in light intensities

The high values of the field are twice as brightas the low values

10 .7(l)'

10 .7(l)

* Average and minimum uniformity ratios usuall recommended for roads .y

Very distinct focal highlights, spotty

i Average and minimum uniformity ratios usually recommended for walkways .

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that is symmetrical, only one half is shown,permitting maximum size and accuracy (seeFigure 540-13) .

Wall or Sign Lights : These fixtures arenearly always used to light vertical surfaces .Therefore, photometrics are presented on avertical plane with the fixture set at an opti-mum distance (which varies per fixture)and backlit from the plane (see Figure 540-14) . For a long wall or sign, the spacingfrom fixture to fixture can be determinedby overlapping curves until the minimumacceptable light level between fixtures isestablished .

Accent Lights : Photometricfor adjustableaccent lights, where the aiming angle anddistance to lighted objects can vary, must beexpressed in terms of the light output fromthe source rather than of the light fallingupon the object . Candlepower is measuredon a typical plane through the fixture and ischarted in curve form (see Figure 540-15) .Conversion to lux (footcandles) can beaccomplished by formula .

Uniformity:

The uniformity of an illuminated field canbe described with a ratio of light intensityvalues in lux (footcandles) . The uniformityratio typically compares the average illumi-nation with the minimum footcandle valueof a particular field . A low ratio appearsmore evenly lit and very uniform . Theopposite is true for a high ratio where thetwo values are wide apart, resulting in afield that has distinct and contrasting val-ues . Refer to Table 540-2 for a generaldescription of different uniformity ratios .

Cutoff:

Many kinds of light fixtures greatly reduceglare by restricting high-angle light to notmore than 75 degrees above nadir (Figure540-16) . The following criteria are the gen-eral industry classifications of degrees ofhigh-angle cutoff :

1 . Noncutoff: unrestricted high-angleillumination .

2 .

Semicutoff : not more than 5 percentof peak intensity radiating above 90degrees and 20 percent of peak inten-sity above 80 degrees .

3 .

Cutoff: not more than 2-1/2 percentof peak intensity radiating above 90degrees and 10 percent of peak inten-sity above 80 degrees .

4.3 Categories of Light Fixtures

Various categories of light fixtures com-monly used in outdoor lighting situationsare described below (Figure 540-17) .

Low-Level Landscape Lights:Typical characteristics include :

1 .

Heights usually less than 1 800 mm (6ft) but sometimes up to 3 000 mm (10ft) .

2 .

Lamps may be incandescent, compactfluorescent, induction, mercury vapor,metal halide, or high-pressure sodium .

3 .

Low-wattage capabilities, with limitedintensities .

4 . Substantial variety, with some sizesand shapes fitting within modules offinish materials (brick, etc .) .

5 . Finite light patterns, with directing

capabilities .6 . Light sources are usually below eye

level, so glare must be controlled .7 . Low maintenance requirements but

high susceptibility to vandalism .

Intermediate-Height Landscape Lights:

Typical characteristics include :1 .

Average heights of 3 000 to 45 000mm (10 to 15 ft) .

2 .

Lamps can be incandescent, compactfluorescent, induction, mercury vapor,metal halide, or high-pressure sodium .

3 . Substantial variety of fixtures andrespective lighting patterns .

4 .

Generally used in or around pedestrianpavements, and considered pedestrianin scale .

5 . Lower fixture mounting heights aresusceptible to vandalism .

Parking Lot and Roadway Lights:

Typical characteristics include :1 .

Average heights of 6 000 to 15 000mm (20 to 50 ft) .

2 . Lamps can be mercury vapor, metalhalide, or high-pressure sodium .

3 .

Used to light streets, parking lots, andrecreational, commercial, and industri-al areas .

High-Mast Lights :

Typical characteristics include :1 .

Average heights of 18 000 to 30 000mm (60 to 100 ft) .

2 .

Lamps can be metal halide or high-pressure sodium .

3 .

Used for large parking lots, highwayinterchanges, and recreational areas .

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4 .

Fixtures must be lowered to be main-tained .

4.4 Landscape Lighting Effects

Six lighting effects most frequently used inoutdoor lighting situations are describedbelow (Figures 540-18 through 540-25) .

Uplighting:

Uplighting for Directional Viewing :When a lighted object can be seen fromone direction only, above-grade accentlights can be used . To prevent glare, fix-tures should be aimed away from observersand, if possible, concealed to keep thelandscape uncluttered (Figure 540-18) .

Uplighting for All-Around Viewing : Ifthe lighted object can be seen from anydirection, then well lights with louversshould be considered (Figure 540-19) . Withnewly planted trees, place uplights as closeas possible to the outside of the root ball .

Placing fixtures midway between trees israrely satisfactory . The light typically missesthe trunk and most foliage . It is particularlyunsuccessful if trees are deciduous, espe-cially during the winter stage .

Moonlighting.

The effect of moonlight filtering throughthe trees is another pleasing outdoor light-ing technique . Up-and-down lighting isused to create this effect, which requiresthat fixtures be carefully placed in trees(Figure 540-20) . Ground lighting is accent-ed by shadows from leaves and branches .

Silhouette Lighting:

Trees and shrubs with interesting branchingstructure can be dramatically expressedwhen silhouetted against a wall or buildingfacade . Such lighting also provides addi-tional security near the building (Figure540-21) .

Spotlighting:

Special objects such as statues, sculpture, orspecimen shrubs can be lighted with well-shielded fixtures using spot lamps (Figure540-22) . By mounting lights overhead intrees or nearby structures, glare and fixturedistraction can be eliminated . If ground-mounted fixtures are used, they should beconcealed with shrubbery .

Spreadlighting:

Spread lights produce circular patterns ofillumination for general area lighting(Figure 540-23) . They are effective forgroundcovers, low shrubs, walks, andsteps . However, to take full advantage ofthe light throw, fixtures should be kept toopen areas so that shrubbery does notrestrict light distribution . The overheadspread light provides additional height andthrow . When used in eating or recreationalareas, several fixtures should be used tosoften shadows while creating a uniformlighting effect .

Pathlfighting:

2 .

3 .

4 .

5 .

A variety of lamp types are commercially available . Selection of a lamp involvestrade-offs between lamp size, optical control, efficacy, appearance, color tempera-ture, color rendition, lamp life, costs, and maintenance (Table 540-1) .Illumination data for lighting fixtures are illustrated by photometric charts providedby the manufacturer . These charts illustrate light patterns on horizontal and verticalplanes (Figures 540-13 through 540-15) .Uniformity of illumination is described by a ratio of light intensity values in lux (foot-candles) . A low ratio appears more evenly lit and uniform, while a high ratio displaysdistinct and contrasting values (Table 540-2) .Light fixtures can be broadly categorized into four main types based on size anddesign purpose : Low-level landscape lights, intermediate-height landscape lights,parking lot and roadway lights, and high-mast lights (Figure 540-17) .Levels of lighting are related to types of use and other characteristics within useareas . Table 540-3 lists recommended levels of illumination .

Path lights are essentially spread lights at alower height (Figures 540-24 and 540-25) .In areas where other landscape lighting isused, a high degree of light shielding isnecessary for path lights . This prevents theglare which inhibits a full view of the sur-rounding landscape .

If no other outdoor lighting is used in theimmediate area, less-shielded path lightsmay be acceptable . These fixtures illumi-nate the path and some of the surroundinglandscape as well, but there remains thepossibility that the glare will be disruptive .

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Table 540-3 . RECOMMENDED LEVELS OF ILLUMINATION

Area/activity Outdoor facilities Lux Footcandles Area/activity Outdoor facilities Lux Footcandles(Ix) (fc) ( Ix) (fc)

Building exterior Local RoadsEntry Commercial areas* 9 0 .9

Active use 50 5 .0 Intermediate areas* 7 0 .6Locked or infrequent use 10 1 .0 Residential areas* 4 0 .4

Vital locations or structures 50 5 0Walkways

Building surrounds 10 1 0 -Along roadside

Building and monuments (floodlighted) Commercial areas* 10 0 .9Bright Surroundings Intermediate areas* 5 0 .5

Light surfaces 150 15 .0 Residential areas* 2 0 .2Medium light surfaces 200 20 .0 Distant from roadside 5 0 .5Medium dark surfaces 300 30 .0 Park walkways 5 0 .5Dark surfaces 500 50 .0 Pedestrian tunnels 20 2 .0

Dark surroundings Pedestrian overpasses 2 0 .2Light surfaces 50 5 .0 Pedestrian stairwaysMedium light surfaces 100 10.0 Light surfaces 200 20.0Medium dark surfaces 150 150 Dark surfaces 500 50.0Dark surfaces 200 200

GardensBikeways General lighting 5 0.5

Along roadside Path, steps away from home 10 1 .0Commercial areas* 10 0.9 Backgrounds, fences, walls, trees, shrubbery 20 2 .0Intermediate areas* 5 0 .5 Flower beds, rock gardens 50 5 .0Residential areas* 2 0 .2 Trees, shrubs (when emphasized) 50 5 .0

Distant from roadside 5 0 .5 Focal points (large) 100 10 .0

Bulletin and posterboards, signs Focal points (small) 200 20 .0

Bright surroundings Loading and unloadin g platforms 200 20 . 0Light surfaces 5 0 5

Parking areasDark surfaces 1000 1000

Self parking 10 1 .0Dark surroundings

Attendant parking 20 2 .0Light surfaces 200 20 .0Dark surfaces 500 50 .0 Piers

Freight 200 2 .0Roadways

Passenger 200 2 .0Expressways

Active shipping area surrounding 50 5 .0Commercial areas* 14 1 .4

Intermediate areas* 12 1 2 Playground 50 5 .0

Residential areas* 9 9 Badminton (outdoor)Major Roads Recreational 100 10

Commercial areas* 17 1 .7 Club 200 20Intermediate areas* 13 1 .3

BaseballResidential areas* 9 9

RecreationalCollector roads

Infield 105 15Commercial areas* 12 1 .2

Outfield 100 10Intermediate areas* 9 0 .9

Junior League (Class I and 11)Residential areas* 6 06

540-13

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Table 540-3. RECOMMENDED LEVELS OF ILLUMINATION (continued)

Area/activity Outdoor facilities Lux Footcandles Area/activity Outdoor facilities Lux Footcandles

(Ix) (fc) (Ix) (fc)

Infield 300 30 Outfield 70 7

Outfield 200 20 Slow pitch, tournament

Infield 200 20Semipro and municipal league

200Outfield 150 15

Infield 20

Outfield 150 15Recreational (6-pole)

Infield 100 10On seats during game 20 2

Outfield 70 7On seats before and after game 50 5

Industrial LeagueBasketball (o utdoor) recreational 100 10 Infield 200 20

FootbalI Outfield 150 15

Distance from nearest sideline to the Semiprofessionalfarthest rows of spectators :

Infield 300 30Class I

(over 30,000 spectators) Outfield 200 20

over 100 ft (30 m) 1000 100Professional and championship

Class II Infield 500 50(10 to 15,000 spectators)15 to 30 m (50 to 100 ft) 500 50 Outfield 300 30

Class III(5 to 10,000 spectators) Swimming (outdoo r)

9 to 15 m (30 to 50 ft) 300 30-

Recreational 100 10

Class IVUnderwater 600 (60)

(under 5,000 spectators)under 9 m (30 ft) 200 20 Exhibitions 200 20

Class V(no fixed seating facilities) 100 10 Tennis (outdoo r)

Recreational 100 10Handball a nd racquetball (outdoo r)

-Club 200 20

Recreational (two-court) 100 10

Tournament 300 30Club (two-court) 200 20

VolleyballHockey (outdoor)

-

Recreational 100 10Recreational 100 10

Tournament 200 20Amateur 200 20

Horse shows Source: Illuminating Engineering Society of North America, Mark Rea, (ed .) .

Recreational 50 5 IES Lighting Handbook, Reference Volume and Application Volume, IES, New

York, 1993 .Tournament 100 10

Shuffleboard *Areas are defined as follows :

Recreational 50 5 Commercial areas : Dense business districts with heavy vehicular and pedestri-

an traffic throughout the day and night .

S kating _ Intermediate areas : Moderately heavy pedestrian traffic during nights

Roller rink 100 10 (libraries, recreation centers, large apartment complex, neighborhood retail

stores) .Ice rink (outdoor) 50 5

Residential areas: Predominantly a residential area with light pedestrian traffic

Lagoon, pond, or flooded area 10 1 at night (single family,multifamily apartments) .

Ski slope 10 1

Soccer (see Football)

Softball

Slow pitch, recreational (6 pole)

Infield 100 10

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5 .0 LOW VOLTAGE SYSTEMS

Low voltage lighting systems offer an alter-native to more energy-consumptive 120volt systems . These systems work particu-larly well in informal, small-scale, residentialsettings . In addition to reduced energyusage, low voltage systems offer safe andeasy installation, longer lamp life (up totwice as long as 120 volt lamps), small fix-tures that can be hidden in the landscape,and very low light levels to achieve a vari-ety of lighting effects . Low voltage systemsare not typically appropriate for larger pro-jects requiring significant levels of illumina-tion, or public sites where durability is aconcern .

Low voltage systems include a trans-former, cable, connectors, and the fixtures.Figure 540-26 illustrates the componentsof a typical system .

Transformers are required to convertstandard 120 volt output to the properoperating voltage . They must provide ade-quate power to accommodate all fixturesproposed, including anticipated expansion .The transformer's wattage rating must beequal to or greater than the wattage of allfixtures combined . Large or diverse lightingschemes may require multiple transformers.Transformers may use manual, automatictimer, or photocell systems that detect lightlevels to turn power on and off for the sys-tem . Current photocell technology is suit-

able only for small-scale residential applica-tions due to reliability concerns .

Systems typically use 12 gauge low volt-age cable feeds with 18 gauge fixture wire,unless otherwise specified by the manufac-turer. Plastic connectors are used to joineach fixture to the cable feed .

A wide variety of low voltage fixtures areavailable to achieve various lighting effects .Refer to 4 .4 Landscape Lighting Effects inthis section for information on differentlighting strategies .

6.0 RECOMMENDED LEVELSOF ILLUMINATION

The levels of illumination listed in Table540-3 represent current standards in thelighting industry.

REFERENCES

Iluminating Engineering Society of NorthAmerica, Recommended Lighting forWalkways and Class 1 Bikeways, DG-5,1993 .

Moyer, Jan Lennox, The LandscapeLighting Book, John Wiley & Sons, NewYork, 1992 .

Rea, Mark (ed.) . Lighting Handbook :Reference & Application, IlluminatingEngineering Society of North America,1993 .