Roadway lightingRoadway lighting

Roadway lighting is one of the most Roadway lighting is one of the most common exterior lighting applications. common exterior lighting applications.

provides illumination for drivers, provides illumination for drivers, pedestrians and associated users. pedestrians and associated users.

is a key element in the development of is a key element in the development of many urban and rural areas. many urban and rural areas.

requires large investment in energy requires large investment in energy useuse

Roadway lightingRoadway lightingMethods for specifying efficient products and Methods for specifying efficient products and

maintaining aesthetically pleasing maintaining aesthetically pleasing installations provide : installations provide :

energy efficiency benefits, energy efficiency benefits,

potential economic benefits potential economic benefits

(by increased commercial activity and (by increased commercial activity and tourism)tourism). .

The The science science and and art art of roadway lighting :of roadway lighting :

new and more efficient light sources, new and more efficient light sources,

improved luminaires and controls, improved luminaires and controls,

new standards of roadway lighting new standards of roadway lighting practices practices

PURPOSE OF ROADWAY LIGHTINGPURPOSE OF ROADWAY LIGHTING

Promotion of safety by providing quick, Promotion of safety by providing quick, accurate, and comfortable vision for accurate, and comfortable vision for drivers or motorists and pedestrians.drivers or motorists and pedestrians.

Improvement of traffic flow by providing Improvement of traffic flow by providing light, beyond that provided by vehicle light, beyond that provided by vehicle lights. This aids drivers in orienting lights. This aids drivers in orienting themselves, and delineating roadway themselves, and delineating roadway lighting geometries and obstructions, lighting geometries and obstructions, which reduce vehicular accidents.which reduce vehicular accidents.

Provision of adequate illumination visibility Provision of adequate illumination visibility for safe vehicle operation in long for safe vehicle operation in long underpasses and tunnels. underpasses and tunnels.

Help prevent street crimes.Help prevent street crimes. Increase commerce within the premises.Increase commerce within the premises.

ROADWAY LIGHTING EQUIPMENTROADWAY LIGHTING EQUIPMENT

Roadway lighting equipment can be grouped Roadway lighting equipment can be grouped into three general components :into three general components :

Optical SystemOptical System : light source, reflector, : light source, reflector, refractor and housing. refractor and housing.

Electrical System Electrical System : ballast, wiring, : ballast, wiring, photoelectric control and other minor photoelectric control and other minor components.components.

Structural SystemStructural System : the mounting : the mounting

brackets, pole and foundation supporting brackets, pole and foundation supporting the luminaire and associated equipment.the luminaire and associated equipment.

Light Sources Light Sources for Roadwayfor Roadway LightingLighting

Light sources determine the visual quality, Light sources determine the visual quality, economy, efficiency, and energy conservation economy, efficiency, and energy conservation aspects of the illumination system.aspects of the illumination system.

The factors affect the cost and effectiveness of The factors affect the cost and effectiveness of installing, operating, and maintaining the light: installing, operating, and maintaining the light:

+ the efficiency of a lamp in converting + the efficiency of a lamp in converting electrical electrical energy to light, energy to light,

+ the ability of the lamp to maintain its + the ability of the lamp to maintain its light output light output over the course of the over the course of the lamp life, lamp life,

+ the length of the lamp life, + the length of the lamp life, + the color of the light, + the color of the light, + the distribution of the light.+ the distribution of the light.

CHARACTERISTICS CHARACTERISTICS OF COMMON LIGHT SOURCESOF COMMON LIGHT SOURCES

Color CharacteristicsColor Characteristics

Color RenderingColor Rendering

Color Rendering Index (CRI).Color Rendering Index (CRI).

Correlated Color Temperature Correlated Color Temperature (CCT).(CCT).

Lamp Lumen Depreciation (LLD). Lamp Lumen Depreciation (LLD). Average Rated LifeAverage Rated Life

Color Rendering Index (CRI)Color Rendering Index (CRI)

Color Rendering IndexColor Rendering IndexThe measure of the degree of color shift, which The measure of the degree of color shift, which objects undergo when illuminated by the light objects undergo when illuminated by the light source, as compared with the color of those source, as compared with the color of those same objects when illuminated by a reference same objects when illuminated by a reference source of comparable color temperature.source of comparable color temperature.

The CRI uses filament light as a base for 100 and The CRI uses filament light as a base for 100 and the warm white fluorescent for 50. Values for the warm white fluorescent for 50. Values for common light sources vary from about 20 to 99. common light sources vary from about 20 to 99.

The higher the number, the better the color The higher the number, the better the color rendering or color appearance (less color shift or rendering or color appearance (less color shift or distortion occurs).distortion occurs).

Correlated Color Temperature (CCT)Correlated Color Temperature (CCT)

Correlated Color TemperatureCorrelated Color TemperatureThe absolute temperature (in Kelvin) of a blackbody The absolute temperature (in Kelvin) of a blackbody

radiator whose chromaticity nearly resembles that radiator whose chromaticity nearly resembles that of the light source. of the light source.

The chromaticity of general lighting lamps, measured The chromaticity of general lighting lamps, measured in Kelvin (K) falls in the range 2200 to 7500K. in Kelvin (K) falls in the range 2200 to 7500K.

The CCT indicates visual “warmth” or “coolness”. The CCT indicates visual “warmth” or “coolness”. At 4000K and above, the chromaticity usually At 4000K and above, the chromaticity usually described as “cool”. described as “cool”. Around 3500K, sources have a neutral appearance. Around 3500K, sources have a neutral appearance. At 3000K and below, the lighting effect is judged to At 3000K and below, the lighting effect is judged to be “warm”.be “warm”.

CHARACTERISTICSCHARACTERISTICS OF COMMON LIGHT SOURCES OF COMMON LIGHT SOURCES (cont.)(cont.)

Lamp Lumen Depreciation (LLD) Lamp Lumen Depreciation (LLD) The fractional loss of lamp light output in The fractional loss of lamp light output in lumens at rated operating conditions that lumens at rated operating conditions that progressively occurs during lamp operation. progressively occurs during lamp operation. Lamps produces less light as it ages and near Lamps produces less light as it ages and near end of life. LLD is caused by lamp coating and end of life. LLD is caused by lamp coating and electrode filament deterioration.electrode filament deterioration.

Average Rated LifeAverage Rated Life. . The life value assigned to a particular type The life value assigned to a particular type lamp. It is commonly statistically determined lamp. It is commonly statistically determined estimate of average or of median operational estimate of average or of median operational life. Rated life is the point at which 50% of a life. Rated life is the point at which 50% of a large group of lamps is expected to fail under large group of lamps is expected to fail under standard or specified test conditions.standard or specified test conditions.

LIGHT SOURCES LIGHT SOURCES FOR ROADWAY LIGHTINGFOR ROADWAY LIGHTING

Most roadway lighting installations use Most roadway lighting installations use one of three types of high intensity one of three types of high intensity discharge (HID) lamps :discharge (HID) lamps :

Mercury Vapor (MV) lamps, Mercury Vapor (MV) lamps, Metal Halide (MH) lamps,Metal Halide (MH) lamps,High Pressure Sodium (HPS) lamps,High Pressure Sodium (HPS) lamps,

(the most commonly (the most commonly used).used).

Lamp IdentificationLamp Identification

In present practice,In present practice,the designation commonly starts the designation commonly starts with the following letter:with the following letter:

"H" for mercury vapor"H" for mercury vapor"M" for metal halide"M" for metal halide"S" for high pressure sodium"S" for high pressure sodium

This is followed usually by designations that identify This is followed usually by designations that identify the electrical characteristics of the lamp and the electrical characteristics of the lamp and

ballast; ballast; the size and shape of the lamp; the size and shape of the lamp; the wattage and color of the lamp.the wattage and color of the lamp.

Color temperature, base type and mounting (burning) Color temperature, base type and mounting (burning) position designations may also be added.position designations may also be added.

Mercury Vapor LampsMercury Vapor LampsMercury Vapor Lamp is an HID lamp in which the Mercury Vapor Lamp is an HID lamp in which the major portion of the light is produced by radiation major portion of the light is produced by radiation from mercury operating at a partial pressure in from mercury operating at a partial pressure in excess of 105Pa (# 1atm).excess of 105Pa (# 1atm).

Mercury Vapor LampsMercury Vapor LampsConstruction and Operation. Construction and Operation. The outer glass envelope of the mercury lamp The outer glass envelope of the mercury lamp

is made of a borosilicate hard glass, which is is made of a borosilicate hard glass, which is needed to withstand the high operating needed to withstand the high operating temperature of the lamp. temperature of the lamp.

This outer glass shell absorbs much of the UV This outer glass shell absorbs much of the UV radiation emitted by the mercury arc. radiation emitted by the mercury arc.

Some mercury vapor lamps have a self Some mercury vapor lamps have a self extinguishing feature to shut the lamp off if the extinguishing feature to shut the lamp off if the outer glass bulb is broken, preventing outer glass bulb is broken, preventing exposure to ultraviolet radiation.exposure to ultraviolet radiation.

Mercury Vapor LampsMercury Vapor Lamps

Metal Halide LampsMetal Halide LampsMetal Halide Lamp is an HID lamp in which the Metal Halide Lamp is an HID lamp in which the major portion of the light is produced by major portion of the light is produced by radiation of metal halides and their products of radiation of metal halides and their products of dissociation possibly in combination with dissociation possibly in combination with metallic vapors such as mercury.metallic vapors such as mercury.

Metal Halide LampsMetal Halide LampsSimilar in construction to mercury lamps, metal Similar in construction to mercury lamps, metal

halide lamps provide white light at higher halide lamps provide white light at higher efficacies and with better lumen maintenance than efficacies and with better lumen maintenance than mercury sources (due to metal halides in the arc mercury sources (due to metal halides in the arc tube). tube).

Metal halides may feature a phosphor coating that Metal halides may feature a phosphor coating that converts the excess UV into visible light, improving converts the excess UV into visible light, improving the lamp's CRI rating in the process.the lamp's CRI rating in the process.

Metal Halide LampsMetal Halide Lamps

High pressure Sodium LampsHigh pressure Sodium Lamps

In HPS Lamps, light is produced by radiation from In HPS Lamps, light is produced by radiation from sodium vapor operating at a partial pressure There sodium vapor operating at a partial pressure There exist clear and diffuse coated lamps.exist clear and diffuse coated lamps.

High pressure Sodium LampsHigh pressure Sodium LampsThe outer glass envelope of a high pressure sodium The outer glass envelope of a high pressure sodium

lamp is made of a borosilicate hard glass, which lamp is made of a borosilicate hard glass, which is needed to withstand the high operating is needed to withstand the high operating temperature of the lamp. temperature of the lamp.

The arc discharge is produced by a mixture of The arc discharge is produced by a mixture of xenon and a sodium mercury amalgam in the xenon and a sodium mercury amalgam in the polycrystalline alumina arc tube.polycrystalline alumina arc tube.

High pressure Sodium LampsHigh pressure Sodium Lamps

HPS with StarterHPS with Starter

Characteristics of Lamps for Characteristics of Lamps for Roadway LightingRoadway Lighting

TypeType RatingRating

ww

InitialInitialOutputOutput

lmlm

EfficacyEfficacy

lm/Wlm/W

CRICRI ColorColorTemp.Temp.

ooKK

ColorColorAppearanceAppearance

Warm-upWarm-upTimeTime

minmin

RestrikeRestrikeTimeTime

minmin

Ave.Ave.Op. Op.

HoursHours

MVMV 4040toto

10001000

12,00012,000toto

13,00013,000

30­6530­65 15­2015­20 56005600toto

70007000

CoolCool““blue­green”blue­green”

3­53­5 55 10,00010,000toto

16,00016,000

MHMH 3232toto

1,5001,500

19,50019,500toto

26,30026,300

70­12570­125 60­9660­96 30003000toto

60006000

white­lightwhite­light 2­102­10 1515 3,0003,000toto

20,00020,000

HPSHPS 3535toto

10001000

23,00023,000toto

28,50028,500

60­14060­140 22­6522­65 21002100toto

22002200

yellow­orangeyellow­orange 3­53­5 3­43­4 10,00010,000toto

24,00024,000

SELECTION OF LIGHTING EQUIPMENT SELECTION OF LIGHTING EQUIPMENT FOR ROADWAY LIGHTINGFOR ROADWAY LIGHTING

AFFECTING FACTORSAFFECTING FACTORS

lamp lumen output.lamp lumen output. lamp life.lamp life. lamp lumen depreciation.lamp lumen depreciation. luminaire lamp distribution.luminaire lamp distribution. lamp restrike time.lamp restrike time. lamp color.lamp color. surrounding or ambient temperature.surrounding or ambient temperature. physical size of lamp and luminaire.physical size of lamp and luminaire. physical durability of lamp and luminaire.physical durability of lamp and luminaire. cost.cost.

LAMP INSTALLATION POSITIONLAMP INSTALLATION POSITION The output of some type of lamps is sensitive to The output of some type of lamps is sensitive to

lamp position. Choose the right lamp for the lamp position. Choose the right lamp for the intended position for installation.intended position for installation.

Manufacturers classify their products into 3 Manufacturers classify their products into 3 categories: categories:

Vertical base up (VBU) Vertical base down (VBD) Vertical base up (VBU) Vertical base down (VBD)

Horizontal positionHorizontal position

Type of LightType of LightSourcesSources

AdvantagesAdvantages DisadvantagesDisadvantages

Mercury­vapor­lamps­Mercury­vapor­lamps­ ·­­Long­life­·­­Long­life­·­­Good­luminaire­light­control­·­­Good­luminaire­light­control­·­­Small­luminaire­size­·­­Small­luminaire­size­

·­­Long­restrike­time­·­­Long­restrike­time­·­­High­lumen­depreciation­·­­High­lumen­depreciation­·­­Poor­lamp­efficacy·­­Poor­lamp­efficacy

Metal­halide­lamps­Metal­halide­lamps­ ·­­High­CRI­·­­High­CRI­·­­High­lamp­efficacy­·­­High­lamp­efficacy­·­­Good­luminaire­light­control­·­­Good­luminaire­light­control­·­­Small­luminaire­size­·­­Small­luminaire­size­

·­­Long­restrike­time­·­­Long­restrike­time­·­­High­lumen­depreciation­·­­High­lumen­depreciation­·­­Poor­lamp­efficacy­·­­Poor­lamp­efficacy­­­­­­­­­­­­­­­­­­­(photopic­efficiency)(photopic­efficiency)

High­pressure­sodium­High­pressure­sodium­lamps­lamps­

·­­Long­lamp­life­·­­Long­lamp­life­·­­High­lamp­efficacy­·­­High­lamp­efficacy­·­­Good­luminaire­light­control­·­­Good­luminaire­light­control­·­­Small­luminaire­size­·­­Small­luminaire­size­·­­Minimal­lumen­depreciation­·­­Minimal­lumen­depreciation­

·­­Low­CRI­·­­Low­CRI­·­­Restrike­time­required·­­Restrike­time­required

LIGHT LOSS FACTORLIGHT LOSS FACTOR

LIGHT LOSS FACTOR (Maintenance Factor)LIGHT LOSS FACTOR (Maintenance Factor) The light loss factor (LLF) is the ratio of the illuminance The light loss factor (LLF) is the ratio of the illuminance

when it reaches its lower level just before corrective when it reaches its lower level just before corrective action is taken as compared to the initial level. action is taken as compared to the initial level.

This is estimated by a study of This is estimated by a study of

the conditions under which the system will the conditions under which the system will operate, operate,

the atmospheric conditions, the atmospheric conditions,

the frequency of cleaning, and the frequency of cleaning, and

the depreciation of the lighting effect.the depreciation of the lighting effect. The LLF are divided into two categoriesThe LLF are divided into two categories

unrecoverable unrecoverable

recoverable.recoverable.

LIGHT LOSS FACTORLIGHT LOSS FACTOR

Unrecoverable Light Loss FactorUnrecoverable Light Loss Factor. . attributed to equipment and site conditions that attributed to equipment and site conditions that cannot be changed with normal maintenance cannot be changed with normal maintenance procedure. procedure.

(temperature factor, line voltage factor, (temperature factor, line voltage factor, ballast factor, luminaire surface depreciation, ballast factor, luminaire surface depreciation, equipment operating factor, and the lamp equipment operating factor, and the lamp positioning factors).positioning factors).

Recoverable Light Loss FactorRecoverable Light Loss Factor. . can be changed by regular scheduled maintenance.can be changed by regular scheduled maintenance.

(cleaning and relamping luminaires, cleaning (cleaning and relamping luminaires, cleaning and painting room surfaces, lamp lumen and painting room surfaces, lamp lumen depreciation, luminaire dirt depreciation, and lamp depreciation, luminaire dirt depreciation, and lamp burnouts).burnouts).

LIGHT LOSS FACTORLIGHT LOSS FACTOR

Calculations for Total Light Loss FactorCalculations for Total Light Loss Factor. .

The total light loss factor is simply the The total light loss factor is simply the product of all the individual factors that product of all the individual factors that contribute to the loss of light. contribute to the loss of light.

Where factors are not known, or applicable, Where factors are not known, or applicable, they are assumed to be unity (or may be they are assumed to be unity (or may be omitted in the calculation).omitted in the calculation).