How to Design Efficient Street Lighting-Part-4

(F) Lighting Pollutions

  • Light pollution is an unwanted consequence of outdoor lighting and includes such effects as sky glow, light trespass, and glare. 
  • 30 to 50% of all light pollution is produced by roadway lighting that shines wasted light up and off target.

(1) Glare:

  • Glare is the condition of vision in which there is discomfort or a reduction in the ability to see significant objects. Glare affects human vision and it is subdivided into four components, Disability Glare, Discomfort Glare, Direct Glare and Indirect Glare.
  • By origin
  1. Direct Glare
  2. Indirect (reflected) Glare
  • By effect on people
  1. Disability Glare
  2. Discomfort Glare
  • Disability glare:
  • Disability glare is the glare that results in reduced visual performance and visibility.
  • Since disability glare reduces the ability to perceive small contrasts.
  • It can impair important visual tasks in traffic such as detecting critical objects, controlling headlights, and evaluating critical encounters, making glare a potential danger for road users.
  • LED light sources can provide very high luminance lev­els which may cause glare. For this reason, LED lamps are commonly equipped with diffusers to reduce this luminance.
  • Disability glare may vary for dif­ferent individuals and it can be calculated objectively.
  • In a particu­lar illuminated environment, the human eye will be able to detect differences in luminance down to a certain threshold. This threshold can be compared for a situa­tion in the same environment when a source of glare is added. By comparing these thresholds, the threshold increment can be derived.
  • Discomfort glare:
  • Discomfort glare is the glare producing discomfort. It does not necessarily interfere with visual performance or visibility.
  • As vertical light angles increase, discomforting glare also increases
  • Discomfort glare, on the other hand, is a subjective phenomenon and there is no method for its Rating.
  • Although the 9-point De Boer scale (ranging from “1” for “unbearable” to “9” for “unno­ticeable”) is the most widely used in the field of auto­motive and public lighting.
  • Direct Glare:
  • Direct glare is caused by excessive light entering the eye from a bright light source. The potential for direct glare exists anytime one can see a light source. With direct glare, the eye has a harder time seeing contrast and details.
  • A system designed solely on lighting levels, tends to aim more light at higher viewing angles, thus producing more potential for glare.
  • Exposed bright light source, for example a dropped lens cobra head or floodlight causes of direct glare.
  • Direct glare can be minimized with careful equipment selection as well as placement.

  • Figure illustrates two examples of exterior lighting that results in glare. 

  •  Fig shows how full cutoff luminaries (Shielded Luminaires) can minimize this direct glare. In exterior applications, use fully shielded luminaires that directs light downwards towards the ground.
  • Indirect Glare:
  • Indirect glare is caused by light that is reflected to the eye from surfaces that are in the field of view – often in the task area.
  • Indirect Glare can be minimized with the type and layout of lighting equipment. Direct the light away from the observer with the use of low glare, fully shielded luminaries.
  • As the uniformity ratio increases (poor uniformity), object details become harder to see.
  • For roadway lighting, good uniformity shows evenly lighted pavement. However, to meet small target visibility criteria, a non uniform roadway surface may be better.
  • There should be a balance between uniform perception and detecting objects on the road. Also, emphasis is put on horizontal surface uniformity. In reality, vertical surfaces may require more lighting in order to improve guidance.
  • How to Reduce Glare:
  • Glare and light trespass are more concern when installing floodlights.
  • Use shielded Light should be use to reduce Glare.
  • Higher mounting heights can more effective in controlling spill light, because floodlights with a more controlled light distribution (i.e., narrower beam) may be used, and the floodlights may be aimed in a more downward direction, making it easier to confine the light to the design area.
  • Lower mounting heights increase the spill light beyond the property boundaries. To illuminate the space satisfactorily, it is often necessary to use floodlights with a broader beam and to aim the floodlights in directions closer to the horizontal than would occur when using higher mounting heights.
  • Lower mounting heights make bright parts of the floodlights more visible from positions outside the property boundary, which can increase glare.

(2) Sky glow:

  • Sky Glow is brightening of the night sky caused by outdoor lighting.
  • Light that is emitted directly upward by luminaries or reflected from the ground is scattered by dust and gas molecules in the atmosphere, producing a luminous background. It has the effect of reducing one’s ability to view the stars in Night. 

  • How to Reduce Sky Glow
  • While it is difficult to accurately model sky glow, at this point it is presumed that the most important factors are light output and lamp spectral characteristics, light distribution from the luminaire, reflected light from the ground, and aerosol particle distribution in the atmosphere.
  • If the quantity of light going into the sky is reduced, then sky glow is reduced. Thus, to reduce sky glow by
  • By using full cutoff luminaires to minimize the amount of light emitted upward directly from the luminaire.
  • Reduce Lighting Level.
  • Make practice to Turn off unneeded lights
  • Limited Lighting hours in outdoor sales areas, parking areas, and signages
  • Installing Low-Pressure Sodium light sources, which allow astronomers to filter the line spectra from telescopic images.

 (3) Light Trespass:

  • Light trespass is condition when spill (Unwanted or Unneeded) light from a streetlight or floodlight enters a window and illuminates an indoor area.
  • How to Reduce Trespass
  • Select luminaries, locations, and orientations to minimize spill light onto adjacent properties.
  • Use well-shielded luminaries.
  • Keep floodlight aiming angles low so that the entire beam falls within the intended lighted area.

Difference between full cutoffs and fully shielded:

  • The full cutoff has is luminaries that have no direct up light (no light emitted above horizontal) and 10% of light intensity between 80° and 90°.
  • The term full cutoff is often substituted for the term fully shielded.
  • The both terms are not equivalent. Fully shielded luminaires emit no direct up light, but have no limitation on the intensity in the region between 80° and 90°
  • Luminaires that are full cutoff, cutoff, semi cutoff, and non cutoff , may also qualify as fully shielded.

  • There is also a confusing assumption that a luminaire with a flat lens qualifies as a full cutoff luminaries. While this may be true or not in some Lighting Fixtures case.

  • Fully shielded means, a lighting fixture constructed in such a manner that the bulb should be fully recessed into Fixture so that all light is directed downward below the horizontal.
  • The fixture is angled so the lamp is not visible below the barrier (no light visible below the horizontal angle).

(G) Selection of Luminas:

(1) Types of Lighting Source

  • Street Lights are mostly Low-pressure sodium (LPS), High-pressure sodium (HPS), Metal halide and Light emitting diodes (LED).
  • LPS is very energy efficient but emits only a narrow spectrum of pumpkin-colored light that some find to be undesirable.
  • LPS is an excellent choice for lighting near astronomical observatories and in some environmentally sensitive areas.
  • HPS is commonly used for street lighting in many cities. Although it still emits an orange-colored light, its coloring is more “true to life” than that of LPS.
  • Where it’s necessary to use white light, there are metal halide and LEDs.

  • High-pressure sodium lamps should be used for expressways, main roads, secondary roads and branch roads.
  • Low-power metal halide lamps should be used in mixed traffic roads for motor vehicles and pedestrians in residential areas.
  • Metal halide lamps can be used for motor vehicle traffic, such as city centers and commercial centers, which require high color identification.
  • Metal halide lamps, CFL lamps are used at Pedestrian streets in industrial areas, sidewalks in residential areas, and sidewalks on both sides of motorway traffic.
  • LED streetlights are more durable, longer lasting, efficiency, dimmable capacity and cost effective than traditional lights.
  • LED also enhances public safety by delivering superior visible light while providing the environmental advantage of using less energy.

(2) Color Rendering Index (CRI):

  • CRI Measures the ability of the artificial light to show or reproduce the colors of the road or objects on the road, relative to a natural light source.
  • The natural light source (the sun) has CRI of 100. The higher
  • This index the better the visibility will be. For all types of road CRI ≥ 70 is recommended.
  • Efficacy
  • At the low end LED efficacy starts at 70 lumens per watt (lm/W) and reaches as high as 150 lm/W.
  • While the mean efficacy for outdoor area fixtures is slightly lower than common indoor fixtures such as troffers and linear lighting about 100 lm/W for area lights compared to about 110 lm/W for troffers and linear fixtures this difference is not significant. It may be the result of outdoor area lights requiring more precise luminous intensity distributions and other factors unique to outdoor lighting.

(3) Fixture Protection:

  • When using sealed road lighting, the protection level of the light source cavity should not be lower than IP54.
  • For roads and places with dangerous environmental pollution and heavy maintenance, the protection level of the light source cavity should not be lower than IP65.
  • The degree of protection of the lamp electrical appliance cavity should not be lesser than IP43.
  • Lamps with excellent corrosion resistance should be used in areas or places with high levels of corrosive gases such as acid and alkali in the air.

(H) Effective Road Lighting:

  • Sufficient illumination.
  • Good uniformity.
  • No Glare.
  • Low consumption.
  • No Color Temperature abnormalities
  • No Zebra effect
  • Shielded lighting to ensure light is pointed downwards
  • Completely uniform illuminance.
  • No requirement for over lighting to obtain sufficient average illumination.
  • Absence of glare.
  • Absence of low angle radiation that causes sky glow.
  • Control of light trespass.
  • High redundancy.

Effective Road Lighting 



Proper pole height & spacing

 Provide uniform light distribution

Proper Luminaire aesthetics

 Blends in with the surroundings
Good maintenance

Reduce problems in lightning

High lamp efficiency

 Minimize energy cost

Life of Luminaire

Reduce lamp replacement cost
Good color rendering

 Helps object appear more natural

Proper light distribution

 Provide required light on roads

Cost effectiveness

 Lowers operating cost

Minimizing light pollution & glare

 Reduce energy use

Effective Energy-efficient Street Lighting Systems (NYSERDA, 2002)



Proper pole height and spacing Provides uniform light distribution, which improves appearance for safety and security Meets recommended light levels Minimizes the number of poles, reducing energy and maintenance costs
Proper luminaire aesthetics Blends in with the surroundings
High lamp efficacy and Luminaire efficiency Minimizes Energy cost
Life of the luminaire and other components Reduces lamp replacement costs
Cost effectiveness Lowers operating cost
High Lumen Maintenance Reduces lamp replacement costs
Good color rendering Helps object appear more natural and pleasing to the public Allows better recognition of the environment, improves security
Short lamp Re strike Allows the lamp to quickly come back after a power interruption
Proper light distribution Provides required light on the roads and walkways
Proper Cutoff Provides adequate optical control to minimize light pollution
Minimizing light pollution and Glare Reduces energy use
Automatic Shutoff Saves energy and maintenance costs by turning lamps off when not needed

Minimum Value of Street Light Designing


Min Value


Lumens Per Watt

80 To 140



50 To 60Hz

Power Factor

  More than 95


 < 20%
Life Hours

70,000 hours

Color Temperature

4000K  To  5000K


More than 75

Beam Angle / Beam Pattern

 Type 2,3,4,5
Operating Temperature

(-)25°C To (+)50°C

Working Humidity

10% To 90% RH
IP Rating




Optic Lens Material

High Polycarbonate (PMMA)
Forward Current



IP65 – Aluminum Alloy and PC Lens


 18.23″ X 13.58″ X 4.57″


 15.30 lbs – 34.39 lbs

10 Years



How to Design Efficient Street Lighting-Part-3

(C) Lighting Factor:

(1) Maintenance Factor (Light Loss Factors) (MF)

  • The Maintenance Factor (Light loss factor) is the combination of factors used to denote the reduction of the illumination for a given area after a period of time compared to the initial illumination on the same area.
  • The efficiency of the luminaire is reduced over time. The designer must estimate this reduction to properly estimate the light available at the end of the lamp maintenance life.
  • Luminaire maintenance factors vary according to the intervals between cleaning, the amount of atmospheric pollution and the IP rating of the luminaire.
  • However, it is proposed to consider maintenance factor of not less than 0.5 for LED Road lighting installations for IP66 rated luminaires.
  • The maintenance factor may range from 0.50 to 0.90, with the typical range between 0.65 To 0.75
  • These maintenance factor values shall be adopted for the purposes of producing the lighting simulation design.
  • The maintenance factor is the product of the following factors.
  • LLF = LLD x LDD x EF
  • Mostly We consider Maintenance factor from 0.8 to 0.9
  • We have to choose Maintenance factor carefully by increasing maintenance factor 0.5 the spacing of pole increasing 2 meter to 2.5 meter
Maintenance Factor Max. Spacing of Pole (Meter)
0.95 43
0.9 40.5
0.85 38
0.8 36

(a) Lamp Lumen Depreciation Factor (LLD)

  • As the lamp progresses through its service life, the lumen output of the lamp decreases. This is an inherent characteristic of all lamps. The initial lamp lumen value is adjusted by a lumen depreciation factor to compensate for the anticipated lumen reduction.
  • This assures that a minimum level of illumination will be available at the end of the assumed lamp life, even though lamp lumen depreciation has occurred. This information should be provided by the manufacturer. For design purposes, a LLD factor of 0.9 to 0.78 should be used.

(b)Luminaire Dirt Depreciation Factor (LDD).

  • Dirt on the exterior and interior of the luminaries and to some on the lamp reduces the amount of light reaching the roadway.
  • Various degrees of dirt accumulation may be anticipated depending upon the area in which the luminaire is located. Industry, exhaust of vehicles, especially large diesel trucks, dust, etc, all combine to produce the dirt accumulation on the luminaries.
  • Higher mounting heights, however, reduce the vehicle-related dirt accumulations.

LDD factor of 0.87 to 0.95 should be used. This is based on a moderately dirty environment and three years exposure time.

(c) Equipment Factor (EF).

  • Allows for variations inherent in the manufacture and operation of the equipment (i.e., luminaries, system voltage and voltage drop).
  • It is generally assumed to be 95%.

(2) Coefficient of Utilization (CU):

  • Coefficient of Utilization is the ratio of the luminous flux from a luminaire received on the surface of the roadway to the lumens emitted by the luminaire’s lamps alone.
  • Coefficient of Utilization should be maximum.
  • Coefficient of Utilization differs with each luminaire type, and depends upon mounting height, road width, and overhang.
  • The coefficient of utilization (K) should be over 30% or the utilance above 40% for the road, highway, square or enclosure. Luminaires or floodlights should not by placed far from the area to be lit or, where appropriate, light projection beyond the useful zone should be minimized (K = average maintained illuminance multiplied by the surface calculation and divided by the lumens installed).

Various Factors

Type Luminaries Dirt Depreciation Luminaire Lumen Depreciation Total Light Loss Factor
LED 0.9 0.85 0.765
HPS 0.9 0.9 0.81
LPS 0.9 0.85 (0.7 for 180W) 0.765 (0.63 for 180W)

Light Loss Factors

Type of Lamp Laminar Dirt description Light Loss Factor
HPS 0.88 0.74
Induction 0.88 0.62
LED 0.88 0.72

Maintenance factors

Cleaning intervals (months) Pollution category
High Medium Low
12 0.53 0.62 0.82
18 0.48 0.58 0.8
24 0.45 0.56 0.79
36 0.42 0.53 0.78
Maintenance Factors for 36 month cleaning interval
Factors IP5X IP6X
Pollution category Pollution category
Low Medium High Low Medium High
LMF 0.88 0.82 0.76 0.9 0.87 0.83
LLMF 0.89 0.89 0.89 0.89 0.89 0.89
MF 0.78 0.73 0.68 0.80 0.77 0.74


(E) Lighting Uniformities

(1) Lighting Uniformities

  • Uniformity is a description of the smoothness of the lighting pattern or the degree of the intensity of bright and dark areas on the road.
  • Uniformity is a measure of how evenly distributed the light on the road is, which can be expressed as Overall Uniformity (UO) and Longitudinal Uniformity (UL).
  • The uniformity ratio shall not exceed 4:1 and preferably should not exceed 3:1 except on residential streets, where 6:1 may be acceptable.

(a) Overall uniformity:

  • In design, the overall uniformity (UO) is expressed as a ratio of the minimum to the average luminance on the road surface of the carriageway within the calculation area.
  • UO=Lmin / Lave

  • It is a measure of how evenly or uniformly illuminate on the road surface.
  • A good overall uniformity ensures that all spots and objects on the road are sufficiently lit and visible to the motorist.
  • The industry accepted value for UO is 30 to 0.40.

(b) Longitudinal uniformity:

  • The longitudinal uniformity (UL) is expressed as the ratio of the minimum to maximum luminance along the center line of a lane within the calculation area.
  • UL=Lmin / Lmax.
  • Longitudinal uniformity is a measure to reduce bright and dark bands of light appearing on road lit surfaces. The effect can be somewhat hypnotic and present confusing luminance patterns.

  • It is a measure to reduce the intensity of bright and dark banding on road lit surface.
  • A good level of longitudinal uniformity ensures comfortable driving conditions by reducing the Pattern of high and low luminance levels on a road (i.e. zebra effect).
  • It is applicable to long continuous roads.

 Combination of Overall Uniformity and Longitudinal Uniformity:

  • The picture on the left shows a road with good UO while the picture on the right has low level of UO. The Road is more visible in the road with higher UO. Having higher UO allows the motorist to see the road clearly and anticipate potential road hazards (e.g. open manholes, road excavations, sharp objects on the road, people crossing the street).
  • The picture on the right shows a road with low level of UL demonstrating the ‘Zebra Effect’ while the picture on the left has high level of UL without ‘Zebra Effect’.
  • The ‘zebra effect’ can cause discomfort to motorists, posing a risk to road safety. Ensuring good level of uniformity can reduce the luminance level needed.

Lighting Levels

Category Eave ( LUX) Emin  LUX) Uniformity ratios
Emax : Emin Eave : Emin
Express & Main street 30 15 3:01 2.5:1
Suburban shopping street 25 10 5:01 3:01
Subsidiary street 15 10 5:01 3:01
Other streets 15 5 10:01 5:01


 Lux Level

Road Classification Area Classification Average  Lux Uniformity Ratio (Aver./Min.)
Arterial (Minor & Major) Commercial 12 3 to 1
Intermediate 9
Residential 6
Collector (Minor & Major) Commercial 8
Intermediate 6 4 to 1
Residential 4
Local Commercial 6
Intermediate 5 6 to 1
Residential 3
Alleys Commercial 4
Intermediate 3 6 to 1
Residential 2
Sidewalks (Roadside) Commercial 3 3 to 1
Intermediate 6 4 to 1
Residential 2 6 to 1
Pedestrian Ways 15 3 to 1


Illumination for Intersections

Functional Classification Average Maintained Illumination at Pavement by Pedestrian Area Classification in Lumen Uniformity
High Medium Low Eavg/Emin
Major/Major 37 28 19 32
Major/Collector 31 24 16 32
Major/Local 28 22 14 32
Collector/Collector 26 19 16 43
Collector/Local 23 17 11 43
Local/Local 19 15 9 65


Illumination for Pedestrian Areas

Maintained Illuminance Values for Walkways
Area Classification Description E avg (Lux) EV min (Lux) E avg/Emin
High Pedestrian Conflict Mixed Vehicle and Pedestrian 22 11 43
Areas Pedestrian Only 11 5 43
Medium Pedestrian Pedestrian Areas 5 2 43
Conflict Areas
Low Pedestrian Rural/Semi-Rural Areas 2 1 108
Conflict Areas Low Density Residential (2 or fewer dwelling units per acre) 3 1 65
Medium Density Residential (2.1 to 6.0 dwelling units per acre) 4 1 43
Pedestrian Portion of Pedestrian/Vehicular Underpasses Day 108 54 43
Night 43 22 32

 (2) Surround Ratio (SR):

  • Road lighting should be illuminate not only the road, but also the adjacent areas so motorists can see objects in the periphery and anticipate potential road obstructions (e.g., a pedestrian about to step onto the road).
  • The SR is the visibility of the road’s periphery relative to that of the main road itself.
  • As per industry standards, SR should be at least 50.
  • Figure show how road lighting should illuminate both the main road and its periphery.

How to Design Efficient Street Lighting-Part-2

(C) Lighting Fixture:

(1) Fixture’s Mounting Height:

  • Higher mounting heights used in conjunction with higher wattage luminaries enhances lighting uniformity and typically reduces the number of light poles needed to produce the same illumination level.
  • In general, higher mounting heights tend to produce a more cost-effective design. For practical and aesthetic reasons, the mounting height should remain constant throughout the system.
  • The manufacturer’s photometric data is required to determine an appropriate mounting height.
  • Typical mounting heights for highway lighting purposes range from 30 ft to 55 ft (9.1 meter to 16.8 meter).
  • Mounting heights for light towers or High mast is typically 80 ft (24 m) or greater.
  • The installation height is too low, the glare of the lamp increases.
  • As the installation high increase, glare decreases, but the lighting utilization rate decreases.

 (2) Fixtures Classification:

  • The Illuminating Engineering Society of North America (IESNA, IES or BIS1981) provides classifications for luminaires according to their glare control and high-angle brightness.

(a) Full Cutoff (F):

  • A luminaire light distribution is designated as full cutoff (F) when Zero intensity at or above horizontal (90° above nadir) and Less than 10% of lamp lumens at or above 80°.
  • Full-cutoff fixtures reduce glare dramatically and eliminate direct up light by sending all their light toward the ground .This efficiency should translate into lower bulb wattages if the existing poles are used. However, some lighting engineers believe that to achieve the same illumination uniformity as their semi-cutoff counterparts, full-cutoff fixtures need to be mounted either on taller poles or closer together
  • Benefits:
  • Limits spill light on to adjacent property, reduces glare. No light is emitted directly from the luminaries into the sky.
  • Reduce Lighting Pollution.
  • Limitations:
  • May reduce pole spacing to maintain uniformity and increase pole and luminaire quantities.
  • Application:
  • Use for roadway, parking, and other vehicular lighting applications. Minimizes glare and light pollution and light trespass.

(b) Cutoff (C):

  • A luminaries light distribution is designated as cutoff (C) when Less than 2.5% Intensity at or above horizontal (90° above nadir) and Less than 10% of lamp lumens at or above 80°.
  • The direction of maximum intensity may vary but should be below 65º.
  • Benefits:
  • Small increase in high-angle light allows increased pole spacing.
  • Cutoff system is the reduction of glare.
  • Limitations:
  • May allow some up light (Sky Light) from luminaries. Typically a small overall impact on sky glow.
  • Application:
  • Interchange lighting and rural intersections due to the ability to reduce glare.
  • Use in applications where pedestrians are present. Provides more vertical illuminance than Full Cutoff luminaires.
  • Lamp rating should be less than 3200 lumens.
  • The cutoff design is where the luminaire light distribution is less than 25,000 lm at an angle of 90° above nadir (vertical axis) and 100,000 lm at a vertical angle of 80° above nadir.

 (c) Semi Cutoff (S) (Medium Beam Angle):

  • A luminaire light distribution is designated as Semi cutoff (S) when Less than 5% Intensity at or above horizontal (90° above nadir) and Less than 20% of lamp lumens at or above 80°.
  • The direction of maximum intensity may vary but should be below 75º.
  • Benefits:
  • High-angle light accents taller vertical surfaces such as buildings. Most light is still directed downward.
  • Limitations:
  • Little control of light at property line.
  • Potential for increased glare when using high wattage luminaries. Typically directs more light into the sky than cutoff.
  • Application:
  • Used for standard road lighting. Adequate glare control is obtained with reasonable spacing.
  • The principal advantage of the semi-cutoff system is a greater flexibility in sitting.
  • Use in pedestrian areas. If using in residential areas, provide with house side shields to minimize light trespass. Lamp rating should be less than 3200 lumens.
  • For the semi-cutoff design, the luminous flux numbers become 50,000 lm for 90° above nadir and 200,000 lm at a vertical angle of 80° above nadir.
  • Semi-cutoff fixtures create broad cones of light that permit wide spacing between poles. But such fixtures create harsh glare and send some light directly into the sky.

(d) Non Cutoff (N) (Higher Beam Angle):

  • A luminaries light distribution is designated as Non Cutoff (N) when Emit light into all directions.
  • No limitations on light distribution at any angle.
  • There is considerable output near the horizontal plane.
  • Benefits:
  • Uniform luminous surfaces such as internally illuminated signs or globes. Wattage should be limited. Suitable for sports lighting, facade, landscape or other applications where luminaires are tilted due to limitations in pole or fixture locations
  • Limitations:
  • Location and aiming are critical. Most likely of all categories to produce offensive brightness and sky glow.
  • Application:
  • Used in areas with a lot of background light. Non-cutoff luminaries shall not be used at lower mounting heights because of glare.
  • Use for decorative applications only. Lamp rating should be less than 3200 lumens.
  • “Full cut off” fixtures must be installed properly, so that the bottom of the fixture is level with the ground.
  • “Fully Shielded” fixtures do not allow any light to be emitted above the lowest light emitting
  • part, but do not restrict light output in the “glare” zone, 90-80 degrees below horizontal.

  (3) Fixtures Distributions (Optical System):

  • The Illuminating Engineering Society classified series of Fixture distribution patterns as Types I, II, III, IV, and V.

(a) Type I (Two-way):

  • The lateral distribution having a preferred lateral width of 15 degrees in the cone of maximum Lumen.
  • Illumination Pattern: Narrow, symmetric luminance pattern.
  • Fixture Location: This type is generally applicable to a luminaire location near the center of a roadway where the mounting height is approximately equal to the roadway width.
  • Type of Road: The luminaire is placed on the side of the street or edge of the area to be lighted. Most 1or 2 Lane Road
  • Application:

(b) Type II (Two Way) :

  • Light distributions have a preferred lateral width of 25 degrees.
  • Illumination Pattern: Slightly wider illuminance pattern than Type I.
  • Fixture Location: They are generally applicable to luminaires located at or near the side of relatively narrow roadways, where the width of the roadway does not exceed 1.75 times the designed mounting height.
  • Type of Road: The luminaire is placed on the side of the street or edge of the area to be lighted. It produces a long, narrow, oval-shaped lighted area which is usually applicable to narrower streets.

(c) Type III (Bat Wing) :

  • Type III light distributions have a preferred lateral width of 40 degrees.
  • Illumination Pattern: It produces an oval-shaped lighted
  • Fixture Location: This distribution is intended for luminaires mounted at or near the side of medium width roadways, where the width of the roadway does not exceed 2.75 times the mounting height.
  • Type of Road: The luminaire is placed on the side of the street or edge of area to medium width streets.

(d) Type IV (Forward throw “Asymmetric”):

  • Type IV light distributions have a preferred lateral width of 60 degrees.
  • Illumination Pattern: Widest luminance pattern.
  • Fixture Location: This distribution is intended for side-of-road mounting and is generally used on wide roadways where the roadway width does not exceed 3.7 times the mounting height.
  • Type of Road: very wide roadway (4 to 6 Lane)
  • Applications: Type IV often use at perimeters where Spill Light is required and there is no place to add Pole.

(e) Type V:

  • Type V light distributions have a circular symmetry of candlepower that is essentially the same at all lateral angles.
  • Illumination Pattern: It produces a circular, wider lighted area and is usually applicable to wide streets.
  • Fixture Location: The luminaries are mounting at or near center of roadways, center islands of parkway, and intersections.
  • Type of Road: very wide roadway (4 to 6 Lane)
  • Applications: Type V often applies to high-mast lighting.



Pole Arrangement Road Width Type of Distribution
One Side or Staggered up to 1.5 x Mounting Height Types II-III-IV
Staggered or Opposite Beyond 1.5 x Mounting Height Types III & IV
Center of the Roadway Mounting up to 2 x Mounting Height Type I


Type of Classification

Commercial Full Cutoff or Semi Cutoff
Intermediate Full Cutoff or Semi Cutoff
Residential Full Cutoff




Lamp Lumens Mounting Height
≤20,000 Lumen  ≤35 Foot
20,000 To 45,000 Lumen 35 To 45 Foot
45,000 To 90,000 Lumen 45 To 60 Foot


Fixture Mounting Height

Type of LED Luminaries Type of Road Lamp mounting height from the floor level (Meters) Minimum Illumination Level (Lux) at centre of road Color of Illumination
250-260W Above 18 (20 To 22) 5000K-6500K
190W A1 Between 11 To 15 (20 To 22) 5000K-6500K
140-170W A1 Between 9 To 15 (18 To 20) 5000K-6500K
90-120W A2/B1 07 To 11 (15 To 18) 4300K-5600K
70-120W A2/B1 07- To 11 (15 To 18) 4300K-5600K
70-120W B1/B2 06 To 09 (15 To 18) 4300K-5600K
70-50W B1/B2/C1 7 To 9 (12 To 15) 4300K-5600K
45-50W B1/B2/C1 5 To 7 (12 To 15) 4300K-5600K
25-30W B1/B2/C1 5 To 7 (10 To 12) 4300K-5600K


Relationship between mounting height and spacing

Mounting Height Width of road 6 Meter to 7 Meter 9 Meter to 10.5 Meter 12 Meter to 14 Meter
Pole  arrangement Cut-off Type Semi Cutoff Type Cut-off Type Semi Cutoff Type Cut-off Type Semi Cutoff Type
8 Meter Single side 24 28
Staggered 24 28
Opposite 28 28
10 Meter Single side 30 30
Staggered 35 35 30 35
Opposite 35 40 30 35
12 Meter Single side 42 48 36 42
Staggered 36 42 36 42
Opposite 42 48 42 48



One Side
or Staggered
or Opposite
Street Intersection
Single Roadway Twin Roadways
(Median Mounting)
Street Intersections
Road Width up to 1.5 x Mounting Height Road Width beyond1.5 x Mounting Height Road Width up to 1.5x Mounting Height Road Width up to 2x Mounting Height Road Width up to 1.5x Mounting Height (each pavement) Width up to 2.0x Mounting Height
Types Types Type Type Types Types
II, III, IV III & IV II (4-way) I II & III I (4-way) & V


How to Design Efficient Street Lighting-Part-1


  • The basic idea of roadway and Highway lighting is to provide uniform level of illumination on road at horizontal and vertical level and provide a safe and comfortable environment for the night time driver.
  • Lighting design is basic idea of the selection and the location of lighting equipment to provide improved visibility and increased safety.
  • Street lighting systems should be designed in a way to avoid significant differences in luminance levels at the light source and on road areas. Furthermore, continuous variation of lighting levels can cause eye strain and should be avoided, in particular on long roads.
  • Road lighting provides visual conditions for safe, quick and comfortable movement of Road users.

Designing Factor for Street Light:

  • The factors that are playing a vital role in the Road Lighting are following.

(A) Type of Road

  • Road Classification

(B) Street Light Pole

  • Street Light Pole Arrangements
  • Placement of Pole

(C) Lighting Fixture

  • Lighting Fixture Mounting Height
  • Lighting Fixture Classification
  • Lighting Fixture Distributor

(D) Lighting Factors

  • Maintenance Factor
  • Coefficient of Utilization

(E) Lighting Uniformity

  • Lighting Uniformity
  • Surrounding Ratio

(F) Lighting Pollution

  • Glare
  • Sky Glow
  • Trespass

(G) Selection of Luminas

  • Type of Light
  • Watt
  • Lumen
  • CRI
  • Efficiency

(A) Classification As per Road:

Table 4 : Road Classes as per SP 72 (Part 8), IS 1944 (Part 1) and IS 1970

Class A1 Important routes with rapid and dense traffic where safety, traffic speed, and driving comfort are the main considerations
Class A2 Main Roads with considerable volume of mixed traffic, such as main city streets, arterial roads and thoroughfares.
Class B1 Secondary roads with considerable traffic such as main local traffic routes, shopping streets
Class B2 Secondary roads, with light traffic
Class C Lighting for residential and unclassified roads not included in previous groups
Class D Lighting for bridges and flyovers
Class E Lighting for town and city centers
Class F Lighting for roads with special requirement such as roads near air fields, railways and docks



A Heavy and high speed motorized traffic Road with fixed separators, No crossings for very long distance National highways or state highways or called interstate highways, express ways or motor ways
B Slightly lower density and lower speed traffic termed Road which is made for vehicular traffic with adjoining streets for slow traffic and pedestrians as we find in metros Trunk road or major road in a city
C Heavy and moderate speed traffic Important urban roads or rural roads. they do not interfere with the local traffic within the town Ring roads
D Slow traffic, pedestrians Linking to shopping areas and invariably the pedestrians, approach road Shopping street, trunk road
E Limited speed. Slow or mixed traffic predominantly pedestrians, Local streets, collectors road

(B) Street Light Pole:

(1) Street Light Arrangement:

  • There are four basic types of street lighting layout arrangements used for streets or highways illumination.
  • (a) One Side Pole Layout:
  • Arrangement: In One Side Pole Layout, all luminaries are located on one side of the road.
  • Road Width: For narrower roads.
  • Pole Height: The installation height of the lamp be equal to or less than the effective width of the road surface.

  • Advantage: There are good indelibility and low manufacturing cost.
  • Disadvantage: The brightness (illuminance) of the road on the side where the lamp is not placed is lower than the on which side the light pole is placed.

(b) Both Side Staggered Pole Layout:

  • Arrangement: In the staggered arrangement, the luminaires are placed alternately on each side of the road in a “zig-zag” or staggered fashion.
  • Road Width: For Medium Size roads.
  • Pole Height: The installation height of the lamp is equal or 1.5 time the effective width of the road.

  • Advantage: This type of arrangement is better than single side arrangement.
  • Disadvantage: Their longitudinal luminance uni­formity is generally low and creates an alternating pattern of bright and dark patches. However, during wet weather they cover the whole road better than single-side arrangements.

(c) Both Side opposite Pole Layout:

  • Arrangement:
  • In Both Side Opposite Pole Layout, the luminaries located on both sides of the road opposite to one another.
  • Road Width: For Medium Size roads.
  • Pole Height: The installation height of the lamp will be 2 to 2.5 time the effective width of the road.

  • Advantage: op­posite arrangements may provide slightly better lighting under wet conditions.
  • Disadvantage:
  • If the arrangement is used for a dual carriageway with a central reserve of at least one-third the carriageway with, or if the central re­serve includes other significant visual obstructions (such as trees or screens), it effectively becomes two single-sided arrangements and must be treated as such.

 (d) Twin-central Pole Layout:

  • Arrangement: In Twin central arrangement, the luminaries are mounted on a T-shaped in the middle of the center island of the road. The cen­tral reserve is not too wide, both luminaires can contribute to the luminance of the road surface on either lane.
  • Road Width: For Large Size roads.
  • Pole Height: The installation height of the lamp be equal to the effective width of the road.

  • Advantage: This arrangement generally more efficient than opposite arrangements. However, op­posite arrangements may provide slightly better lighting under wet conditions.

(2) Proper Placement of Pole:

(i) Setback

  • Set back is the horizontal distance between the face of a light pole and the edge of traveled way.
  • Placing luminaries too close to a vertical surface results in hotspots at its base.
  • A setback of 3 foot to 4 foot works well for many applications.
  • Light from luminaires at extremely short setbacks grazes the surface and enhances its texture.
  • Light from luminaries at Long setbacks (Luminaries too far from a vertical surface) cause shadows at low levels.
  • Longer setbacks may be required for taller surfaces.
  • Scallops between fixtures become more noticeable as setback increases.
  • As setback (or spacing) distance increases, Light levels and uniformity decrease.


Set Back (BS 5489)

Design Speed Pole Set Back
50 Km/Hr 0.8 Meter
80 Km/Hr 1 Meter
100 Km/Hr 1.5 Meter
120 Km/Hr 1.5 Meter


(ii) Overhang

  • Overhang is the horizontal distance between the center of a luminaries mounted on a bracket (Nadir) and the adjacent edge of a carriage way or traveled way.
  • In general, overhang should not exceed one fourth of the mounting height to avoid reduced visibility of curbs, obstacles, and footpaths.

(iii) Outreach

  • Outreach is the horizontal distance between the center of the column and the center of the luminaries and is usually determined for architectural aesthetic considerations.

(iv) Pole Boom(Arm) Length:

  • The use of an arm places the light source closer to the traveled way while allowing the pole to be located further from the edge of the traveled way.
  • Depending on the application, Pole arms may be single and/or double mast arms or davit arms at the top of the pole.
  • There are several different arm lengths and styles of arms that are used.

(v) Arm Type:

  • Type A bracket an arm has a single member arm. It is used when the Arm length is less than 3.5 Meter.
  • Type B bracket arm has a two member truss arm design. Type B arms are used when the Arm length is more than 3.5 Meter.

(vi) Arm Lengths:

  • The length of the bracket arm is dependent upon a street width, pole location in relation to the curb and the presence of a median.
  • Type A (Single member bracket) arms are available in 2 Meter and 2.5 Meter lengths.
  • Type B (Twin member bracket) arms are available in 3.5 Meter, 4 Meter and 5 Meter Lengths.
  • Pole Height is 10 Meter: On typical streets that are 12 Meter’ wide from curb to curb, either a 2 Meter or 2.5 Meter arm is used. Depending on whether the pole is located behind the sidewalk or in the grass parkway between the sidewalk and the curb, the arm length may need to be increased to 4 Meter.
  • Pole Height is 13 Meter: On an undivided street, generally Meter, 2.5 Meter or 4 Meter arms are used.
  • Pole Height is 13 Meter: divided Street, typically have a 8 Meter wide center median to divide opposing lanes of traffic. On streets where the light poles are installed in a raised median, two 4 Meter arms oriented 180° apart are used.

(vii) Boom Tilt Angle (Boom Angle)

  • When the angle of tilt is larger, a uniformity ratio is increasing. Otherwise discomfort glare is increasing because strong light comes into driver’s eyes. So the angle of tilt shall be kept from 15° to 30°.


Tilt Angle

Pole Height Arm Length Arm Tile Angle
6 Meter 0.5 Meter 5°,10°,15°
8 Meter 1 Meter 5°,10°,15°
10 Meter 1.5 Meter 5°,10°,15°
>=12 Meter 2 Meter 5°,10°,15°

(viii) Pole Height:

  • Light poles for conventional highway lighting applications support luminaire mounting heights ranging from approximately 30 ft to 50 ft (9.1 m to 15.2 m).
  • Light towers for high-mast lighting applications generally range from 80 ft to 160 ft (24.4 m to 48.8 m) and are designed in multiple sections.
  • Weathering steel is a common material choice for light towers.
  • Ornamental light Poles used for local streets generally range in height for 8 ft to 15 ft (2.4 m to 4.5 m).


Pole Height Application
< 6 Meter Majority of side streets or alleys, Public gardens and parking Area to make people feel safe
8 Meter Urban traffic route , the multiplicity of road junctions
10 Meter Urban traffic routes
12 Meter Heavily used routes
18 Meter High mast lighting poles shall be installed at large-scale area such as airports, dockyards, large industrial areas, sports areas and road Intersections.

 (ix) Poles distance from Curb (Offset):

  • The lighting poles should not be installed very close to the pavement edge, because the capacity of the roadway is decreased and the free movement of traffic is obstructed.
  • For roads with raised curbs (as in urban roads) =Min. 0.3 meter and desirable 0.6 meter from the edge of raised curb.
  • For roads without raised curbs (as in rural roads)=Min. 1.5 meter from the edge of the carriageway, subject to min. 5.0 meter from the center line of the carriageway.
  • Height and overhang of mounting
  • The glare on eyes from the mounted lights decreases with increases in the height of mounting. Usually, mounting height range from 6 to 10m.
  • Overhangs on the lighting poles would keep the poles away from the pavement edges, but still allow the lamp to be held above the curb or towards the pavements.

(x) Pole to Pole Spacing

  • Spacing is the distance, measured along the center line of the road, between successive luminaries in an installation.
  • To preserve longitudinal uniformity, the space height ratio should generally be greater than 3.
  • Placing luminaries too far apart creates scallops at the base of the surface.
  • Spacing distances that are equal to 3 to 4 times the setback work well for many applications.
  • Placing luminaries closer together eliminates scallops.
  • Uniformity and light levels increase as spacing (or setback) distances decrease.
  • Spacing of luminaires normally does not exceed five to six mounting heights.
  • The span must not be more than 45 meters and for an average of 20-30 meters.


Lighting Pole details as per Road

Road Road Width (Meter) Pole Arrangement Lamp (Watts) Pole to Pole Spacing (Meters) Mounting Height, (Meters) Arm Length, (Meters)
Expressway 10 Twin Central 250 25 To 35 12 1.5
15 250 20 To 35 12 3.0
20 Opposite 250 20 To 45 12 1.5
25 250 20 To 40 12 1.5
30 250 20 To 30 12 1.5
36 250 20 To 25 12 1.5
40 250 20 To 22 12 1.5
Major 10 One-side 250 10 To 40 10 1.5
15 250 10 To 45 12 3.0
10 Twin Central 150 20 To 37 10 1.5
15 250 20 To 43 12 3.0
20 Opposite 150 20 To 40 10 3.0
25 250 20 To 45 10 1.5
30 250 20 To 45 10 1.5
36 250 20 To 45 12 3.0
40 250 20 To 45 2 3.0
Collector 10 One-side 150 10 To 40 10 1.5
15 250 10 To 50 12 3.0
10 Twin Central 150 20 To 40 10 1.5
15 150 20 To 37 12 3.0
20 Opposite 150 20 To 47 10 1.5
25 250 20 To 48 10 1.5
8 One-side 150 10 To 38 8 1.5
10 150 10 To 37 8 3.0
15 150 15 To 38 10 3.0
10 Twin Central 150 20 To 45 10 3.0
15 150 20 To 39 12 3.0
20 1.5
Minor 4 One-side 70 10 To 40 8 1.5
6 70 10 To 40 8 1.5
8 70 10 To 40 8 1.5
10 70 10 To 39 8 1.5
10 Twin Central 70 20 To 35 8 1.5
15 Staggered 70 10 To 20 8 1.5
15 Opposite 70 20 To 40 8 1.5


Illumination Level

Classification  Average Illumination (lux) Ratio Minimum to average illumination
Class A1 30 0.4
Class A2 15 0.4
Class B1 8 0.3
Class B2 4 0.3


Relationship between Mounting Height and Spacing of Fixtures

Pole Arrangement Cut-off type Semi cutoff type
Height Spacing Height Spacing
Single side >=0.7 X Width of Road <=3 X Fixture Mounting Height >=0.8 X Width of Road <=3.5 X Fixture Mounting Height
Both Side Staggered >=1.5 X Width of Road <=3.5 X Fixture Mounting Height >=1.7 X Width of Road <=4 X Fixture Mounting Height
Both Side Opposite >=0.5 X Width of Road <=3 X Fixture Mounting Height >=0.6 X Width of Road <=3.5 X Fixture Mounting Height
Twin central >=0.7 X Width of Road <=3.5 X Fixture Mounting Height >=0.8 X Width of Road <=4 X Fixture Mounting Height


 Pole to Pole Distance vs Lux Level

Pole Height Lamp Pole to Pole Distance Max. Illumination (Lux) Average (Lux)
4 Meter 15 watt 12 to 18 Meter 25 18
5 Meter 18 watt 14 to 20 Meter 30 18
6 Meter 30 watt 18 to 24 Meter 32 20
7 Meter 50 watt 21 to 28 Meter 32 20
8 Meter 100 watt 24 to 32 Meter 40 22
9 Meter 110 watt 27 to 35 Meter 34 20
10 Meter 140 watt 30 to 40 Meter 35 22
12 Meter 180 watt 30 to 40 Meter 33 23
14 Meter 200 watt 30 to 40 Meter 30 21


Lux Vs Mounting Height

Fixtures (Lux) Mounting Height
3000 to 10000 Lux 6 to 7 Meter
10000 to 20000 Lux 7 to  9 Meter
More than 20000 Lux More than 9 Meter


Road – Pole Details

Road Road Type Type of Pole positions Individual Carriageway Width (Meter) Central Verge (Meter) Pole Height above Ground (Meter) Maximum Pole to Pole Spacing (Meter) Clearance from Road Edge (Meter) Bracket Length (Meter) Tilt Angle Lighting Specifications Lamp (Watt)
A1 Dual Carriage Central Verge 10 1.2 12 40 0.6 1 meter  10° 35 lux
/0.4/ 0.33
HP SV 400W
A1 Dual Carriage Central Verge 11 1.2 12 40 0.6 1 meter  10° 35 lux
/0.4/ 0.33
HP SV 400W
A1 Dual Carriage Central Verge 12 1.2 12 40 0.6 1 meter  10° 35 lux
/0.4/ 0.33
HP SV 400W
A1 Dual Carriage Central Verge 14 1.2 12 40 0.6 1 meter  10° 35 lux
/0.4/ 0.33
HP SV 400W
A1 Dual Carriage Central Verge 16 1.2 12 40 0.6 1 meter  10° 35 lux
/0.4/ 0.33
HP SV 400W
A1 Single Carriage Opposite 12 0 12 35 0.6 1 meter  10° 35 lux
/0.4/ 0.33
HP SV 250W
A1 Single Carriage Opposite 14.5 0 12 35 0.6 1 meter  10° 35 lux
/0.4/ 0.33
HP SV 250W
A1 Single Carriage Opposite 16 0 12 40 0.6 Around one meter  10° 35 lux
/0.4/ 0.33
HP SV 400W
A1 Single Carriage Opposite 18 0 12 40 0.6 1 meter  10° 35 lux
/0.4/ 0.33
HP SV 400W
A1 Single Carriage Opposite 21 0 12 40 0.6 1 meter  10° 35 lux
/0.4/ 0.33
HP SV 400W
Single Carriage Opposite 25 0 12 40 0.6 1 meter  10° 35 lux
/0.4/ 0.33
HP SV 400W
A1 Single Carriage Opposite 31 0 12 40 0.6 1 meter  10° 35 lux/ 0.4/
HP SV 400W
A2 Single Carriage Single Sided 10 11 30 0.6 < 1.0 meter  10° 25 lux
/0.4/ 0.33
HP SV 250W
A2 Single Carriage Single Sided 9 11 30 0.6 < 0.5 meter  10° 25 lux
/0.4/ 0.33
HP SV 250W
A2 Single Carriage Single Sided 7 11 30 0.6 < 0.5 meter  10° 25 lux
/0.4/ 0.33
HP SV 250W
A2 Single Carriage Single Sided 7 11 30 0.6 < 0.5 meter  10° 25lux
/0.4/ 0.33
HP SV 250W
A3 Single Carriage Single Sided 7 8 20 0.6 < 0.5 meter  10° 20lux
HP SV 150W
Pedestrian Pathway Single Carriage Single Sided 3m-6m 7.5 20-25 0.6 <0.5 meter  10° 20 lux
HP SV 150W


Pole Data

Poles (Meter) Top Dia (mm) Bottom Dia (mm) Thickness (mm) Base plate (mm) Single Arm Bracket (mm) Double Arm Bracket (mm)
3 70 130 3 200x200x12 1000 NA
3 70 130 3 200x200x12 NA 1000
4 70 130 3 200x200x12 1000 NA
4 70 130 3 200x200x12 NA 1000
4 70 130 3 200x200x12 1000 NA
5 70 130 3 200x200x12 NA 1000
5 70 130 3 200x200x12 1000 NA
6 70 130 3 200x200x12 NA 1000
6 70 130 3 200x200x12 1000 NA
7 70 135 3 225x225x16 1000 NA
7 70 135 3 225x225x16 NA 1000
8 70 135 3 225x225x16 1000 NA
8 70 135 3 225x225x16 NA 1000
9 70 155 3 260x260x16 1000 NA
9 70 155 3 260x260x16 NA 1000
9 70 175 3 275x275x16 1000 NA
9 70 175 3 275x275x16 NA 1000
10 70 175 3 275x275x16 1000 NA
10 70 175 3 275x275x16 NA 1000
10 70 200 3 290x290x16 1000 NA
10 70 200 3 290x290x16 NA 1000
11 70 210 3 320x320x20 1000 NA
11 70 210 3 320x320x20 NA 1000
12 70 230 3 325x325x20 1000 NA
12 70 230 3 325x325x20 NA 1000


Recommended Levels of Illumination (BIS 1981) (IS 1944)

Type of Road Road Characteristics Road Width (Meter) Average Level of Illumination on Road Surface in Lux Ratio of Minimum/Average Illumination Ratio of Minimum/Max Illumination Type of Luminaire Preferred Luminas Mounting Height
A-1 Important traffic routes carrying fast traffic >10.5,12,14,16,18,20,30 30 0.4 33 Cutoff 9 To 10 Meter
A-2 Main roads carrying mixed traffic like city main roads/streets, arterial roads, throughways > 7 m up to 10 m 15 0.4 33 Cutoff 9 To 10 Meter
B-1 Secondary roads with considerable traffic like local traffic routes, shopping streets < 7m Colony Roads 8 0.3 20 Cutoff or semi-cutoff 7.5 To 9 Meter
B-2 Secondary roads with light traffic 4m,5m, 6m 4 0.3 20 Cutoff or semi-cutoff 7.5 To 9 Meter

Quick Reference Lighting Power Densities


Lighting Power Densities for Building Exteriors

ASHRAE 90.1-2004, Table 9.4.5

Tradable Surfaces LPD

Uncovered Parking Areas –Parking Lots and drives

0.15 W/ft²

Building Grounds –Walkways less than 10 feet wide

1.0 W/linear foot

Building Grounds –Walkways 10 feet wide or greater; Plaza areas; Special Feature Areas

0.2 W/ft²

Building Grounds –Stairways

1.0 W/ft²
Building Entrances and Exits –Main entries

30 W/linear foot of door width

Building Entrances and Exits –Other doors

20 W/linear foot of door width

Canopies and Overhangs –free standing and attached

1.25 W/ft²

Outdoor Sales –Open areas (including vehicle sales lots)

0.5 W/ft²
Outdoor Sales –Street frontage for vehicle sales lots in addition to “open area” allowance

20 W/linear foot


Lighting Power Density


Building Area Type

LPD (W/m2)
Automotive Facility


Multifamily Residential


Convention Centre



Dining : Bar Lounge/ Leisure



Dining : Cafeteria/ Fast Food


Parking Garage

Dining : Family


Performing Arts Theatre

Dormitory/ Hostel


Police/ Fire Station



Post Office/ Town Hall

Health care-Clinic


Religious Building

Hospital/ Health Care


Retail/ Mall



School/ University



Sports Arena

Manufacturing Facility





Motion Picture Theatre






Interior Lighting Power Space Density As per  Function Method


Building Area Type

LPD (W/m2)


Office-open plan

Conference/ Meeting/ Multipurpose


Classroom/Lecture/ Training



• For Hotel


• For Performing Arts Theatre


• For Motion Picture Theatre


Audience/ Seating Area


• For Gymnasium

• For Convention Centre


• For Religious Buildings

• For Sports Arena


• For Performing Arts Theatre


• For Motion Picture Theatre

• For Transportation


Atrium-first three floors


Atrium-each additional floor

Lounge/ Recreation


• For Hospital

Dining Area


• For Hotel

• For Motel


• For Bar Lounge/ Leisure Dining

• For Family Dining


• Food Preparation





Dressing/ Lockers/ Fitting Room

Corridor/ Transition


• For Hospital

• For Manufacturing facility




Active Storage


• For Hospital


Inactive Storage

• For Museum


Electrical/ Mechanical Facility

For Indoor Field Area



• For Fine Material Storage


• For Medium/ Bulky Material





Convention Centre – Exhibit Space



• For Card File & Cataloguing


• For Stacks

• For Reading Area



• For Emergency


• For Recovery


• For Nurse Station


• For Exam Treatment


• For Pharmacy

• For Patient Room


• For Operating Room

• For Nursery


• For Medical Supply

• For Physical Therapy


• For Radiology

• For Laundry – Washing


Automotive – Service Repair Manufacturing Facility

• For Low Bay (<8m ceiling)


• For High Bay (>8m ceiling)

• For Detailed Manufacturing


• For Equipment Room

• For Control Room


Hotel/ Motel Guest Rooms

Dormitory – Living Quarters



• For General Exhibition


• For Restoration

Bank Office – Banking Activity Area



• For Sales Area


• For Mall Concourse


Sports Arena

• For Rising Sports Area

• For Court Sports Area


Parking Garage – Garage Area


• For Airport – Concourse

• For Air/ Train/ Bus-Baggage Area


• For Ticket Counter Terminal



Exterior Lighting Power Space Density


Exterior Lighting Applications Power Limits
Building entrance (with canopy) 13 W/m2 of canopied area
Building entrance (without canopy) 90 W/linear meter of door width
Building exit 60 W/linear meter of door width
Building facades 2 W/m2 of vertical facade area2




Lighting Power Densities for Buildings Except Low-Rise Residential Buildings

ANSI/ASHRAE/IES Standard 90.1-2010: Table 9.6.11

Common  Space Type LPD (W/ft²)
Conference/Meeting/Multipurpose 1.23
Corridor/Transition 0.66
Dining Area 0.65
Electrical/Mechanical 0.95
Food Preparation 0.99
Lobby 0.99
Lobby for Elevator 0.64
Lounge/Recreation 0.73
Office: Enclosed 1.11
Office: Open Plan 1.11
Restrooms 0.98
Stairway 0.69
Storage 0.63
Workshop 1.59


Lighting Power Densities Using the Building Area Method


Building Area Type LPD
Automotive facility 0.82W/ft2
Convention center 1.08W/ft2
Courthouse 1.05W/ft2
Dining: bar lounge/leisure 0.99W/ft2
Dining: cafeteria/fast food 0.90W/ft2
Dining: family 0.89W/ft2
Dormitory 0.61W/ft2
Exercise center 0.88W/ft2
Fire station 0.71W/ft2
Gymnasium 1.00W/ft2
Health-care clinic 0.87W/ft2
Hospital 1.21W/ft2
Hotel 1.00W/ft2
Library 1.18W/ft2
Manufacturing facility 1.11W/ft2
Motel 0.88W/ft2
Motion picture theater 0.83W/ft2
Multifamily 0.60W/ft2
Museum 1.06W/ft2
Office 0.90W/ft2
Parking garage 0.25W/ft2
Penitentiary 0.97W/ft2
Performing arts theater 1.39W/ft2
Police station 0.96W/ft2
Post office 0.87W/ft2
Religious building 1.05W/ft2
Retail 1.40W/ft2
School/university 0.99W/ft2
Sports arena 0.78W/ft2
Town hall 0.92W/ft2
Transportation –Airport 0.77W/ft2
Warehouse 0.66W/ft2
Workshop 1.20 W/ft2


Maximum Illumination Power Densities    

Building Code of Australia (BCA)

Lux Level of Rooms LPD
< 80 Lux: 7.5 Watt/M2
80 To 160 Lux 9 Watt/M2
160 To 240 Lux 10 Watt/M2
240 To 320 Lux 11 Watt/M2
320 To 400 Lux 12 Watt/M2
400 To 480 Lux 13 Watt/M2
480 To 540 Lux 14 Watt/M2
540 To 620 Lux 15 Watt/M2



Building Code of Australia (BCA)

Space LPD
Auditorium, church and public hall 10 Watt/M2
Boardroom and conference room 10 Watt/M2
Carpark – general 6 Watt/M2
Carpark – entry zone (first 20m of travel) 25 Watt/M2
Common rooms, spaces and corridors in a Class 2 building 8 Watt/M2
Control room, switch room, and the like 9 Watt/M2
Corridors 8 Watt/M2
Courtroom 12 Watt/M2
Dormitory of a Class 3 building used for sleeping only 6 Watt/M2
Dormitory of a Class 3 building used for sleeping and study 9 Watt/M2
Entry lobby from outside the building 15 Watt/M2
Health-care – children’s ward 10 Watt/M2
Health-care – examination room 10 Watt/M2
Health-care – patient ward 7 Watt/M2
Health-care – all patient care areas including corridors 13 Watt/M2
Kitchen and food preparation area 8 Watt/M2
Laboratory – artificially lit to an ambient level of 400 lx or more 12 Watt/M2
Library – stack and shelving area 12 Watt/M2
Library – reading room and general areas 10 Watt/M2
Lounge area for communal use in a Class 3 building or Class 9c 10 Watt/M2
Museum and gallery – circulation, cleaning and service lighting 8 Watt/M2
Office – artificially lit to an ambient level of 200 lx or more 9 Watt/M2
Office – artificially lot to an ambient level of less than 200 lx 7 Watt/M2
Plant room 5 Watt/M2
Restaurant, Cafe, bar, hotel lounge and a space for the serving of food or drinks 18 Watt/M2
Retail space including a museum and gallery whose purpose is the sale of objects 22 Watt/M2
School – general purpose learning areas and tutorial rooms 8 Watt/M2
Sole-occupancy unit of a Class 3 building 5 Watt/M2
Sole-occupancy unit of a Class 9c building 7 Watt/M2
Storage with shelving no higher than 75% of the height of the aisle lighting 8 Watt/M2
Storage with shelving higher than 75% of the height of the aisle lighting 10 Watt/M2
Service area, cleaner’s room and the like 5 Watt/M2
Toilet, locker room, staff room, rest room and the like 6 Watt/M2
Wholesale storage and display area 10 Watt/M2



Building Code of Australia (BCA)

Illumination LPD (Watt/M2)
Rooms to achieve
<80 lux 7.5
80 – 160 lux 9
160 – 240 lux 10
240 – 320 lux 11
320 – 400 lux 12
400 – 480 lux 13
480 – 540 lux 14
540 – 620 lux 15
>620 lux 80


Recommended LPD for Buildings


Building Area LPD (Watt/M2)
Automotive Facility 9.7
Convention Center 12.9
Dining: Bar Lounge/Leisure 14.0
Dining: Cafeteria/Fast Food 15.1
Dining: Family 17.2
Dormitory/Hostel 10.8
Gymnasium 11.8
Healthcare-Clinic 10.8
Hospital/Health Care 12.9
Hotel 10.8
Library 14.0
Manufacturing Facility 14.0
Motel 10.8
Motion Picture Theater 12.9
Multifamily Residential 7.5
Museum 11.8
Office 10.8
Parking Garage 3.2
Performing Arts Theatre 17.2
Police/Fire Station 10.8
Post Office/Town Hall 11.8
Religious Building 14.0
Retail/Mall 16.1
School/University 12.9
Sports Arena 11.8
Transportation 10.8
Warehouse 8.6
Workshop 15.1


Lighting Power Density

BEC-Table 5.4

Building Area LPD (Watt/M2)
Atrium / Foyer with headroom over 5m 17
Bar / Lounge 14
Banquet Room / Function Room / Ball Room 20
Canteen 11
Car Park 5
Classroom / Training Room 12
Clinic 15
Computer Room / Data Centre 15
Conference / Seminar Room 14
Corridor 8
Court Room 15
Dormitory 8
Entrance Lobby 14
Exhibition Hall / Gallery 17
Guest room in Hotel or Guesthouse 13
Gymnasium / Exercise Room 13
Kitchen 13
Laboratory 15
Lecture Theatre 13
Library – Reading Area, Stack Area or Audio Visual Centre 15
Lift Car 11
Lift Lobby 11
Loading & Unloading Area 8
Office, enclosed (Internal floor area at or below 15m2) 13
Office, open plan or with internal floor area above 15m2 12
Passenger Terminal Building 14
Arrival Hall /Departure Hall with headroom not exceeding 5m 18
Arrival Hall / Departure Hall with headroom over 5m 13
Passenger circulation area
Patient Ward / Day Care 15
Plant Room / Machine Room / Switch Room 10
Public Circulation Area 13
Railway Station
Concourse / Platform / Entrance / Adit / Staircase, with headroom not exceeding 5 m 14
Concourse / Platform / Entrance / Adit / Staircase, with headroom over 5 m 18
Refuge Floor 11
Restaurant 17
Retail 17
School hall 14
Seating Area inside Theatre / Cinema /Auditorium / Concert Hall / Arena 10
Server Room / Hub Room 10
Sports Arena, Indoor, for recreational purpose 17
Staircase 7
Storeroom / Cleaner 9
Toilet / Washroom / Shower Room 11
Workshop 13


Lighting Power Densities


Building Area Type LPD (W/m2) LPD (W/m2)
Atrium (First 40 ft in height ) 0.03
Atrium (Above 40 ft in height ) 0.02
Audience/Seating Area
Permanent  For auditorium 0.79
For Performing Arts Theater 2.43
For Motion Picture Theater 1.14
Classroom/Lecture/Training 1.24
Conference/Meeting/Multipurpose 1.23
Corridor/Transition 0.66 Width<8 ft
Dining Area 0.65
For Bar Lounge/Leisure Dining 1.31
For Family Dining 0.89
Dressing/Fitting Room for Performing Arts Theater 0.40
Electrical/Mechanical 0.95
Food Preparation 0.99
For Classrooms                               1.28
For Medical/Industrial/Research 1.81
Lobby 0.90
For Elevator 0.64
For Performing Arts Theater 2.00
For Motion Picture Theater 0.52
Locker Room 0.75
Lounge/Recreation 0.73
Enclosed 1.11
Open Plan 0.98
Restrooms 0.98
Sales Area 1.68
Stairway 0.69
Storage 0.63
Workshop 1.59
Service/Repair 0.67
Banking Activity Area 1.38
Convention Center
Audience Seating 0.82
Exhibit Space 1.45
Courthouse/Police Station/Penitentiary
Courtroom 1.72
Confinement Cells 1.10
Judges’ Chambers 1.17
Penitentiary Audience Seating 0.43
Penitentiary Classroom 1.34
Penitentiary Dining 1.07
Living Quarters 0.38
Fire Stations
Engine Room 0.56
Sleeping Quarters 0.25
Gymnasium/Fitness Center
Fitness Area 0.72
Gymnasium Audience Seating 0.43
Playing Area 1.20
Corridor/Transition Width < 8 ft 0.89
Emergency 2.26
Exam/Treatment 1.66
Laundry/Washing 0.60
Lounge/Recreation 1.07
Medical Supply 1.27
Nursery 0.88
Nurses’ Station 0.87
Operating Room 1.89
Patient Room 0.62
Pharmacy 1.14
Physical Therapy 0.91
Radiology/Imaging 1.32
Recovery 1.15
Hotel/Highway Lodging
Hotel Dining 0.82
Hotel Guest Rooms 1.11
Hotel Lobby 1.06
Highway Lodging Dining 0.88
Highway Lodging Guest Rooms 0.75
Card File and Cataloging 0.72
Reading Area 0.93
Stacks 1.71
Corridor/Transition Width < 8 ft 0.41
Detailed Manufacturing 1.29
Equipment Room 0.95
Extra High Bay (>50 ft Floor to Ceiling Height) 1.05
High Bay (25–50 ft Floor to Ceiling Height) 1.23
Low Bay (<25 ft Floor to Ceiling Height) 1.19
General Exhibition 1.05
Restoration 1.02
Parking Garage
Garage Area 0.19
Post Office
Sorting Area 0.94
Religious Buildings
Audience Seating 1.53
Fellowship Hall 0.64
Worship Pulpit, Choir 1.53
Dressing/Fitting Room 0.87
Mall Concourse 1.10
Sales Area (for accent lighting) 1.68
Sports Arena
Audience Seating 0.43
Court Sports Arena—Class 4 0.72
Court Sports Arena—Class 3 1.20
Court Sports Arena—Class 2 1.92
Court Sports Arena—Class 1 3.01
Ring Sports Arena 2.68
Air/Train/Bus—Baggage Area 0.76
Airport—Concourse 0.36
Audience Seating 0.54
Terminal—Ticket Counter 1.08
Fine Material Storage 0.95
Medium/Bulky Material Storage 0.58




Calculation of Crippling (Ultimate Transverse) Load on Electrical Pole

Calculation of Crippling (Ultimate Transverse) Load on Electrical Pole

  • Wind Speed = 89 Mile/Hr.
  • Height of Pole=10 Meter
  • Type of Pole =RCC
  • Height of Pole in Ground=1.5 Meter.
  • Pole Section on Bottom of Pole (Length x Width)=400mm x 150mm
  • Pole Section on Top of Pole (Length x Width)=127mm x 150mm
  • Conductor Mounting from top of Pole(g)=0.5 Meter.
  • Distance between Two Pole(s) =20 Meter.
  • No of Conductor on Pole(n)=3No’s
  • Size of Conductor(r)= 30mm


  • Wind Pressure = 00256 x 2x Wind Speed
  • Wind Pressure = 00256 x 2x 90 = 20.506 Pound /Sq.Foot
  • Wind Pressure(Wp) =4.882×20.506 = 100 Kgf/M2
  • Wind Load on Conductor/Span(ws)=2/3 x Wp x s x r x n
  • Wind Load on Conductor/Span(ws)=2/3 x 100 x 20 x 30 x 3 =120 Kg———–(I)
  • Height of Pole Above Ground (h)= 10-1.5 =8.5 Meter
  • Total Bending Movement at Ground Level due to Wind Load on All Conductor=ws x h
  • Total Bending Movement at Ground Level due to Wind Load on All Conductor(b)=120 x 8.5= 960 Kg.Mt
  • Equivalent Safe Working Load at said Meter from TOP of The Pole corresponding to Wind Load on All Conductors =b / (h- g) = 960 / 8.5-0.5 =120 Kg
  • Wind Load on Pole Surface above Ground Level (p1)=Wp x h /((l1+w1)/(2×1000))
  • Wind Load on Pole Surface above Ground Level (p1)=100×8.5/(400+150/2×1000) =233.75 Kg
  • Centre of Gravity of Tapering rectangular section of Pole(p2)= (h/3)x((l2+(l1*2))/(l1+l2))
  • Centre of Gravity of Tapering rectangular section of Pole(p2)= (5/3)x((127+(400×2)) /(127+400))=4.98Mt
  • Bending Movement at Ground Level due to Wind Load on Pole(p) =p1 x p2
  • Bending Movement at Ground Level due to Wind Load on Pole(p) =233.75×4.98=1164.98 Kg.Mt
  • Equivalent Safe Working Load at said meter from Top of The Pole corresponding to Wind Load on Pole(wt) = p /(h-g) =1164.98 / (8.5-0.5) = 62 Kg——————————(II)
  • Total Transverse Load at said meter from Top of The Pole (Due to wind Load on Conductors + Wind Load on Pole Surface) (T)=Ws + Wt = 120+145.62 =256.62 Kg
Type of Pole Safety Factor
Wooden Pole 3.5
RCC Pole 2.5
PCC Pole 2.5
Steel Tubular Pole 2
Rail/RSJ Pole 2
Struts (Steel Pole) 2.5
Struts (RCC/PCC) 3
PCC Pole for 33 KV 2


  • From Above Table Safety Factor=2.5
  • Total Transverse Load (Crippling Load) of Pole = T x Safety Factor
  • Total Transverse Load (Crippling Load) of Pole = 256 x 2.5 =664 Kg.
  • Total Transverse Load (Crippling Load) of Pole=664 Kg
Max. Length of Pole (Meter) Min. Ultimate Transverse Load from 0.6meter from Top (Kg)
17 3000
17 2300
17 2000
17 1400
16 1100
15 1050
14 1050
13 1000
12 800
11 600
10 500
9 300
8 200
7 200
6 200
5 150
4 150
3 150


  • From Above Table Min. Ultimate Transverse Load for 10 Meter Pole = 500 Kg and as per our calculation it is 664 Kg hence Selection of Pole if O.K


  • Calculated Transverse Load (Crippling Load) of Pole = 664 Kg

Various Factors for Illumination Calculations


  • Interior and exterior lighting design requires a reasonable uniform illuminance in all working areas.
  • There are two important factors in the planning or designing of lighting Scheme.
  • (1) Maintenance factors (MF)
  • (2) Utilization factor (UF)
  • The illuminance and luminance levels in a lighting installation do not remain constant over its period of operation. Over time, they decrease due to degradation and failure of light sources, soiling of lamps and luminaires due to the reduced reflectance values of the room surfaces. At g planning stage these factors need to be consider in the head of maintenance factor.
  • The right selection of maintenance factor for each lighting calculation at planning stage is depend upon some details like Type of Lighting Fixtures and Lamp, the environmental information , the cleaning intervals, Total Working Hours.
  • The Lighting Scheme may be satisfactory, economical, safe, colorful, effective, comfortable and energy efficient by choosing proper maintenance factor and utilization factor.

Importance of Maintenance Factor and Utilization Factor:

  • By choosing Constant M.F & U.F for any Project (Cost of Project)
  • We normally choose 0.8 as a Maintenance factor as a useful rule of thumb.
  • There is no reason why we choose M.F as 0.8 on every lighting installation project. Every project is different so the maintenance factor should be derive according to the circumstances and the lighting technology being used.
  • The Location and environment Condition (Cost and Life of Luminar):
  • The location where the luminaires is very important and which have an effect on light levels.
  • For close area like in industrial warehouse and in office we may select open type and without waterproof Lighting Fixtures.
  • For open Area, we should select close and waterproof fixtures.
  • Environment condition (Pollution, Clean) should effect on light levels hence directly effect on number of luminaire and space of luminar which effect Cost of Luminar.
  • For very long service life this criteria is impact on the overall maintenance factor.
  • Service life (Energy use and Cost)
  • It is very important to decide the service life of Luminar in calculations because it will lead to decisions on the initial light level and the number of installed luminaires.
  • This will mainly affect the amount of lighting required  and therefore have an impact on both capital and operational costs.
  • More Lights and Over Spacing (More Energy Bills)
  • The MF has a great impact on energy efficiency. If we select too much lighting in designing lighting project due to inaccurate maintenance factors, then the we will pay more electricity bills for that.
  • The products availability and Operating Time (Project Cost)
  • The correct maintenance factor for a lighting project has other benefits in terms of planning.
  • If we plan a 50,000-hour life in their lighting system (for 10Years of operation), But we use Luminars only a 7 years due to lease for an office space.
  • By changing this value, the LLMF will be changed and the amount of light and number of luminaires could be greatly reduced. This will save the money in the short and long-term.

Numbers of Factors for Illumination Calculation:

  • There are mainly below two Factors which are important while we design Illumination.
  • Utilization Factor (UF)
  • Maintenance Factor (MF)
  • Equation for Required Illumination is
  • E = N (n x φ) x MF x UF / A
  • N =( E x A) / MF x UF x (φx n)
  • Where:
  • N = Number of luminaires required
  • E = Maintained Illuminance (lux)
  • φ = Initial lamp output (lumens)
  • n = Number of lamps in luminaire
  • MF = Maintenance factor (sometimes also called light loss factor LLF)
  • UF = Utilization factor
  • A = Area of room (m2)


  • The light flux reaching at the working plane is always less than the lumen output of the lamp due to some of the light is absorbed by the various surface textures.
  • Utilization Factor is Proportion of light reaching working plane to the light output of lamps.
  • UF = Lumens received on Working Plan / Lumens output of luminaires
  • The lighting manufacturers’ catalogues give Utilization Factors for standard conditions.
  • The UF is expressed as a number which is always <1.
  • A typical value might be 0.9 for a modern office building.
  • The Utilization Factor takes the account of Room Reflectance, Room shape, Polar distribution and Light output ratio of the fitting
  • Brighter colors with high reflectance result in a higher UF.
  • A high UF means Less Nos of lamps are required resulting in a more energy efficient light design.
  • Utilization Factor mainly depends on
  • (1) Type of light, light fitting.
  • (2) Color surface of walls and ceiling.
  • (3) Mounting height of lamps.
  • (4) Area to be illuminated.
  • (5) Room Index (Area and Mounting Height)
  • Room Surface Reluctance:
  • To determine the UF from the luminaire data sheet it is necessary to know the average room surface reflectance.
  • The ceiling is normally considered to be light in color and an average value of 70% (or 0.7) is normally used.
  • The Floor is usually considered to be dark and an average value of 20% (or 0.2) is normally used.
  • The walls, however, can vary from light to dark depending on the wall surface colors. Luminaire manufacturers usually provide UFs for three average wall reflectance of 50%, 30% and 10%. A value of 50% applies to walls of light decor, 30% moderate decor and 10% dark decor.

Table 1.7 Typical Reluctance Factors




80% To 85%

Light gray

45% To 70%

Dark gray

20% To 25%

Ivory white

70% To 85%


60% To 70%

Pearl gray

70% To 75%


40% To 70%


30% To 50%


20% To 40%


25% To 50%


20% To 30%

Azure blue

35% To 40%

Sky blue

35% To 40%


50% To 70%

Cardinal red

20% To 25%


20% To 40%

 Space Height Ratio (SHR):

  • The ratio of Distance between two luminaire centers, in a regular square array of luminaires, divided by their height above the working plane.
Direct Concentrating 0.40
Direct Spreading 1.20
Direct Indirect Diffusing 1.30
Semi-direct-Indirect 1.50
  •  Room Index (RI):
  • This takes account of room proportions and height of the luminaire above the working plane.
  • It is used to determine the Utilization factor.
  • I. = L x W / (L + W) Hm
  • where
  • L = Length
  • W = Width
  • Hm = Height of luminaire above working plane. 
Utilization factor
Room Reflectance Room Index
Ceiling Wall Floor 0.75 1 1.25 1.5 2 2.5 3 4 5
0.7 0.5 0.2 0.43 0.49 0.55 0.6 0.66 0.71 0.75 0.8 0.83
0.7  0.3 0.2  0.35 0.41 0.47 0.52 0.59 0.65 0.69 0.75 0.78
0.7  0.1 0.2  0.29 0.35 0.41 0.46 0.53 0.59 0.63 0.7 0.74
0.5 0.5 0.2 0.38 0.44 0.49 0.53 0.59 0.63 0.66 0.7 0.73
 0.5 0.3 0.2  0.31 0.37 0.42 0.46 0.53 0.58 0.61 0.66 0.7
0.5  0.1 0.2  0.27 0.32 0.37 0.41 0.48 0.53 0.57 0.62 0.66
0.3 0.5 0.2 0.3 0.37 0.41 0.45 0.52 0.57 0.6 0.65 0.69
0.3  0.3 0.2  0.28 0.33 0.38 0.41 0.47 0.51 0.54 0.59 0.62
0.3  0.1 0.2  0.24 0.29 0.34 0.37 0.43 0.48 0.51 0.56 0.59
0 0 0 0.19 0.23 0.27 0.3 0.35 0.39 0.42 0.46 0.48

 (2) Maintenance factor (MF) / (Light Loss factor LLF):

  •  The Light Loss Factor has been replaced by maintenance factor in the 1994 CIBSE Guide.
  • Previously LLF and MF are differently mentioned but there is no account of the lamp lumen maintenance factor (LLMF).
  • In the 1994 Guide, maintenance factor (MF), LLMF and LSF are mention.
  • MF = RSMF x LMF x LLMF x LSF
  • Lamp Lumen Maintenance Factor (LLMF) decrease in luminous flux as per aging of the light source.
  • Lamp Survival Factor (LSF) takes into account the lamp’s service life without immediate replacement.
  • Luminaire Maintenance Factor (LMF) decrease in the output of the luminaires due to pollution.
  • Room Surface Maintenance Factor (RSMF) soiling or dusting in the Room space.
Quick Consideration of Maintenance factor
Room Classification Lamp Maintenance Factor Maintenance Factor for dirty lamp Total Maintenance Factor
Very clean 0.09 0.85 0.9
Clean 0.9 0.9 0.8
Average 0.9 0.8 0.7
Dirty 0.9 0.7 0.6


Environment Activity or Task Area

Very Clean Clean rooms, semiconductor plants, hospital clinical areas, computer centers
Clean Offices, schools, hospital wards
Normal dirty Dirty Shops, laboratories, restaurants, warehouses, assembly areas, workshops

Steelworks, chemical works, foundries, welding, polishing, woodwork


Quick Consideration of Maintenance Factor
Enclosed fixture, clean room 0.80
Average conditions 0.70
Open fixture or dirty room 0.60

 (A) Room Surface Maintenance Factor (RSMF): (dirt on the surfaces of the room)

  • It takes account of the effect of dirt and dust accumulation and other degradation of the reflectivity of the room surfaces.
  • The room surface maintenance factor is the ratio of the room surfaces reflectance before and after cleaning.
  • It depends highly on the conditions in a room like very clean, clean, dirty or very dirty.
  • The more dirty the room, the lower the maintenance factor.
  • RSMF is depending upon Room Surface Cleaning.
  • RSMF does not depend on LMF and LLMF.

Room Surface Maintenance Factor (Annual Clean) – RSMF

Type of Room

1 Year Room Clean

3 Year Room Clean

Direct Luminaires Direct /Indirect Luminaires Direct Luminaires Direct /Indirect Luminaires

Very Clean

0.97 0.96 0.97



0.95 0.91 0.94



0.91 0.84 0.9



0.86 0.75 0.86


(B) Lamp Lumen Maintenance Factor (LLMF): (Lamp Aging)

  •  The lamp lumen maintenance factoris the ratio of light output of a lamp, after a specified number of hour’s operation, to the initial light output of the lamp.
  • It is describing the ageing of the lamp or the reduction of light intensity over time. Manufacturers offer comprehensive tables about their lamps luminous flux behavior.
  • Lamp Lumen Maintenance Factor takes accounts the effect of the decrease in Lumen of the light sources during its Life time Operation.
  • The LLMF expresses the usual reduction of the luminosity over the lifetime, e.g. by a factor of 0.92 after 2000 hours. After 2,000 hours the illuminant still emits 92% of the luminosity when new.
  • The lamp lumen maintenance factor considers the average decrease in luminous flux of the light source
Lamp Lumen Maintenance Factors (LLMF)
Lamp Type Operating Hours
4000 Hr. 6000 Hr. 8000 Hr. 10000 Hr. 12000 Hr.
High Pressure Sodium 0.98 0.97 0.94 0.91 0.9
Metal Halide 0.82 0.78 0.76 0.74 0.73
High Pressure Mercury 0.87 0.83 0.8 0.78 0.76
Low Pressure Sodium 0.98 0.96 0.93 0.9 0.87
Tubular Fluorescent 0.95 0.94 0.93 0.92 0.91
Compact Fluorescent 0.91 0.88 0.86 0.85 0.84

(C) Luminaire Maintenance Factors (LMF): (Dirt on lamp)

  • The luminaire maintenance factor is the ratio of the luminaires luminous flux before and after cleaning.
  • It depends on the luminaire construction and design (open housing or closed one) as well as on environmental conditions (dirty or clean).
  • The higher the luminaires protection degree from dust, and the cleaner the room, the higher the maintenance factor.
  • LMF is depending upon Type of Laminar, Location and Frequency of cleaning.
  • LMF Luminaire Maintenance Factor takes account of the effect of dust and dirt accumulation on the luminaire.
  • Luminaires are classified according to their degree of sealing and their distribution, obviously dust accumulation on an open up light is far more onerous than on a sealed downlight.
  • Dust and dirt build up on the rear Heatsink Increases LED temperature, lowers output and effects life


Luminar Maintenance Factor (LMF)
Type of Distribution Environment Condition Expose Time
1 Year 2 Year 3 Year 4 Year 5 Year 6 Year
Open Distribution Very Clean 0.96 0.94 0.92 0.9 0.88 0.87
Clean 0.93 0.89 0.85 0.82 0.79 0.77
Normal 0.89 0.84 0.79 0.75 0.7 0.67
Dirty 0.83 0.78 0.73 0.69 0.65 0.62
Direct Distribution Very Clean 0.95 0.92 0.89 0.86 0.84 0.82
Clean 0.9 0.84 0.79 0.74 0.7 0.67
Normal 0.86 0.8 0.74 0.69 0.64 0.6
Dirty 0.83 0.75 0.68 0.62 0.57 0.53
 Closed Distribution Very Clean 0.94 0.91 0.89 0.87 0.86 0.85
Clean 0.88 0.83 0.79 0.75 0.72 0.7
Normal 0.82 0.77 0.73 0.69 0.65 0.62
Dirty 0.77 0.71 0.66 0.61 0.57 0.53
Indirect-Distribution Very Clean 0.93 0.88 0.85 0.82 0.79 0.77
Clean 0.86 0.77 0.7 0.64 0.59 0.55
Normal 0.81 0.66 0.55 0.48 0.43 0.4
Dirty 0.74 0.57 0.45 0.38 0.33 0.3
  • Dirt on acclimation on Lamp Surface can be minimized by proper sealing of lamp compartment against entry of moisture and dust. This can be achieved by selecting proper IP rating of fixture.

(D) Lamp Survival Factor (LSF): (Lamp Failure Rate)

  • The % of lamps still operating in an installation after a specified number of hour’s operation.
  • LSF Lamp Survival Factor takes account of the effect of the failure of light sources during the maintenance period. (reduced light output due to lamps failing)
  • It is determined by the failure rate at the end of the estimated period of use of light sources.
  • The lamp survival factor depends on the service lifetime of a lamp.
  • Some lamp lifetimes are reduced by frequent switching.
  • The lamp manufacturers provide tables indicating the lamp survival factor.
  • If a lamp is not working any more, the decision for immediate replacement or group replacement needs to be taken. If the lamp is replaced immediately (mostly in areas where the luminaire is easily reachable) the LSF can be 1.
  • LSF 1 is saying that there will be no loss of light because of lamp failure.
  • On the other hand, the decision could be to replace lamps in special terms or GroupWise. This could be the case in huge halls, where machines need to be stopped to reach the luminaires. The stopping of the machines is connected to less production rates of the factory, so they won’t change each single lamp. 
Lamp Survival Factors (LSF)
Lamp Type Operating Hours
4000 Hr 6000 Hr 8000 Hr 10000 Hr 12000 Hr
High Pressure Sodium 0.98 0.96 0.94 0.92 0.89
Metal Halide 0.98 0.97 0.94 0.92 0.88
High Pressure Mercury 0.93 0.91 0.87 0.82 0.76
Low Pressure Sodium 0.92 0.86 0.8 0.74 0.62
Tubular Fluorescent 0.99 0.99 0.99 0.98 0.96
Compact Fluorescent 0.98 0.94 0.9 0.78 0.5


  • Calculate Utilization Factor and Maintenance Factor for Office having following Details.
  • Length of Room is 10meter and width of Room is 20Meter.
  • Lighting Fixture mounting Height is 3 Meter.
  • Room Wall color is ivory White. Ceiling Color is ivory White and Flooring Color is Dark Gray
  • Office Working hours: 5 days a week, 16h each day, 50 working weeks a year (4000h/a)
  • Type of Lamp : Compact Fluorescent
  • Type of Fixtures : Direct Luminaires
  • Room Surface: Cleaned
  • Room Cleaning Frequency: 1 time in Annum.
  • Total Lamp Working Hour : 16Hour/Day , 5Day/Week, 50Week/Year (4000H/Annum)


Utilization Factor

  • Room Refection from above Table are
  • Wall=0.5. Ceiling=0.7and Flooring=0.2
  • Fixture Mounting Height is 3 Meter.
  • Room Index = L x W / ((L + W)x Hm)
  • Room Index=(10×20) / ((10×20)x3) =2
  • From Above Table Utilization Factor is 0.6

Maintenance Factor

  • Room Surface Maintenance Factor (RSMF):
  • Room is Clean and Frequency of Room Cleaning is 1time/Annum.
  • From Above Table RSMF if 0.95
  • Lamp Luminaire Maintenance Factor (LLMF):
  • Type of Lamp is Compact Fluorescent and Lamp Working hour is 4000Hr/Annum.
  • From Above Table LLMF if 0.91
  • Luminaire Maintenance Factors (LMF):
  • Lamp distribution is direct and Frequency of Room Cleaning is 1time/Annum..
  • From Above Table LMF if 0.9
  • Lamp Survival Factor (LSF):
  • Type of Lamp is Compact Fluorescent and Lamp Working hour is 4000Hr/Annum.
  • From Above Table LSF if 0.98.
  • Maintenance Factor = RSMF x LMF x LLMF x LSF
  • Maintenance Factor = 0.95×0.9×0.91×0.98
  • Maintenance Factor =0.76



Calculate Transformer Regulation & Losses (As per Transformer Name Plate)

Calculate Transformer Regulation and Losses for following Transformer Name Plate Details

  • KVA rating of Transformer(P)=16000VA
  • Primary voltage(Vp)=11000V
  • Secondary voltage(Vs)=433V
  • No load losses(W0)=72Watt
  • No load current(I0)=0.59Amp
  • Full load losses(W)=394Watt
  • Impedance voltage(Vi)=480Volt
  • LV resistance(Rs) =219.16 miliΩ
  • HV resistance(Rp) =215.33 Ω
  • Amb temperature(c)=30 Deg C
  • Total Connected Load on Transformer(Pl)=10000VA


  • % Loading of Transformer=Pl/P
  • % Loading of Transformer=10000/16000 = 63%

I2R Calculation:

  • HV Full load current (Ip) =P/Vpx1.732
  • HV Full load current (Ip) =16000/11000×1.732=0.84 Amp
  • LV Full load current (Is)=P/Vsx1.732
  • LV Full load current (Is)==16000/433×1.732=21.33 Amp
  • HV Side I2R losses= IpxIpxRp
  • HV Side I2R losses= 0.84×0.84×215.33=227.8 Watt—–(A)
  • LV Side I2R losses= IsxIsxRs
  • LV Side I2R losses==21.33×21.33×219.16=149.63 Watt—(B)
  • Total I² R losses @ Amb temp(Ir)=A+B
  • Total I² R losses @ Amb temp(Ir)=227.8+149.63=377.43 Watt
  • Total Stray losses @ Amb temp (Ws) =Full Load Losses-I2R Losses
  • Total Stray losses @ Amb temp (Ws) =394-377.43=16.57 Watt
  • I² R losses @75° c temp =Irx310/235xc =149.63×310/235×30 =441.52Watt
  • Stray loses @ 75° c temp  =(Wsx(235+c))/310
  • Stray loses @ 75° c temp  =(16.57x(235+30))/310=14.16 Watt
  • Total Full load losses at @75° c=441.52+14.16=455.69 Watt
  • Total Impedance at ambient temp (Ax)=Vix1.732/Ip
  • Total Impedance at ambient temp(Ax)=480×1.732/0.84=989.94Ω
  • Total Resistance at amb temp (Ar)=Ir/IpxIp
  • Total Resistance at amb temp (Ar)=377.43/0.84×0.84=535.15Ω
  • Total Reactance (X)=√AxxAx+ArxAr
  • Total Reactance (X)=√989.98×989.94+535.15×535.15=832.82Ω
  • Resistance at@ 75° c (R)= (310xAr)/(235+c)=310×535.15/235+30 = 626.03Ω
  • Impedance at 75° c (X1)=√2X+2R=√2×626.03+2×832.82 = 1041.88Ω
  • Percentage Impedance = (X1x0.5774xIpx100)/Vp
  • Percentage Impedance = (1041.88×0.5774×0.84×100)/11000=4.59%
  • Percentage Resistance (R%)  =(Rx0.5774xIpx100)/Vp
  • Percentage Resistance(R%) =(626.03×0.5774×0.84×100)/11000=2.76%
  • Percentage Reactance(X%) = (Xx0.5774xIpx100)/Vp
  • Percentage Reactance(X%) = (832.82 x0.5774×0.84×100)/11000=3.67%


  • Regulation at Unity P.F =2.76
  • Regulation at Unity at 0.8 P.F =((R% x cosØ)+(X% x SinØ))+(0.005x((R% x SinØ)+(X% x CosØ)))
  • Regulation at Unity at 0.8 P.F =((2.76 x 0.8)+(3.67 x 0.6))+(0.005x((2.76 x0.6)+(3.67 x 0.8)))=4.43


  • Total I² R losses @ Amb. temp(Ir)= 377.43Watt
  • Total Stray losses @ Amb. temp (Ws) =16.57 Watt
  • Regulation at Unity P.F =2.76
  • Regulation at Unity at 0.8 P.F =4.43



Type of Lighting Bulbs (Shapes and Sizes) Part-5

(5) BT (Blown or Bulbous Tube) Type HID Bulbs (Code: ET)

  • BT means “Blown or Bulbous Tube”.
  • (BT )The blown tube light bulb is a HID Tube Type (T) light bulb that has had the glass blown in the middle so that it appears to have a bubble in the middle of the tube.
  • BT halogen light bulbs can be used to replace incandescent light bulbs.
  • Nomenclature: BT28, BT37.
  • Numbers in each code refer to the bulb’s diameter in one-eighths of an inch.
  • BTR20 bulb: 20/8 = 2-1/2″ diameter
  • Lighting direction: illuminates its light in one direction.
  • Bulb Technology: High Intension Discharge Lamps, Metal Halide Lamp, Sodium Discharge, Mercury Vapor Lamp and LED.

  • Applications:
  • These are used in sports arenas, car dealerships, canopy lighting, and industrial applications.

Lighting Bulb according to Applications:

(1) Flood Light (Code: F)

  • A flood light is a large, powerful fixture which has a wide beam spread.
  • It is a high-intensity to illuminate a large area. Most often used outside.
  • Floodlights are mostly used to illuminate outdoor playing fields and sports events. It can also be used indoors for lighting stages to create an artificial daytime setting.
  • When choosing a floodlight, some points to be considering like Fixture types, Bulb Type, Type of mounting wall-mounted, ground-mounted and post top.
  • Nomenclature: F40, F20.
  • Numbers in each code refer to the bulb’s diameter in one-eighths of an inch.
  • Bulb Technology: Fluorescent , Metal halide lamps, LED, Halogen

  • Application:
  • Advertisement board and Subway
  • Airport and Architecture lighting
  • Football and tennis field
  • Tunnels and parks
  • Clubs, Bars, Hotels and Art galleries
  • Villa and parking lot

(2) Panel Lighting:

  • LED panel lights are very thin either surface or recessed mounted ceiling light.
  • Panel lights are square, Round or rectangular.
  • LED panel lights are high-grade indoor lighting lamps.
  • They are made of aluminum alloy by anodic oxidation.
  • It has simple design and appearance with adorable illumination effects.
  • It comes with different powers like 12W, 18W, 21W, 36W, 48W, 72W, and 85W.
  • It used for home application and easy to install by recessed application with clamping springs.
  • Recess mounted Slim Circular type LED color changing panel light in white finish with anti-glare diffuser and separate energy efficient electronic driver.
  • Nomenclature: Panel
  • Lighting direction: illuminates its light in one direction.
  • Bulb Technology: LED, CFL.

  • Applications:
  • Low-profile 6″ Round LED Panel Light for kitchen lighting, living room lighting, office lighting, basement lighting, museum lighting, hospital lighting.

(3) Down Light

  • Downlights in help to create a feeling of more space, clean lines, and a clutter-free environment.
  • A downlight is mostly hidden in or above the ceiling. The only visible part of the light fitting is the decorative rim, and the light bulb in the middle. Everything else is held in place in the ceiling by spring clips that stop the whole thing giving in to gravity and falling out.
  • Nomenclature: Down Light.
  • Lighting direction: illuminates its light in one direction.
  • Bulb Technology: LED, CFL.

  • Applications:
  • Downlight especially in kitchens and bathrooms have become very popular, as they provide a modern appearance to the room. More recently the trend has spread to every other room. Lounges, bedrooms and hallways all look great when fitted with recessed downlight.

Difference Between Panel Light and Down Light.

  • There is confusion between Panel light and Down Lights. Both Lights are either Round or Square shaped, so we cannot easily difference between them.
  • There are some differences between LED panel light and downlight in following points.
  • Structure
  • Both have a diffuser to spread out light. The panel light has a light guide plate (LGP) which guides light across the panel so that it is evenly spread. There is a reflector plate right at the back of the LED guide plate (LGP) which reflect lighting source.
  • The downlight does not have this type of arrangement.
  • Lighting
  • Inside LED panel light, the LED is fitted around (In a circular frame). The LGP and the diffuser gather the light and spread it creating an evenly soft lighting.
  • The downlight lighting on the other hand have a LED in the middle. Consequently, the light produced is brighter than in the round panel light.
  • Size of Heat Sink:
  • Typically, the downlight has a thicker heat sink than the panel light.
  • Fixture Thickness:
  • LED panel light is super thin, looks simple but stylish.
  • Fixture Size Vs Lumen:
  • To spread light uniformly all Panel light are made with high dimension fixture. As you increase output watt you will have to choose bigger and bigger.
  • Power Saving:
  • Panel lights are less power saver compared to Down Light.
  • Panel lights have efficiency of only 60-80 Lm/watt compared to down light which has efficiency of 100-120 Lm/watt.
  • Applications:
  • If you are looking for bright LED lighting, your best choice will be the downlight. However, if you are angling for a softer and relatively polished feel to the room, then go for the round panel.

(4) Strip Light

  • Strip lights are available in both tape and rope configurations.
  • Nomenclature: Strip
  • Lighting direction: illuminates its light in one direction.
  • Bulb Technology: LED

  • Applications:
  • Under-counter Lights, cove Lights, Display lighting and Exterior Lighting


Bulb Shapes and Applications

Code Bulb Shape Designations Type of Bulbs Applications
A Arbitrary Incandescent ,CFL ,LED, Metal Halide, High Pressure Sodium ,Mercury vapor, In household light.

Table lamps.

Wall Light, Ceiling lights.

AR Arbitrary with Reflector Incandescent ,CFL ,LED, Metal Halide, High Pressure Sodium ,Mercury vapor, In household light.

Table lamps.

Wall Light, Ceiling lights.

B Bulged Incandescent ,CFL ,HID,LED In various light fixtures,

Decorative Lights.

BT Blown Tubular Incandescent ,CFL ,HID,LED Less in general used,

In various light fixtures.

Table Lamp.

BR Bulged Reflector Incandescent ,CFL ,HID,LED In Track lighting (spot lights)

In recessed lighting.

MR Mirror Reflector LED In Track lighting
C Candle Incandescent ,CFL ,HID,LED Widely used in ceiling and table chandeliers and decorative light fixtures.

In small appliances and indicator lamps

They have a smaller base.

CA Candle Angular Incandescent ,CFL ,HID,LED Like Candle bulbs, used in chandeliers and similar light fixtures.

They also often have a smaller base.

CW Candle Twisted Incandescent ,CFL ,HID,LED These are used in chandeliers and have smaller bases.
CP Crystalline Pear Incandescent ,CFL ,HID,LED Used in various decorative light fixtures

in wall lights, ceiling lights and table lamps.

To create interesting reflective effects.

E Ellipsoidal Incandescent ,CFL ,HID,LED Widely used in various light fixtures.
ER Extended Reflector Incandescent ,CFL ,HID,LED in track lighting and other fixtures for spot lights.
F Flambeau Incandescent ,CFL ,HID,LED in chandeliers and similar decorative interior lighting fixtures.
G Globe Incandescent ,CFL ,HID,LED Widely used in ceiling and table lamps.

in Bathrooms.

In ornamental lighting and some floodlights

GA Decorator Incandescent ,CFL ,LED Used in ceiling lamps, table lamps and other decorative fixtures.
HX Hexagonal Candle Incandescent ,CFL ,LED Used in chandeliers and other decorative light fixtures to create beautiful reflective light effects.
P Pear Incandescent ,CFL ,LED Used in various light fixtures.

In standard for streetcar and locomotive headlights

PAR Parabolic Aluminum Reflector Incandescent ,CFL ,LED Widely used in track lighting and spot light fixtures.

used in floodlights

PC Ogive Incandescent ,CFL ,LED Used in decorative light fixtures.
PS Pear Straight Incandescent ,CFL ,LED Used in various light fixtures.
R Reflector Incandescent ,CFL ,LED Widely used in Recessed cans  and track lighting ,spot light fixtures.
S Straight Sided Incandescent ,CFL ,LED Used in various light fixtures.

lower wattage lamp as sign and decorative

ST Straight Tubular Incandescent ,CFL ,LED Used in various light fixtures.
T Tubular Incandescent ,CFL ,LED Used in various light fixtures according to functional rather than decorative purposes.

Showcase and appliance lighting =In closets/garages.

TA Tubular Angular Incandescent ,CFL ,LED Used in various light fixtures, often for decorative effect.





Type of Lighting Bulbs (Shapes and Sizes) Part-4

What is difference between R,BR,MR and PAR bulbs

(1) Difference between an R and BR Bulb

  • There is confusion between selecting R and BR type of Bulbs.
  • There is minor difference between R and BR type Bulb.
  • Both types of Bulbs have a reflector flood, and that is what the R stands for in the code.
  • The R is an old design for reflectors that are not as energy efficient as a BR reflector.
  • The BR was designed to replace the older R.
  • For same Light output and size in length and width, BR Bulb use less watts (due to the reflector in a BR is more directed) hence BR Bulb produce less heat and more efficient.
  • Both of these lamp types are interchangeable.
  • BR is an upgraded version of R 

(2) Difference between PAR and BR / MR Bulb:

  • The main difference between PAR and MR is according to its Size, variety, and heat transformation.
  • The primary difference between these bulbs is according to Beam Angle, internal construction and as per Reflector.
  • Different Type of Beam Angles.
  • BR (for bulged reflector) bulbs are lamps with “wide flood” beam angles, which means that they provide more than a 45 degree angle when lighting an area.
  • PAR (Parabolic Aluminized Reflector) bulbs are available in these angles:
  • Narrow spot (5 to 15 degrees)
  • Spot, (16 to 22 degrees)
  • Narrow flood,( 23 to 32 degrees)
  • Flood, (33 to 45 degrees(
  • Wide flood beam, over 45 degrees.

  • Different Type of Reflector and Application of Bulb.
  • The BR bulbs have a frosted/patterned coating of reflector (for broad beam angle ) allows to less concentrated light and provides better coverage thus eliminating shadows in the intended area hence BR Bulb produces less shadow than PAR bulbs.
  • BR Bulbs are commonly used indoors in household ceilings like in kitchens, family rooms, and stair lighting with high ceilings with recessed type.
  • The reflective surface of PAR does not allow light to spread much further than the angle of the beam spread hence PAR lamps deliver strong, narrow to wide, directional light , which is little harsher where the light starts and where it ends.
  • A PAR bulb is used in indoor/outdoor security lighting, theatre, performance sets, and spot-lighting signs and restaurant lighting applications as well.
  • Different Type of Construction and Heat dissipation.
  • BR bulbs are a common reflector lamp with a bulged reflector. They are incandescent, LED bulbs. The sides of the outer part of the blown glass bulb are coated with a reflecting material that directs light. The light transmission pattern can be clear, frosted, or even patterned.
  • PAR bulbs are incandescent, tungsten-halogen, metal halide, LED Bulbs. They have a hard glass cover which is hermetically (airtight) sealed to the reflecting surface. Inside there is a lenses that controls beam spread and cannot be altered in position in relation to the filament. There are flood bulbs and spot bulbs. Flood bulbs diffuse or scatter light, while spots focus all light in one direction.
  • MR type bulbs have dichotic glass reflectors while PAR bulbs have aluminized glass reflectors which direct the heat generated by the bulb to the front of the bulb. Due of this, PAR bulbs are not suitable for ceiling installations of 8 feet or lower.
  • PAR bulbs also produce more directional yet duller lighting and have a standard, medium screw-in type of base and work in medium sized E26 sockets.
  • MR on the other hand, generates heat to the rear of the bulb and produces a lot more light for the wattage because of the multi-faceted reflector (MR).

Lighting Bulb according to HID Technology:

(1) E (Elliptical) Type HID Bulbs (Code: E)

  • E means HID Type light bulb that has a shape of “Elliptical”.
  • E Type Halogen light bulbs can be used to replace incandescent light bulbs. High intensity discharge light bulbs.
  • Nomenclature:
  • Numbers in each code refer to the bulb’s diameter in one-eighths of an inch.
  • E20 bulb: 20/8 = 2-1/2″ diameter
  • Lighting direction: illuminates its light in one direction.
  • Bulb Technology: incandescent, CFL, High Intension Discharge Lamps, Metal Halide Lamp, Sodium Discharge, Mercury Vapor Lamp and LED.

(2) ED (Elliptical Dimple) Type HID Bulbs (Code: ED)

  • ED means “Elliptical Dimple”.
  • ED light bulbs have an elliptical shape to house the arc tube of a high intensity discharge light bulb.
  • They are not as efficient as their alternatives, but their use may be dictated by color rendering requirements. The lamps require only ballast for additional control.
  • Inside surfaces coated with europium-activated phosphor which converts the UV elements in ’warm’ light to produce a cool white light. They are an acceptable alternative to fluorescent lighting
    Nomenclature: ED17.
  • Numbers in each code refer to the bulb’s diameter in one-eighths of an inch.
  • EDR20 bulb: 20/8 = 2-1/2″ diameter
  • Lighting direction: illuminates its light in one direction.
  • Bulb Technology: High Intension Discharge Lamps, Metal Halide Lamp, Sodium Discharge, Mercury Vapor Lamp and LED.
  • Applications:

  • ED light bulbs are used in sports arenas, high bay industrial lighting, parking lots and garages and car dealerships.
  • These lamps are used in some industrial, warehousing applications as a floodlight and other suitable light fittings with appropriate ballast gear.
  • Metal Halide HID light bulb produces high light output
  • Ideal for various commercial and industrial applications where color rendering is important
  • Retail areas
  • Area lighting
  • Accent lighting
  • Sports lighting
  • Security lighting
  • Parking garages

(3) ER (Elliptical Reflector) Type HID Bulbs (Code: ER)

  • ER means “Elliptical Reflector”.
  • In ER bulb, the elliptical reflector increases the overall lumen output by redirecting side light of Bulb (Which is normally lost) to the redirect it to the forward Side of Bulb.
  • Elliptical (ellipsoidal) reflector light bulbs are uniquely designed to project light further than other reflector bulbs. They are a great option for use in deep recessed can lights as they lose less light in baffles than standard BR or R type bulbs. 
  • ER halogen light bulbs can be used to replace incandescent light bulbs. High intensity discharge light bulbs.
  • An incandescent lamp with a built-in elliptically-shaped reflecting surface. This shape produces a focal point directly in front of the lamp which reduces the light absorption in some types of luminaires. It is particularly effective at increasing the efficacy of baffled down lights.
  • Nomenclature: ER28, ER37.
  • Numbers in each code refer to the bulb’s diameter in one-eighths of an inch.
  • ER20 bulb: 20/8 = 2-1/2″ diameter
  • ER30 bulb: 30/8 = 3-3/4″ diameter
  • ER36 bulb: 36/8 = 4-1/2″ diameter
  • Lighting direction: illuminates its light in one direction.
  • Bulb Technology: incandescent, CFL, High Intension Discharge Lamps, Metal Halide Lamp, Sodium Discharge, Mercury Vapor Lamp and LED.

  • Applications:
  • The most common size is ER30. These light bulbs are used for down lighting in recessed cans for residential, hotel, and office applications.
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