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 A1Important routes with rapid and dense traffic where safety, traffic speed, and driving comfort are the main considerations
Class A2Main Roads with considerable volume of mixed traffic, such as main city streets, arterial roads and thoroughfares.
Class B1Secondary roads with considerable traffic such as main local traffic routes, shopping streets
Class B2Secondary roads, with light traffic
Class CLighting for residential and unclassified roads not included in previous groups
Class DLighting for bridges and flyovers
Class ELighting for town and city centers
Class FLighting for roads with special requirement such as roads near air fields, railways and docks



AHeavy and high speed motorized trafficRoad with fixed separators, No crossings for very long distanceNational highways or state highways or called interstate highways, express ways or motor ways
BSlightly lower density and lower speed traffic termedRoad which is made for vehicular traffic with adjoining streets for slow traffic and pedestrians as we find in metrosTrunk road or major road in a city
CHeavy and moderate speed trafficImportant urban roads or rural roads. they do not interfere with the local traffic within the townRing roads
DSlow traffic, pedestriansLinking to shopping areas and invariably the pedestrians, approach roadShopping street, trunk road
ELimited 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 SpeedPole Set Back
50 Km/Hr0.8 Meter
80 Km/Hr1 Meter
100 Km/Hr1.5 Meter
120 Km/Hr1.5 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 HeightArm LengthArm Tile Angle
6 Meter0.5 Meter5°,10°,15°
8 Meter1 Meter5°,10°,15°
10 Meter1.5 Meter5°,10°,15°
>=12 Meter2 Meter5°,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 HeightApplication
< 6 MeterMajority of side streets or alleys, Public gardens and parking Area to make people feel safe
8 MeterUrban traffic route , the multiplicity of road junctions
10 MeterUrban traffic routes
12 MeterHeavily used routes
18 MeterHigh 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

RoadRoad Width (Meter)Pole ArrangementLamp (Watts)Pole to Pole Spacing (Meters)Mounting Height, (Meters)Arm Length, (Meters)
Expressway10Twin Central25025 To 35121.5
1525020 To 35123.0
20Opposite25020 To 45121.5
2525020 To 40121.5
3025020 To 30121.5
3625020 To 25121.5
4025020 To 22121.5
Major10One-side25010 To 40101.5
1525010 To 45123.0
10Twin Central15020 To 37101.5
1525020 To 43123.0
20Opposite15020 To 40103.0
2525020 To 45101.5
3025020 To 45101.5
3625020 To 45123.0
4025020 To 4523.0
Collector10One-side15010 To 40101.5
1525010 To 50123.0
10Twin Central15020 To 40101.5
1515020 To 37123.0
20Opposite15020 To 47101.5
2525020 To 48101.5
8One-side15010 To 3881.5
1015010 To 3783.0
1515015 To 38103.0
10Twin Central15020 To 45103.0
1515020 To 39123.0
Minor4One-side7010 To 4081.5
67010 To 4081.5
87010 To 4081.5
107010 To 3981.5
10Twin Central7020 To 3581.5
15Staggered7010 To 2081.5
15Opposite7020 To 4081.5


Illumination Level

Classification Average Illumination (lux)Ratio Minimum to average illumination
Class A1300.4
Class A2150.4
Class B180.3
Class B240.3


Relationship between Mounting Height and Spacing of Fixtures

Pole ArrangementCut-off typeSemi cutoff type
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 HeightLampPole to Pole DistanceMax. Illumination (Lux)Average (Lux)
4 Meter15 watt12 to 18 Meter2518
5 Meter18 watt14 to 20 Meter3018
6 Meter30 watt18 to 24 Meter3220
7 Meter50 watt21 to 28 Meter3220
8 Meter100 watt24 to 32 Meter4022
9 Meter110 watt27 to 35 Meter3420
10 Meter140 watt30 to 40 Meter3522
12 Meter180 watt30 to 40 Meter3323
14 Meter200 watt30 to 40 Meter3021


Lux Vs Mounting Height

Fixtures (Lux)Mounting Height
3000 to 10000 Lux6 to 7 Meter
10000 to 20000 Lux7 to  9 Meter
More than 20000 LuxMore than 9 Meter


Road – Pole Details

RoadRoad TypeType of Pole positionsIndividual 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 AngleLighting SpecificationsLamp (Watt)
A1Dual CarriageCentral Verge101.212400.61 meter 10°35 lux
/0.4/ 0.33
HP SV 400W
A1Dual CarriageCentral Verge111.212400.61 meter 10°35 lux
/0.4/ 0.33
HP SV 400W
A1Dual CarriageCentral Verge121.212400.61 meter 10°35 lux
/0.4/ 0.33
HP SV 400W
A1Dual CarriageCentral Verge141.212400.61 meter 10°35 lux
/0.4/ 0.33
HP SV 400W
A1Dual CarriageCentral Verge161.212400.61 meter 10°35 lux
/0.4/ 0.33
HP SV 400W
A1Single CarriageOpposite12012350.61 meter 10°35 lux
/0.4/ 0.33
HP SV 250W
A1Single CarriageOpposite14.5012350.61 meter 10°35 lux
/0.4/ 0.33
HP SV 250W
A1Single CarriageOpposite16012400.6Around one meter 10°35 lux
/0.4/ 0.33
HP SV 400W
A1Single CarriageOpposite18012400.61 meter 10°35 lux
/0.4/ 0.33
HP SV 400W
A1Single CarriageOpposite21012400.61 meter 10°35 lux
/0.4/ 0.33
HP SV 400W
Single CarriageOpposite25012400.61 meter 10°35 lux
/0.4/ 0.33
HP SV 400W
A1Single CarriageOpposite31012400.61 meter 10°35 lux/ 0.4/
HP SV 400W
A2Single CarriageSingle Sided1011300.6< 1.0 meter 10°25 lux
/0.4/ 0.33
HP SV 250W
A2Single CarriageSingle Sided911300.6< 0.5 meter 10°25 lux
/0.4/ 0.33
HP SV 250W
A2Single CarriageSingle Sided711300.6< 0.5 meter 10°25 lux
/0.4/ 0.33
HP SV 250W
A2Single CarriageSingle Sided711300.6< 0.5 meter 10°25lux
/0.4/ 0.33
HP SV 250W
A3Single CarriageSingle Sided78200.6< 0.5 meter 10°20lux
HP SV 150W
Pedestrian PathwaySingle CarriageSingle Sided3m-6m7.520-250.6<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)


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

Type of RoadRoad CharacteristicsRoad Width (Meter)Average Level of Illumination on Road Surface in LuxRatio of Minimum/Average IlluminationRatio of Minimum/Max IlluminationType of Luminaire PreferredLuminas Mounting Height
A-1Important traffic routes carrying fast traffic>10.5,12,14,16,18,20,30300.433Cutoff9 To 10 Meter
A-2Main roads carrying mixed traffic like city main roads/streets, arterial roads, throughways> 7 m up to 10 m150.433Cutoff9 To 10 Meter
B-1Secondary roads with considerable traffic like local traffic routes, shopping streets< 7m Colony Roads80.320Cutoff or semi-cutoff7.5 To 9 Meter
B-2Secondary roads with light traffic4m,5m, 6m40.320Cutoff or semi-cutoff7.5 To 9 Met