How to Design efficient Street lighting-(Part-2)

(2) Proper Placement of Pole:

1

(A) 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

(B) 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.

(C) 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.

(D) 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.
  • 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.
  • 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.

(E) 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°

(F) 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.

 (G) 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.

 (H) 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
Rural
Highway
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 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/
0.33
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
/0.4
HP SV 150W
Pedestrian Pathway Single Carriage Single Sided 3m-6m 7.5 20-25 0.6 <0.5 meter  10° 20 lux
/0.4
HP SV 150W

 

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

 

About Jignesh.Parmar
Jignesh Parmar has completed M.Tech (Power System Control), B.E(Electrical). He is member of Institution of Engineers (MIE) and CEng,India. Membership No:M-1473586.He has more than 16 years experience in Transmission -Distribution-Electrical Energy theft detection-Electrical Maintenance-Electrical Projects (Planning-Designing-Technical Review-coordination -Execution). He is Presently associate with one of the leading business group as a Deputy Manager at Ahmedabad,India. He has published numbers of Technical Articles in “Electrical Mirror”, “Electrical India”, “Lighting India”,”Smart Energy”, “Industrial Electrix”(Australian Power Publications) Magazines. He is Freelancer Programmer of Advance Excel and design useful Excel base Electrical Programs as per IS, NEC, IEC,IEEE codes. He is Technical Blogger and Familiar with English, Hindi, Gujarati, French languages. He wants to Share his experience & Knowledge and help technical enthusiasts to find suitable solutions and updating themselves on various Engineering Topics.

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