Street Lighting Design

The main consideration for street lighting is safety and security of users. The obstacles present across and along the roadway should be clearly visible for safe and secure movement of passengers. To ensure that streets should be properly lit as per guidelines.

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Key measuring Parameters for Road Lighting

  1. Luminance -Road lighting level is measured as average luminance or the amount of brightness of road surface.
  2. Uo -Overall uniformity of the road across each lane, which is the ratio of minimum to average luminance.
  3. Ul -Longitudinal uniformity of the lane, which is the ratio of minimum to maximum luminance along the centerline of each lane.
  4. TH-Threshold increment – Measures the disability glare due to which the percentage increase, in contrast, is required between an object and its background.
  5. SR-Surround Ratio- is the measure of the visibility of the surrounding area of the road in comparison to the road.

Hence the key factors to be considered for road lighting design are:

  1. Luminance level to be within the standards for that particular roadway
  2. The uniformity level within the limits
  3. Threshold increment and surround ratio within the regulations.

The most prevalent standard for Road Lighting in Europe and middle east is CIE 115 and CIE140. The American standard for roadway lighting is ANSI-IESNA RP-8-00. These are the most prevalent standards for roadway lighting all over the world.

Road Lighting is significant in visually complex area where there are various types of road users like motorists, cyclists, pedestrians etc.

Road lighting should be providing safety, security, improve energy efficiency, and protect consumers, workers and the environment. Road lighting standards are developed to take at most care of all the above.

According to CIE115 and CIE140 the road lighting classes are divided based on the following:

  • M classes – For motorized traffic on roads with medium to high driving speed.
  • C classes – For motorized traffic, but applicable on conflict areas
  • P classes – are intended for pedestrians and cyclists
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The lighting level required for roadway is determined based on the following:

  1. Speed of traffic and volume of traffic, 
  2. The type of traffic, motorized or pedestrian
  3. Presence of traffic conflict areas
  4. Separation of Carriageways
  5. Parked Vehicles
  6. Ambient luminance
  7. Navigation, Visual guidance, and Traffic control

M class of lighting varies from M1 to M6 which are selected based on the weighting values for various parameters (listed in clause 1 to 7 above) added to find the sum of the weighting values (VWS) The number of the lighting class M is then calculated as: Number of lighting class
M = 6 – VWS

Ref: Table 1 & 2 from CIE115:2010

Table 1: Parameters for the selection of M lighting class

Parameter Options Weighting Value Vw Vw Selected
Speed Very High 1
High 0.5
Moderate 0
Traffic Volume Very High 1
High 0.5
Moderate 0
Low -0.5
Very Low -1
Traffic Composition Mixed with a high percentage of non-motorized 2
Mixed 1
Motorized Only 0
Separation of Carriageways No 1
Yes 0
Intersection Density High 1
Moderate 0
Parked Vehicles Present 0.5
Not Present 0
Ambient Luminance High 1
Moderate 0
Low -1
Visual Guidance / Traffic Control Poor 0.5
Moderate Or Good 0
Sum Of Weighting Values VWS
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Table 2: Lighting classes for motorized traffic, based on road surface luminance

Lighting Class Road Surface Threshold Increment Surround Ratio
Dry Wet
Lav in cd.m-2 Uo Ul Uo fTi in % Rs
M1 2,0 0,40 0,70 0,15 10 0,5
M2 1,5 0,40 0,70 0,15 10 0,5
M3 1,0 0,40 0,60 0,15 15 0,5
M4 0,75 0,40 0,60 0,15 15 0,5
M5 0,50 0,35 0,40 0,15 15 0,5
M6 0,30 0,35 0,40 0,15 20 0,5

Conflict Area Lighting

For conflict areas, illuminance of the roadway is calculated and other parameter which is measured is overall uniformity.

Ref: Table 3 & 4 from CIE115:2010

Table 3: Parameters for the selection of C lighting class

Parameter Options Weighting Value Vw Vw Selected
Speed Very High 3
High 2
Moderate 1
Low 0
Traffic Volume Very High 1
High 0.5
Moderate 0
Low -0.5
Very Low -1
Traffic Composition Mixed with a high percentage of non-motorized 2
Mixed 1
Motorized Only 0
Separation of Carriageways No 1
Yes 0
Ambient Luminance High 1
Moderate 0
Low -1
Visual Guidance / Traffic Control Poor 0.5
Moderate Or Good 0
Sum Of Weighting Values VWS

Number of lighting class C = 6 – VWS

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Table 4: Lighting classes for conflict areas

Lighting Class Average Illuminance

over the whole of

used Surface E in lx

 Uniformity of

Illuminance

Uo (E)

 Threshold Increment

fTi in %  (1)
High & Moderate

speed

 Low and Very

Low Speed
C0 50 0,40 10 15
C1 30 0,40 10 15
C2 20 0,40 10 15
C3 15 0,40 15 20
C4 10 0,40 15 20
C5 7,5 0,40 15 25

1) Applicable where visual tasks usually considered for the lighting of roads for motorized traffic (M classes) are of importance

C lighting class selection or weightage calculation method is based on same parameters as used for M class.

As recommended by standards, the lighting class for conflict areas should be one step higher than the adjacent roadway to enable visual guidance.

Pedestrian and Cycle Path Lighting

Ref: Table 5 & 6 from CIE115:2010

Table 6: Parameters for the selection of P lighting class

Parameter Options Weighting Value Vw Vw Selected
Speed Low 1
Very Low (walking Speed) 0
Traffic Volume Very High 1
High 0.5
Moderate 0
Low -0.5
Very Low -1
Traffic Composition Pedestrians, cyclists, and motorized traffic 2
Pedestrians, and motorized traffic 1
Pedestrians, and Cyclists Only 1
Pedestrians Only 0
Cyclists only 0
Parked Vehicles Present 0.5
Not Present 0
Ambient Luminance High 1
Moderate 0
Low -1
Facial Recognition Necessary Additional Requirements
No Additional Requirements
Not Necessary
Sum Of Weighting Values VWS

Number of lighting class C = 6 – VWS

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Table 6: Lighting classes for pedestrian and low speed traffic areas

Lighting Class Average Horizontal

Illuminance

Eh,av in lx

 Minimum Horizontal

Illuminance

Eh,min in lx

 Additional Requirement

if facial recognition is necessary
Minimum Vertical

Illuminance

Ev,min in  lx

 Minimum Semi

Cylindrical Illuminance

Esc,min in lx
P1 15 3,0 5,0 3,0
P2 10 2,0 3,0 2,0
P3 7,5 1,5 2,5 1,5
P4 5,0 1,0 1,5 1,0
P5 3,0 0,6 1,0 0,6
P6 2,0 0,4 0,6 0,4

Note:

  1. To provide for uniformity the actual value of the maintained average illuminance may not exceed 1.5 times the value indicated for the class.
  2. A high colour rendering contributes to better facial recognition.

Facial recognition is an important factor to be considered for the P class lighting levels.

To cut short road lighting should be visually appealing and comfortable and should ensure safety and security of users.

Sample Road Lighting Design – Dialux Render

Sample Road Lighting Design Dialux Render
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