Road Lighting

2

• An object has to be seen against its background: the road surface

Visibility of objects

3

luminance illuminance

- contrast

Object is seen against its background

Road Lighting principle: Negative contrast

4

Visibility: ability of motorist to detect objects

Revealing power

Revealing power is usedin road lighting as a reference to evaluate visibility of objects

5

• An object has to be seen against its background: the road surface

• The visibility of the object depends on:– Object luminance (cd/m2)

Visibility of objects

6

• An object has to be seen against its background: the road surface

• The visibility of the object depends on:– Object luminance (cd/m2)– Road luminance (cd/m2)

Visibility of objects

7

luminanceluminance

illuminanceilluminance

Road luminance

8

Luminance ( L ) is the brightness of the road surface as seen by the driver / observer

Lav Expressed in: “cd / m2”

Design parameters

9

Road Luminance (Lav)

Design parameters

10

w

s

60m

Road luminance: Observer position

11

Road luminance: Impact of luminance level

0.750.50

12

Reflection coefficient as per Asphalt CIE R3 : Q0 = 0.07

• Lay out• Photometry• Light source

Road luminance: Key influencing factors

13

distance60 meter

distance

max.100m

height of observer 1.50m

2 luminaires in a same row are enclosed

Observer in the center

of each lane

LUMINANCE : Field of calculation

14

In the longitudinal direction : D = S / ND : spacing between points in the longitudinal direction, in metres

S : spacing between luminaires in the same row, in metres

N : number of calculation points in the longitudinal direction with the following values:

for S ≤ 30 m, N = 10;

for S > 30 m, the smallest integer giving D ≤ 3 m The first transverse row of calculation points is spaced at a distance D/2 beyond the first luminaire (remote from the observer).

Spacing of the points in a driving lane :

In the transverse direction : d = WL / 3d : spacing between points in the tranverse direction, in metres

WL : width of the lane, in metres

The outermost calculation points are spaced d/2 from the edges of the lane.

LUMINANCE: Position of calculation points

15

LUMINANCE: Position of observer

• Observer is located at the centre of each lane• Observer´s eye is 1,5 m above the road level

Operative value of average luminance is the lowestcalculated

16

• An object has to be seen against its background: the road surface

• The visibility of the object depends on:– Object luminance (cd/m2)– Road luminance (cd/m2)– Luminance uniformity

Visibility of objects

17

Uniformity: Uo , U1Shows how the light is distributed on the road

Design parameters

18

Overall uniformity is the ratio of the minimum to the average road luminance

A good overall uniformity ensuresthat all spots on the road are sufficiently visible

Overall uniformity: Definition

19

It is calculated for each observer, the lowest value is considered :Uo = Lmin/Lave

Lmin is the lowest luminance occuring at any grid point in the field of calculation

.Lmin

Lave

LUMINANCE: Overall uniformity

20

RP

0

25

5

0

7

5

10

0%

0.1 0.2 0.5 1 2 5 10 cd/m2

Laverage

U0=0.4

U0 =0.2

Revealing power: Impact of overall uniformity

Uo= 0.4

Uo= 0.2

21

• Mounting height ( h )• Spread

Overall uniformity: Key influencing factors

22

Longitudinal UniformityU1 = L-minimum

L-maximum

• Longitudinal uniformity is the lowest ratio of the minimum to the maximum road luminance in the middle of each lane

• A good longitudinal uniformity ensures comfortable driving conditions without the so-called ‘Zebra’ effect

Longitudinal uniformity: Definition

23

Calculated for each observer ; the lowest value is considered

The number of points in the longitudinal direction (N) and the spacing between them shall be the same as those used for the calculation of average luminance.

LUMINANCE: Uniformity lengthwise Ul

Lmin Lmax

24

Longitudinal uniformity: Key influencing factors

• Spacing ( S )• Throw

25

• An object has to be seen against its background: the road surface

• The visibility of the object depends on:– Object luminance (cd/m2)– Road luminance (cd/m2)– Luminance uniformity– Glare control

Visibility of objects

26

Sensation caused by Brightness of lanterns within the visual field which is brighter than the adaptation level of eye.

Design parameters: Glare

27

• Disability glare reduces the vision

• Discomfort glare creates unpleasant viewing conditions

• Threshold Increment (TI) represents both types of glareTI = the % increase in the luminance level required to make an object equally visible as in the absence of glare

Design parameters: Glare

28

RP

0

25

5

0

7

5

10

0%

0.1 0.2 0.5 1 2 5 10 cd/m2

Laverage

UO=0.4TI =7%

UO= 0.4TI =30%

Revealing power: Impact of TI

29

Threshold increment Assessment

%

> 20 Bad

10 Moderate

< 10 Good

Key influencing factors:• Lay out• Photometry

Threshold Increment

Operative value of TI shall be the highest value among observers.

30

Uniform, glare-free lighting :• Early anticipation when driving• Smoother traffic flow• Relaxed drivers• Increased road capacity

Uniformity and glare

31

SR is the average horizontal illuminance on the two longitudinal strips each adjacent to the two edges of the carriageway and lying off the carriagewayDividedby the average horizontal illuminance on the two longitudinal strips each adjacent to the edges of the carriageway but lying on the carriageway

Surround ratio: SR

Sufficient lighting in the surrounding of the road creates a proper adaptation of the eye

SR = Ekirb / Eroad ≥ 50%

32

: luminaires

EN 13201SR = (E1+E4) / (E2+E3)CIE 115SR(1) = E1/E2 SR(2) = E4/E3

The width of all four strips shall be the same, and equal to 5 m, or half the width ofthe carriageway.

Location of strips with width of strip equals 5 m :

For dual carriageways, both carriageways together are treated as a single carriageway unless they are separated by more than 10 m.

6

Surround ratio: SR

33

The width of all four strips shall be the same, and equal to 5 m, or half the width of the carriageway.

Location of strips with width of strip less than 5 m because width of carriageway is less than 10 m

: luminaires

EN 13201SR = (E1+E4) / (E2+E3)

Surround ratio: SR

34

In case of obstruction, the width of the unobstructed strip lying off the carriageway is applied on the 4 parts.

Location of strips with width of strip less than 5 m because of obstruction

: luminaires

: obstruction

EN 13201SR = (E1+E4) / (E2+E3)

Surround ratio: SR

35

Level Uniformity Glare

Visual performance

Lav Uo TI

Visual comfort

Lav Ul TI

↓• Lay out

( h, S )• Photometry• Light source

↓• Lay out

h → U0S → U1

• Photometry

↓• Lay out (h)• Photometry

Summary of lighting design parametersand related influencing factors

Norms and recommendationsas per CIE 115-1995

37

LightingPerformance

LuminanceUniformity

Glare

Total costs

Installation costMaintenance cost

Energy

Lighting norms

Road types

39

Provide main transport link between the towns

• Motorized traffic only • Separated carriage ways• No pedestrian crossing • High speed traffic

(80 km/hr to 150 km/hr)

• Number of lanes vary from 2 * 2 to 6

Motorways

40

Provide main transportlink within city

• Motorized traffic only • Sometimes, separated carriage way

provided for slow traffic orpedestrians

• Pedestrian crossings at road junctions• Traffic speed 50 km/hr to 80 km/hr

• Number of lanes vary from 2 * 2 to 6

Major roads

41

Provide transport link up to majorroad

• Mixed traffic and pedestrians• Low speed traffic• Number of lanes 2 • Many crossings, parking zones etc

Minor and residential roads

42

Description of road Lighting class

High speed roads with separate carriage ways Eg: motorways

Traffic density and road complexity - high - medium - low

M1 M2 M3

High speed roads, dual carriage way roads

Traffic control, separation and mix - poor - good

M1 M2

CIE 115 – Lighting Classes

43

Description of road

Lighting class

Important urban traffic roads

Traffic control, separation and mix - poor - good

M2 M3

Less important roads Eg: residential and minor roads

Traffic control, separation and mix - poor - good

M4 M5

CIE 115 – Lighting Classes

44

LIGHTCLASS All Roads

Roadswith fewJunctions

Roads withFootways

Lav. UO TI U1SurroundRatio (min.)

M1M2M3M4M5

2.0 1.5

0.750.5

1.0

0.40.40.40.40.4

1010101515

0.70.70.5--

0.50.50.5--

(min.) (min.) (min.)(max.)

CIE 115 – Lighting Classes