Road lighting design

Road Lighting

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

2

Road Lighting principle: Negative contrast

Object is seen against its background - co

luminance

ntra s

t

illuminance

3

Revealing power Visibility: ability of motorist to detect objects

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

4

Visibility of objects •

An object has to be seen against its background: the road surface • The visibility of the object depends on: – Object luminance (cd/m2)

5

Visibility of objects •

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)

6

Road luminance

luminance

illuminance

7

Design parameters Luminance ( L ) is the brightness of the road surface as seen by the driver / observer Lav Expressed in: “cd / m2”

8

Design parameters

Road Luminance (Lav)

9

Road luminance: Observer position

s

60m

w

10

Road luminance: Impact of luminance level

0.50 0.75

11

Road luminance: Key influencing factors

• Lay out • Photometry • Light source

Reflection coefficient as per Asphalt CIE R3 : Q0 = 0.07 12

LUMINANCE : Field of calculation 2 luminaires in a same row are enclosed

distance max.100m distance 60 meter height of observer 1.50m

Observer in the center of each lane 13

LUMINANCE: Position of calculation points Spacing of the points in a driving lane :

In the longitudinal direction : D = S / N

In the transverse direction : d = WL / 3

D : spacing between points in the longitudinal direction, in metres

d : spacing between points in the tranverse direction, in metres

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

WL : width of the lane, in metres

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

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

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). 14

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 lowest calculated

15

Visibility of objects •

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

16

Design parameters

Uniformity: Uo , U1 Shows how the light is distributed on the road 17

Overall uniformity: Definition

Overall uniformity is the ratio of the minimum to the average road luminance A good overall uniformity ensures that all spots on the road are sufficiently visible

18

LUMINANCE: Overall uniformity 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 19

100%

Revealing power: Impact of overall uniformity

50

75

U0=0.4

U0 =0.2 25

Uo= 0.2

0

RP

Uo= 0.4

0.1

0.2

0.5

1

2

5

10 cd/m2

Laverage 20

Overall uniformity: Key influencing factors

• Mounting height ( h ) • Spread

21

Longitudinal uniformity: Definition •

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 socalled ‘Zebra’ effect

Longitudinal Uniformity U1 = L-minimum L-maximum

22

LUMINANCE: Uniformity lengthwise Ul Calculated for each observer ; the lowest value is considered

Lmin

Lmax

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. 23

Longitudinal uniformity: Key influencing factors

• Spacing ( S ) • Throw

24

Visibility of objects •

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

25

Design parameters: Glare

Sensation caused by Brightness of lanterns within the visual field which is brighter than the adaptation level of eye. 26

Design parameters: Glare •

Disability glare reduces the vision

•

Discomfort glare creates unpleasant viewing conditions

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

27

100%

Revealing power: Impact of TI

75

UO=0.4 TI =7%

25

50

UO= 0.4 TI =30%

0

RP

0.1

0.2

0.5

1

2

5

10 cd/m2

Laverage 28

Threshold Increment Threshold increment

Assessment

% > 20 10 < 10 Operative value of TI shall be the highest value among observers.

Bad Moderate Good Key influencing factors: • Lay out • Photometry 29

Uniformity and glare

Uniform, glare-free lighting : • Early anticipation when driving • Smoother traffic flow • Relaxed drivers • Increased road capacity 30

Surround ratio: SR SR is the average horizontal illuminance on the two longitudinal strips each adjacent to the two edges of the carriageway and lying off the carriageway Divided by the average horizontal illuminance on the two longitudinal strips each adjacent to the edges of the carriageway but lying on the carriageway

SR = Ekirb / Eroad ≥ 50% Sufficient lighting in the surrounding of the road creates a proper adaptation of the eye 31

Surround ratio: SR 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 equals 5 m : 6

: luminaires

SR(1) = E1/E2

SR(2) = E4/E3

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

CIE 115 EN 13201

For dual carriageways, both carriageways together are treated as a single carriageway unless they are separated by more than 10 m. 32

Surround ratio: SR 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

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

EN 13201 33

Surround ratio: SR 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 : obstruction

: luminaires

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

EN 13201 34

Summary of lighting design parameters and related influencing factors Level

Uniformity

Glare

Visual performance

Lav

Uo

TI

Visual comfort

Lav

Ul

TI

↓ • Lay out ( h, S ) • Photometry • Light source

↓

• Lay out h → U0 S → U1 • Photometry

↓ • Lay out (h) • Photometry

35

Norms and recommendations as per CIE 115-1995

Lighting norms

Lighting Performance

Total costs

Luminance Uniformity Glare

Installation cost Maintenance cost Energy

37

Road types

Motorways 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

39

Major roads Provide main transport link within city • Motorized traffic only • Sometimes, separated carriage way provided for slow traffic or pedestrians • Pedestrian crossings at road junctions • Traffic speed 50 km/hr to 80 km/hr • Number of lanes vary from 2 * 2 to 6

40

Minor and residential roads

Provide transport link up to major road • • • •

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

41

CIE 115 – Lighting Classes Description of road High speed roads with separate carriage ways Eg: motorways High speed roads, dual carriage way roads

Lighting class Traffic density and road complexity - high - medium - low Traffic control, separation and mix - poor - good

M1 M2 M3 M1 M2 42

CIE 115 – Lighting Classes Description of road Important urban traffic roads Less important roads Eg: residential and minor roads

Lighting class Traffic control, separation and mix - poor - good Traffic control, separation and mix - poor - good

M2 M3 M4 M5 43

CIE 115 – Lighting Classes LIGHT CLASS

Roads with few Junctions

All Roads

Lav. UO TI (min.) (min.) (max.)

U1 (min.)

M1 M2 M3 M4

2.0 1.5 1.0 0.75

0.7

M5

0.5

0.4 0.4 0.4 0.4 0.4

10 10 10 15 15

0.7 0.5 -

Roads with Footways

Surround Ratio (min.) 0.5 0.5 0.5 44