Chapter 10 Street Lighting

24010 Street Lighting Design

Chapter 10

Street lighting Design

Chapter content:

(1.0)Introduction

(2.0)Factors affecting the design of street lighting

(3.0)Street lighting arrangements

(4.0)Street lighting design process

(5.0)Types of lamps used in Street lighting

(6.0)Methods of switching of lamps

(7.0)Street lighting system

(8.0)Lighting control and Wiring system

(9.0)Design of the street lighting scheme


Chapter 10

Street lighting Design

(1.0)Introduction:

Lighting is a vital rule to describe the importance of major and minor roads, which constitute the lifelines of communication in the motorized world today.

For these roads, to fulfill their function properly, they must be made as safe as technological and economic resources will permit. And one of the most effective instruments in the constant striving to create saver roads is light. Lighting for guidance, lighting to reveal all the features of roads and point up hazards. Lighting to aid perception and provide clear visual information for both drivers and pedestrians.

So we can say that the basic purpose of street lighting is to promote safety and convenience on the streets at night through adequate visibility, and to promote civic progress. Statistics show that good street lighting installations results in:

Reduce traffic accidents Combat crime Respect the environment

(2.0)Classification of factors affecting the design of street lighting:

(2.1)Area classification:

(2.1.1)Commercial:

That portion of a municipality in a business development where ordinarily there are large numbers of pedestrians during business hours. This definition applies to densely developed business areas outside, as well as within, the central part of a municipality. The area contains land use, which attracts a relatively heavy volume of nighttime vehicular and/or pedestrian traffic on a frequent basis.


(2.1.2)Intermediate:

That portion of a municipality is often characterized by a moderately heavy nighttime pedestrian activity such as in blocks having libraries, community recreation centers, large apartment buildings or neighborhood retail stores.

(2.1.3)Residential:

A residential development or a mixture of residential and commercial establishments is characterized by a few pedestrians at night. This definition includes areas with single family homes, town houses, and/or small apartment buildings.

(2.2)Roadway classification:

(2.2.1)Freeway:

It’s a divided major roadway with full control of access and with no crossings at grade. This definition applies to toll as well as non-toll roads.

(2.2.2)Expressway:

It’s a divided major roadway for through traffic with partial control of access and generally with interchanges at major crossroads. Expressways for non-commercial traffic within parks and park-like areas are generally known as parkways.

(2.2.3) Arterial:

The part of the roadway system that serves as the principal network for through traffic flow. The routes connect areas of principal traffic generation and important rural highways entering the city.


(2.2.4)Collector:

The distributor and collector roadways serving traffic between major and local roadways. These are roadways used mainly for traffic movements within residential, commercial and industrial areas.

(2.2.5)Local:

Roadways used primarily for direct access to residential, commercial, industrial, or other abutting property. They do not include roadways carrying through traffic. Long local roadways will generally be divided into short sections by collector roadway systems.

(2.2.6)Alleys:

These are narrow public ways within a block, generally used for vehicular access to the rear of abutting properties.

(3.0)Street lighting arrangements:

(3.1)Two way traffic roads:

There are four basic types of street lighting arrangements, which we can summarize in the following points.

(3.1.1)Single sided:

This type of arrangement, in which all luminaries are located on one side of the road, is used only when the width of the road is equal to, or less than the mounting height of the luminaries.

Fig 10.1: Single sided arrangement


(3.1.2)Staggered:

This type of arrangement in which the luminaries are located on both sides of the road in a staggered, or zigzag, arrangement is used mainly when the width of the road is between 1 to 1.5 times the mounting height of the luminaries.

Fig 10.2: Staggered arrangement

(3.1.3)Opposite:

This type of arrangement, with the luminaries located on both sides of the road opposite to one another, is used mainly when the width of the road is greater than 1.5 times the mounting height of the luminaries.

Fig 10.3 Opposite arrangement


(3.1.4)Span wire:

This type of arrangement, with the luminaries suspended along the axis of the road, is normally used for narrow roads that have buildings on both sides.

Fig 10.4: Span wire arrangement

(3.2)Curves:

Curves of large radius (in the order of 300 m) can be treated as straight roads and the luminaries can be sited in accordance with one of the schemes outlined above.

The locations of luminaries on curves of smaller radius, however, should be such as to ensure both adequate road-surface luminance and effective visual guidance. Where the width of the road is 1.5 m less than the mounting height, the luminaries should be placed above the outside of the curve in a single sided arrangement.

For wider roads an opposite arrangement should be used since the staggered arrangement gives visual guidance, and should therefore be avoided.


(4.0)Street lighting design process:

The illumination design process involves the selection of the proper lighting equipment and the establishment of the geometry of the system in order to provide the most effective lighting system to satisfy the needs.

(4.1)The major steps of the design process are outlined as follows:

(4.1.1)Existing conditions:

Determination of roadway facility and land use area classifications.

(4.1.2)Selection of illumination level:

The recommended average intensity of horizontal illumination may be determined based upon the classifications of roadway facility and area type.

Table 11.1 shows the recommended average maintained illumination

(In foot candles).

VEHICULAR ROADWAY

CLASSIFICATION

AREA CLASSIFICATION

Commercial intermediate residential

Freeway 0.6 0.6 0.6

Expressway 1.4 1.2 1

Major ( arterial ) 2 1.4 1

Collector 1.2 0.9 0.6

Local 0.9 0.6 0.4

Alley 0.6 0.4 0.4

Table 10.1 recommended average maintained illumination (in foot candles).


(4.1.3)System characteristics:

Detailed calculations using selected lighting source types and sizes and luminaires mounting heights and spacing locations are employed in order to determine the average intensity of horizontal illumination. The uniformity of illumination is checked by comparing the ratio of average maintained illumination to minimum maintained illumination, commonly referred to as the uniformity ratio, with the recommended criteria in order to determine optimal effectiveness of lighting system.

(5.0)Types of lamps used in Street lighting:

We have to choose suitable kinds of lamps for different streets. The lamp must be convenient for vehicles and pedestrians.

In internal streets we used mercury lamps to give a white colour, with enough levels of levels of average luminance to promote civic progress, and ensure pedestrians safety.

On highways, where there are no pedestrians, we use high-pressure sodium lamps. Its yellow light is suitable for such kinds of lighting, even in cloudy weather. The human eye is very sensitive to yellow light, e.g. SHP- 400 watt, 47000Lm, 118 Lm/watt.

(5.1)High pressure sodium lamps:

The high-pressure sodium discharge lamp is a lamp providing the highest efficiency in a light source with a good colour rendition. The high-pressure sodium discharge is enclosed in an arc-tube envelope of high temperature, alkali-vapour resisting high density, polycrystalline alumina.

The difference from the former low-pressure sodium lamp is that the sodium pressure, with high volume loading, results in a well stabilized discharge and maximum efficiency.

The high- pressure sodium discharge lamp has an initial efficacy in excess of 100 lumens per watt. Median lamp live is in order of 6000 hours but may be expected to improve with improved construction techniques.

High efficiency with acceptable color and a small, high brightness source with low ultraviolet radiation make the high-pressure sodium lamp attractive as a lighting source for street, roadway and area lighting.


(5.2)Low pressure sodium lamps:

This type of lamp has special purposes because they give very strong light under small power. This type of lamps has dark yellow light and is used in tunnels and closed public places. They also have relatively long life.

(5.3)Metal halide lamps:

This is a very special purpose lamp it has special advantage that it can response very fast to electric power when turning on and very slow when turning off, i.e. it turns on quickly and turn off slowly. Thus this type of lamps could be used in medical operation room and flood lighting. e.g. HSLL-BW-400, 400 watt, 2300 lm/watt.

(5.4)Mercury lamps:

There are several types of mercury lamps such as high-pressure, low pressure and compound mercury lamps. This type has special applications.

It gives a bright white light thus it could be used in illumination of open places such as large stadiums since this type of lamps have strong glass, they should be put when they should be hanged over large arm poles and must be used in clear weather.


(6.0)Methods of switching of lamps:

There are various methods, some of which are:

a) Photo cellb) Control switchc) Timer

(7.0)Street lighting system:

The distribution lighting network consists of:

1. Lighting distribution box2. Poles3. Lighting luminaires4. Cables

(7.1)Lighting distribution box (LDB):

The LDB is a pad-mounted-explosion proof type provided with the following equipment and devices.

a) One incoming C.B.b) Four outgoing circuit breakers.c) One KWH meterd) Automatic contactor (photocell or timer)

The lighting distribution box is shown in fig 10.5.


Fig 10.5 :Lighting Distribution Box


(7.2) Poles:

There is a wide range of street lighting poles which can be classified according to their height (15m, 12m, 10m, 8m, ……3m) or according to their type (stepped, octagonal, ….., or round).

The poles of 10m height are used in lighting system for most of streets in the neighborhood, and the poles of 3m height are mainly used for gardens lighting. For highways, higher poles are used to fulfill the required lighting characteristics.

Fig 10.6 shows the main construction of poles used in street lighting.

Fig 10.6: Construction of street lighting poles


The total pole heights depend on the method of installation. The manufacturer should increase the pole height by at least 1-5m if it’s directly mounted in soil or in concrete. Fig 10.7 shows the recommended type of lighting poles (10m high)

Fig 10.7 : The 10m high pole used in street lighting


The 3m poles are of decorative or round types. This is shown in fig 10.8.

Fig 10.8 The 3m high poles used in gardens

Each pole should be provided with a door opening for cable connection at a height not less than 80 cm from ground level.


(7.3)Lighting luminaires:

The street lighting designed here is to use several types of luminaires. Their type of lamps is:

250, 400 watt high pressure sodium vapour lamps. 160 watt mercury lamps.

Different shapes of luminaires are shown in fig 10.9.

Fig 10.9 Different shapes of luminaires


(7.4)Cables:

Cables of aluminum types should be used to connect the low voltage side of distribution transformer to the lighting distribution box (LDB), and the cross sectional area of cables is chosen according to the lighting loads and the rating of the lighting distribution box (LDB).

Cables of 2-mm² copper are used to connect power cables and luminaires.

(8.0)Lighting control and Wiring system:

(8.1)On-off control:

Luminaires for dusk to dawn operation will normally be controlled by a photoelectric cell installed on each luminaire, however, central control may be more economical for luminaires having fixed hours of operation.

An automatic system using a time switch with an astronomical dial or a manual on-off control will be used for such cases.

(8.2)Type of system:

Multiple wiring systems will be installed, except for extensions to existing series systems or for long access roads where voltage drops exceeding that permitted for multiple lighting systems would occur.

Circuits for multiple lighting will be designed to utilize the highest low-voltage level appropriate for the installation in order to keep wire sizes and voltage drops to a minimum.

Lamps will be connected phase-to-neutral rather than phase-to-phase. Where practicable, units will be connected to transformers, which serve other loads. Also protection and disconnection of lighting circuits will be provided.

(8.3)Grounding:

All lighting circuits will include an equipment grounding conductor. The equipment grounding conductor may be any conductor approved by the NEC, and will be bonded to the non-current-carrying metal parts of each lighting standard and luminaire.


(9.0)Design of the street lighting scheme:

1. We specify the width, we have in our plan.2. Substitute in following equation:

E =

F×C .F .×M . F .S×W

Where:

F: is lamp flux in lumens

CF: is the clearing factor, taken about 0.6

MF: is the maintenance factor, taken about 0.7

S: is the space between the poles in meter.

T: is the street width in meter.

E: is the illumination level of street in lux

3. The Span is taken from tables of EGY LUX catalogue according to the street type .

4. The illumination level varies according to the street width and is taken from tables EGY LUX catalogue

5. As we know the street width from the plan we can calculate the lamp flux, then we go to the tables and find most suitable lamp wattage to the nearest standard lumen.

6. Chose a symbol for each type of pole then plot the chosen design on the plan of the area. When passing by curved port of street multiply the calculate space by a factor 0.8.

7. Make sure that the pole length is 3, 6, 8, 10, 12 or 14 meter for high pressure sodium lamps while the arms are 0, 1.5, 2.5 or 5 meter. Also the span must not be more than 45 meters and for an average of 20-30 meters.

8. Gardens and green area doesn't obey these lays of illumination since they are illuminated for decoration only, so we put their poles according to public view of the place taking a lamp of 70 watt for each luminaire.

Documents

Chapter 10 Street Lighting