ILLUMINATION ENGINEERING - PART – 15 – ROAD AND STREET LIGHTING AND THREE PROBLEMS

ROAD 
A general term denoting any public way for purposes of vehicular traffic.

TYPES OF ROAD

1. Ring road – A road an urban area enabling traffic to avoid going to urban centre.

2. Radial road – A road providing direct communication between the centre of an urban area and outer districts. 

3. Collector Road – A link between the radial or ring roads and the local distribution access streets.

4. Trunk Road – A main route in the through communication system of a country.

5. Express Road – A road has no stopping and parking areas.

6. All-purpose Road – Road usable by all traffic including pedestrians and cyclists. Used for to distinguish other roads from motor ways.

STREET, ALLEY, AVENUE AND BOULEVARD ALL REFER TO PUBLIC WAYS OR ROADS IN MUNICIPAL AREAS.

STREET is a round which has become partly or wholly defined by buildings along one or both. 

[OR]  

A STREET is a road in a village, town, or city, especially a road lined with buildings. 

ALLEY is a narrow street or foot way, especially at the rear of or between rows of buildings or lots. 

AVENUE is properly a prominent street, often one bordered by fine residences and impressive buildings, or with a row of trees on each side. 

A BOULEVARD is a beautiful, broad street, lined with rows of stately trees, especially used as a promenade (a public area set aside as a pedestrian walk). 

TYPE OF STREETS  

RESIDENTIAL STREET 

Street with the majority of frontages comprising private houses.

SHOPPING STREET 

Street with frontage comprising a high proportion of shops or other premises which may be lit at night and with heavy pedestrian.

COMMERCIAL STREET 

Street with frontage comprising a high proportion of commercial high proportion of commercial premises usually unlit at night and with a high proportion of heavy goods vehicles in the traffic stream.

WAY - A line leading to a place or point

TYPES OF WAY

1. HIGH WAY – A way for the passage of vehicular traffic over which such traffic way may lawfully pass.

2. CARRIAGE WAY – That portion of high way intended primarily for vehicular traffic.

3. DUAL CARRIAGE WAY – A layout of the separated carriage ways, each reserved for traffic in one direction only.

4. FOOT WAY – The portion of a road reserved exclusively for pedestrians.

STREET LIGHTING 

Street lighting is intended to create an environment at nighttime in which people can see comfortably and can quickly and accurately identify objects on traveled roadways.  Street lighting can improve, safeguard, facilitate, and encourage vehicular and pedestrian traffic.

OBJECTIVES OF STREET LIGHTING

1. Good outdoor lighting can create and encourage a pedestrian friendly environment, which is especially beneficial to neighborhood business districts. 

2. Pedestrian lighting improves walkway illumination for pedestrian traffic and enhances community safety and business exposure. 

3. Lighting for pedestrians is especially important along Main Streets, Mixed Use Streets and Local Connectors, and in other locations where the land use supports large volumes of pedestrians and vehicles.

AVERAGE RECOMMENDED ILLUMINANCE

Outdoor average sunlight ranges from 32 000 to 100 000 lux

Warehouse aisles (a long narrow passage) are lit to approximately 100-200 lux

A bright office requires about 400 lux of illumination

At sunset and sunrise (with a clear sky), ambient outdoor light is also about 400 lux

Building corridors can be lit adequately at around 100 lux

Moonlight represents about 1 lux.

LAMPS USED IN STREET LIGHTING 

1. INCANDESCENT BULB 

A 100 W Incandescent bulb – for general task lighting applications: 1700 lumens output

and its efficacy is 17 lumens/watt

2. FLUORESCENT LAMP 

A 40 W Fluorescent tube – for highly suitable for downtown areas and parking lots and office ceiling lighting - 1600 lumens output and its and its lamp efficacy is 50 lumens/watt

3. HIGH PRESSURE SODIUM LAMP

A 150 W High pressure sodium bulb – for street/area lighting - 12000 lumens output and its efficacy is 80 lumens/watt

4. HALIDE LAMP 

A 400 W Metal Halide lamp - for high bay warehouse lighting: 38000 lumens output and its efficacy is 95 lumens/watt

THE LIGHT OUTPUT RATIO OF A LIGHT FITTING 

This term is defined as the ratio of the total amount of light output of a light fitting (containing a lamp) to that of just the bare lamp. 

When the lamp is placed in a fitting losses of light will occur – this is because with most artificial light sources on the market light is radiated in all directions. 

LUMEN DEPRECIATION OF THE LIGHT SOURCE

Lumen depreciation is a process of the gradual decline in light output that is observed from most light sources over time due to gradual filament or electrode deterioration and blackening of the lamp.

PROBLEMS - 01 

Calculate the spacing distance between two poles having the following details. 

Pole height = 26 feet, width of the road = 2 feet, wattage of each luminaire = 250 W, required lumen = 10 lux, coefficient of utilization = 0.8, lamp, Lamp lumen Depreciation Factor (LLDF)  = 0.9,  and depreciation factor i = 0.8. 

Space to height ratio should be less than three.

PROBLEMS - 02

Calculate the streetlight watt of each luminaire of street light pole having details.

40 W Fluorescent lamp luminous efficacy = 50 lm per watt, Width of the road is 12 feet, distance between each pole = 36 feet, required illumination levels for street light = 6.46 lux per square metre, maintenance factor = 0.29.

Space to height ratio should be less than three.

PROBLEM - 03 

Calculate the power required of a street light for the following streetlight area (fluorescent lighting).

Required illumination level for street light = 6.46 lux per square metre, luminous efficacy of fluorescent light = 50 lumen per watt and required streetlight area to be illuminated = 1 square metre.