What is Street Lighting? – Objective, Principle, Advantages & Disadvantages

A source of light that is mounted on a lamp column or pole either on the side of the road or within the median to provide illumination is known as street lighting.

Street lighting is required along the road to have safer, comfortable, convenient and efficient movement of vehicles at night.

Objective of Street Lighting

The primary objectives of street lighting are −

• Street lighting is required to increase or enhance the community value of the street.

• Street lighting is provided along the road sides to make traffic and obstructions on the road clearly visible in order promote safety and convenience.

• Street lights also make the street more attractive.

• Street lighting improves the traffic speed and the traffic flow conditions.

Principle of Street Lighting

For designing the street lighting scheme, the following two general principles are usually employed −

• Diffusion Principle
• Specular Reflection Principle

Diffusion Principle

In the diffusion principle of design of street lighting, the lamps fitted with suitable reflectors are used. The design of the reflectors is such that they direct the light downwards and spread it as uniformly as possible over the surface of the road. To avoid the glare, the reflectors are made to have a cut-off between 30° to 45° so that the lamp filament is not visible except below the lamp.

As the surface of the road has diffusing nature causes the reflection of a certain portion of the incident light in the direction of the observer and hence the road surface appears bright to the observer.

Specular Reflection Principle

In case of specular reflection principle, the reflectors are curved upward so that the light is thrown on the road at a very large angle of incidence. In this case, the observer requires to see the objects about 30 meters away. This method of street lighting is only suitable for straight sections of the road.

This method of street lighting is more economical than diffusion method, but it suffers from the disadvantage that it produces glare for the observers.

Advantages of Street Lighting

The advantages of the street lighting are given as follows −

• Street lighting creates a pleasant atmosphere during night time.

• Street lighting prevents the illegal works and anti-social activities on the roads.

• Street lighting reduces the accident rate during night.

• Street lighting also helps in reducing the crimes at night, etc.

Disadvantages of Street Lighting

The main disadvantages of the street lighting are as follows −

• It consumes large amount of electricity.

• Sometimes it is an expensive process.

• During installation and maintenance, it may cause traffic jam, etc.

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