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IES Street Lighting Distribution Types

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Author : Admin
Update time : 2023-12-18 14:12:33

Lighting distribution is a key factor that is frequently overlooked when we are choosing the proper LED luminaires (especially for outdoor street light).  Will the chosen luminaires adequately cover the street area we are trying to illuminate based on the position it will be installed? This is where understanding IES Distribution Types will help us make a good choice. 

IES Light Distribution:

To help lighting specifiers choose the proper fixture for their application, the Illuminating Engineering Society of North America (IES) introduced a classification system for light distribution patterns. The system consists of five “Types” (Type I– Type V , notes that Ⅰ- is a Greek symbol) that makes it easy to identify the distribution pattern of a fixture and correctly match it to the right application.  


The basis for IES Distribution Types 

IES defines the light distribution types of lamps based on longitudinal and lateral light distributions, where longitudinal light distributions are divided into 4 types: Very Short, Short, Medium, and Long; lateral light can be divided into 5 types: Type I, Type II, Type III, Type IV, and Type V.

 Street light distribution type I-V

  • Type I

The 50% light intensity curve covers the lateral width of the road, which is within 1.0 times the height of the lamps. It is the optimal choice for applications such as one or two-lane roadways, walkways, paths or sidewalks. 

  • Type II
The 50% light intensity curve covers the lateral width of the road, which is within 1.75 times the height of the lamps It is the ideal choice for wider walkways, entrance roadways, on-ramps, four-lane roadways or any area requiring long, narrow lighting. 

  • Type III
The 50% light intensity curve covers the lateral width of the road, which is within 2.75 times the height of the lampsIt is typically used for driveways, garages, and even sports fields.

  • Type IV
The 50% light intensity curve covers the lateral width of the road, which is more than 2.75 times the height of the lampsIt is the distribution type to choose if you are looking to illuminate sides of building facades, walls or parking areas.

  • Type V
The 50% light intensity curve covers a circular pattern (there is also a Type VS that produces a square distribution with a more defined angle). Having the same distribution at all lateral angles, it is perfect for general area lighting—the ideal choice if you are looking to do parking lots or intersections. 

  • Type Very Short
The 50% light intensity curve covers the longitudinal width of the road, which is within 1.0 times the height of the lamps.

  • Type Short
The 50% light intensity curve covers the longitudinal width of the road, which is within 2.25 times the height of the lamps.

  • Type Medium
The 50% light intensity curve covers the longitudinal width of the road, which is within 3.75 times the height of the lamps.

  • Type Long
The 50% light intensity curve covers the longitudinal width of the road, which is more than 3.75 times the height of the lamps.
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