IES Street Lighting Distribution Types

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-Ⅴ 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.

• 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

• Type III

• Type IV

• Type V

• Type Very Short

• Type Short

• Type Medium

• Type Long