March, 2022

Different types of light distribution for street & roadway lighting

LED street and roadway lighting is a cost-effective and sustainable choice for cities today, it significantly reduces energy cost and maintenance cost as well as ensures drivers and pedestrians alike feel safe, comfortable and not isolated.

There are lots of important factors to focus on when choosing the right LED street lights. Lumen output, mechanical design, thermal management, driver performance, color temperature, control option, all of them are important. But how about light distribution type?

Light distribution is basically the projected pattern of a luminaire will illuminate onto a surface. Choosing the correct light distribution type for outdoor streets and roadways is as important as choosing the correct power or color temperature.

There are mainly 5 light distribution types for different applications:

Type I

Type I light distribution delivers a wide, symmetrical light for luminaires located in the middle of a walkway. The width of the pattern it creates is about equal to the fixture’s height.

  • Walkways
  • Paths
  • Sidewalks

Type II

Type II luminaires feature a slightly wider distribution and are intended for installations where the luminaire is located at the edge of the roadway. They illuminate an area up to 1.5 times wider than the mounting height of the luminaire. For example, if the luminaire is 10 feet high, it will cast light up to 15 feet wide on the area below.

  • Wide walkways
  • Entrance rodaways

Type III

Type III light distribution casts light about 2.75 times wider than the mounting height of the luminaire. Luminaires should be placed along the side of the area to be lit, allowing the light to project outward. A luminaire with Type III distribution mounted to 10-feet pole will cast light about 27.5 feet in width from the light source.

  • Roadways
  • Parking areas

Type IV

Type IV luminaires are known as forward throw or asymmetric illumination. Like Type III luminaires, they will cast light 2.75 times wider than their height, but produces a more rounded distribution pattern that pushes the light outward, will little light falling behind the luminaire. They can be mounted on walls or used to illuminate specific areas.

  • Parking areas
  • Building sideways

Type V

Type V luminaire delivers a circular distribution that has the same intensity at all angles. This distribution has a circular symmetry of candlepower that is essentially the same at all lateral angles.

  • Center roadways
  • Parking areas